Optical property measurement apparatus and optical property measurement method

Abstract

To measure at least two kinds of optical characteristics by using one device.SOLUTION: A pulse forming part 3 generates pulse light PL and can change a time waveform of the pulse light PL according to types of optical characteristics to be measured. A waveform measurement part 5 measures the time waveform of the pulse light PL outputted from a measurement object B after being applied to the measurement object B. An optical system 4 has a dimming part 41 which has an attenuation factor for one wavelength component composing the pulse light PL larger than an attenuation factor for another wavelength component composing the pulse light PL. The optical system 4 can switch between a first state in which the dimming part 41 is disposed on an optical path of the pulse light PL outputted from the measurement object B and a second state in which the dimming part 41 is not disposed on the optical path. An analysis part 6 obtains optical characteristics of the measuring object B on the basis of the time waveform measured by the waveform measurement part 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical property measurement apparatus and an optical property measurement method.

Background Art

[0002] Patent Document 1 discloses a technique related to a dispersion measurement apparatus. This dispersion measurement apparatus includes a pulse formation unit, a correlation optical system, a light detection unit, and a calculation unit. The pulse formation unit forms an optical pulse train including a plurality of second optical pulses having a time difference from each other and different center wavelengths from a first optical pulse output from a measurement target. The correlation optical system receives the optical pulse train output from the pulse formation unit and outputs correlation light including the mutual correlation or autocorrelation of the optical pulse train. The light detection unit detects the time waveform of the correlation light. The calculation unit estimates the wavelength dispersion amount of the measurement target based on the feature amount of the time waveform.

[0003] Non-Patent Document 1 discloses time-resolved spectroscopic measurement. In the method described in this document, the time response of a sample is evaluated by changing the time difference between a pump light that excites the sample and a probe light that detects a change in the characteristics of the sample. Non-Patent Document 2 discloses a time-resolved measurement method using a plurality of optical pulses having different center wavelengths from each other. In the method described in this document, wavelength conversion is performed using an optical parametric amplifier (OPA) to generate a plurality of optical pulses having different wavelengths from each other.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] When measuring the optical properties of a measurement object by irradiating the measurement object with pulsed light, different devices are used depending on the type of optical property to be measured. For example, a device (time response measurement device) is known that irradiates a measurement object with pump light and probe light having different wavelengths, and evaluates the characteristic changes inside the measurement object caused by the irradiation of the pump light based on the time change of the probe light output from the measurement object. In addition, a device is known that irradiates a measurement object with an optical pulse train including a plurality of optical pulses having a time difference and different central wavelengths, and estimates the wavelength dispersion amount of the measurement object based on the feature amount (for example, pulse interval) of the time waveform of the optical pulse train that has passed through the measurement object (see, for example, Patent Document 1). Therefore, when it is desired to measure two or more types of optical properties, it is necessary to prepare two or more devices according to the type of each optical property.

[0007] In view of such problems, the present disclosure has been made, and an object thereof is to provide an optical property measurement device and an optical property measurement method capable of measuring two or more types of optical properties, for example, time response measurement and wavelength dispersion measurement, using a single device. [Means for Solving the Problems]

[0008] The optical property measuring apparatus according to the present disclosure is an apparatus that measures the optical properties of a measurement object, and includes a pulse forming unit, a waveform measuring unit, an optical system, and an analysis unit. The pulse forming unit generates pulsed light and can change the temporal waveform of the pulsed light according to the type of optical property to be measured. The waveform measuring unit measures the temporal waveform of the pulsed light output from the measurement object after being irradiated on the measurement object. The optical system has a light attenuation unit in which the attenuation rate for one wavelength component constituting the pulsed light is greater than the attenuation rate for another wavelength component constituting the pulsed light. The optical system can mutually switch between a first state in which the light attenuation unit is disposed on the optical path of the pulsed light output from the measurement object and a second state in which the light attenuation unit is not disposed on the optical path. The analysis unit obtains the optical properties of the measurement object based on the temporal waveform.

[0009] The optical property measuring method according to the present disclosure is a method of irradiating a measurement object with pulsed light to measure the optical properties of the measurement object, and includes: a step of selecting either a first state in which a light attenuation unit in which the attenuation rate for one wavelength component constituting the pulsed light is greater than the attenuation rate for another wavelength component constituting the pulsed light is disposed on the optical path of the pulsed light output from the measurement object or a second state in which the light attenuation unit is not disposed on the optical path in an optical system capable of mutually switching between the two states; a step of irradiating the measurement object with pulsed light having a temporal waveform corresponding to the type of optical property to be measured by using a pulse forming unit capable of changing the temporal waveform of the pulsed light; a step of measuring the temporal waveform of the pulsed light that has passed through the optical system; and a step of obtaining the optical properties of the measurement object based on the temporal waveform.

[0010] In these apparatuses and methods, a pulse forming unit capable of changing the temporal waveform of pulsed light is used to set the temporal waveform according to the type of optical property to be measured. Further, an optical system capable of mutually switching between a first state in which an optical attenuator is disposed on the optical path of the pulsed light output from the measurement object and a second state in which no optical attenuator is disposed on the optical path is used to set the presence or absence of the optical attenuator on the optical path. The attenuation rate of the optical attenuator with respect to one wavelength component constituting the pulsed light is greater than the attenuation rate of the optical attenuator with respect to another wavelength component constituting the pulsed light. Therefore, measurement of an optical property (for example, time response measurement) that requires attenuation of one wavelength component constituting the pulsed light after passing through the measurement object and measurement of an optical property (for example, wavelength dispersion measurement) that does not require attenuation after passing through the measurement object can be performed using a single apparatus. Thus, measurement of two or more types of optical properties, for example, time response measurement and wavelength dispersion measurement, can be performed using a single apparatus.

[0011] In the optical system of the above apparatus, the optical attenuator may be movable in a direction intersecting the optical axis of the pulsed light. Alternatively, the optical system may have a configuration for mutually switching between two optical paths for the pulsed light, and the optical attenuator may be disposed on either one of the two optical paths. By the optical system having any of these configurations, it is possible to easily switch between a first state in which the optical attenuator is disposed on the optical path and a second state in which no optical attenuator is disposed on the optical path.

[0012] In the above-described apparatus, the types of optical characteristics to be measured include the time response inside the object to be measured due to light irradiation and the amount of wavelength dispersion of the object to be measured. The optical system may be in a first state during the measurement of the time response and in a second state during the measurement of the amount of wavelength dispersion. Similarly, in the above-described method, the types of optical characteristics to be measured include the time response inside the object to be measured due to light irradiation and the amount of wavelength dispersion of the object to be measured. In the step of selecting the state, the first state may be selected during the measurement of the time response, and the second state may be selected during the measurement of the amount of wavelength dispersion. During the measurement of the time response, it is desirable to irradiate the object to be measured with pump light and probe light having different wavelengths, and then remove the pump light and measure only the probe light. In this case, the pump light corresponds to one wavelength component, and the probe light corresponds to another wavelength component. Further, during the measurement of the amount of wavelength dispersion, it is desirable to irradiate the object to be measured with an optical pulse train including a plurality of optical pulses having different wavelengths, and detect the time waveform of the optical pulse train that has passed through the object to be measured while maintaining the light intensity ratio of each wavelength component. By selecting the first state during the measurement of the time response and the second state during the measurement of the amount of wavelength dispersion in the optical system and the step of selecting the state, the time response measurement and the wavelength dispersion measurement can be suitably performed.

[0013] In the above-described apparatus, the pulse forming unit may generate, as pulse light, a first pulse light including the wavelength of the pump light, a second pulse light including the wavelength of the probe light, and a third pulse light including the wavelengths of the pump light and the probe light on a common optical axis during the measurement of the time response. The attenuation rate of the attenuation unit with respect to the pump light may be greater than the attenuation rate of the attenuation unit with respect to the probe light. The waveform measurement unit may measure a first time waveform that is the time waveform of the first pulse light that has passed through the attenuation unit, a second time waveform that is the time waveform of the second pulse light that has passed through the attenuation unit, and a third time waveform that is the time waveform of the third pulse light that has passed through the attenuation unit. The analysis unit may obtain the time response of the object to be measured based on the first time waveform, the second time waveform, and the third time waveform.

[0014] In the above method, when measuring the time response, the steps of irradiation and measurement are alternately repeated. In one irradiation step, a first pulsed light, which is a pulsed light including the wavelength of the pump light, is irradiated onto the object to be measured along a predetermined optical axis. In the subsequent measurement step following the irradiation step, a first time waveform, which is the time waveform of the first pulsed light output from the object to be measured and then passing through the light attenuation unit, is measured. In another irradiation step, a second pulsed light, which is a pulsed light including the wavelength of the probe light, is irradiated onto the object to be measured along a predetermined optical axis. In the subsequent measurement step following the irradiation step, a second time waveform, which is the time waveform of the second pulsed light output from the object to be measured and then passing through the light attenuation unit, is measured. In yet another irradiation step, a third pulsed light, which is a pulsed light including the wavelengths of the pump light and the probe light, is irradiated onto the object to be measured along a predetermined optical axis. In the subsequent measurement step following the irradiation step, a third time waveform, which is the time waveform of the third pulsed light output from the object to be measured and then passing through the light attenuation unit, is measured. In the step of obtaining the optical characteristics of the object to be measured, the time response of the object to be measured may be obtained based on the first time waveform, the second time waveform, and the third time waveform.

[0015] When the optical axes of the pump light and the probe light are made to coincide without being inclined with respect to each other, and the pump light and the probe light are irradiated onto an object to be measured arranged on the coincident optical axis, the probe light is detected as light with the pump light superimposed thereon. In order to measure the time response inside the object to be measured caused by the irradiation of the pump light with the probe light, it is desirable to eliminate the influence of the pump light from the detection result. Therefore, it is conceivable to remove only the pump light from the pump light and the probe light that have passed through the object to be measured. However, usually, the light intensity of the pump light is much larger than that of the probe light, so it is difficult to remove the pump light to such an extent that it can be ignored with respect to the probe light. In one example, the light intensity of the pump light is approximately 100 times that of the probe light. Therefore, for example, even if only the pump light is attenuated using a wavelength filter with an attenuation rate of 99%, pump light with a light intensity almost the same as that of the probe light remains.

[0016] Therefore, in the above-described apparatus and method, a first pulsed light including the wavelength of the pump light, a second pulsed light including the wavelength of the probe light, and a third pulsed light including the wavelengths of the pump light and the probe light are generated on a common optical axis. Then, after these first pulsed light, second pulsed light, and third pulsed light are irradiated onto the measurement object on the optical axis, the light intensity attenuator attenuates the light intensity of the light having the wavelength of the pump light. Therefore, the first time waveform, which is the time waveform of the first pulsed light that has passed through the light intensity attenuator, includes only the time waveform of the attenuated pump light. Further, the second time waveform, which is the time waveform of the second pulsed light that has passed through the light intensity attenuator, includes only the time waveform of the probe light when the pump light is not irradiated. Further, the third time waveform, which is the time waveform of the third pulsed light that has passed through the light intensity attenuator, includes a time waveform in which the time waveform of the probe light when the pump light is irradiated and the time waveform of the attenuated pump light are superimposed. Based on these time waveforms, it is possible to obtain the time response inside the measurement object due to the irradiation of the pump light from the time waveform of the probe light while excluding the influence of the pump light by calculation.

[0017] In the above-described apparatus, the analysis unit may obtain the time response of the measurement object based on the comparison between the difference between the third time waveform and the first time waveform and the second time waveform. Similarly, in the above-described method, in the step of obtaining the optical characteristics, the time response of the measurement object may be obtained based on the comparison between the difference between the third time waveform and the first time waveform and the second time waveform. By calculating the difference between the third time waveform and the first time waveform, it is possible to obtain the time waveform of the probe light when the pump light is irradiated while excluding the influence of the pump light. Then, by comparing this difference with the second time waveform, which is the time waveform of the probe light when the pump light is not irradiated, the time response inside the measurement object can be obtained more accurately.

[0018] In the pulse forming unit of the above-described apparatus, the time interval between the intensity peak of the component of the wavelength of the pump light included in the third pulsed light and the intensity peak of the component of the wavelength of the probe light may be variable. In this case, it is possible to easily set the time interval between the pump light and the probe light included in the third pulsed light appropriately according to the type or property of the measurement object.

[0019] In the pulse forming section of the above-described apparatus, the ratio of the pulse width of the wavelength component of the pump light included in the third pulse light to the pulse width of the wavelength component of the probe light may be variable. In this case, it is possible to easily set appropriately the ratio of the pulse width of the pump light included in the third pulse light to the pulse width of the probe light according to the type or property of the object to be measured.

[0020] In the above-described apparatus, the pulse width of the wavelength component of the pump light included in the third pulse light may be smaller than the pulse width of the wavelength component of the probe light included in the third pulse light. Similarly, in the above-described method, the pulse width of the wavelength component of the pump light included in the third pulse light may be made smaller than the pulse width of the wavelength component of the probe light included in the third pulse light. In this case, for example, compared with a method of detecting the probe light a plurality of times while changing the time difference between the probe light having a width comparable to the width of the pump light and the pump light, the measurement operation can be further simplified.

[0021] In the above-described method, the third time waveform may be measured after measuring the first time waveform and the second time waveform. The light intensity of the third pulse light is greater than the light intensity of each of the first pulse light and the second pulse light. Depending on the object to be measured, irreversible characteristic changes may occur by irradiating light having a large light intensity. In such a case, if the measurement of the third time waveform is performed prior to at least one of the measurement of the first time waveform and the measurement of the second time waveform, the first time waveform and / or the second time waveform measured thereafter may lack accuracy. By performing the measurement of the third time waveform after the measurement of the first time waveform and the measurement of the second time waveform, such a concern can be reduced.

[0022] In the above-described apparatus, when measuring the amount of wavelength dispersion, the pulse forming unit may form an optical pulse train including a plurality of pulses having a time difference from each other and different central wavelengths as pulse light. The waveform measuring unit may measure the time waveform of the optical pulse train that has passed through the object to be measured. The analysis unit may estimate the amount of wavelength dispersion of the object to be measured based on the characteristic amount of the time waveform of the optical pulse train. Similarly, when measuring the amount of wavelength dispersion in the above-described method, in the irradiating step, an optical pulse train including a plurality of pulses having a time difference from each other and different central wavelengths is irradiated onto the object to be measured as pulse light, in the measuring step, the time waveform of the optical pulse train that has passed through the object to be measured is measured, and in the step of obtaining the optical characteristics, the amount of wavelength dispersion of the object to be measured may be estimated based on the characteristic amount of the time waveform of the optical pulse train. For example, by these apparatuses and methods, the amount of wavelength dispersion of the object to be measured can be suitably measured.

[0023] In the above-described apparatus, the pulse forming unit may have a spatial light modulator that generates pulse light by performing at least one of phase modulation and intensity modulation of the input light. In this case, since the time waveform of the pulse light can be changed only by changing the modulation pattern displayed on the spatial light modulator, it is possible to easily generate pulse light having a time waveform corresponding to the type of optical characteristic to be measured.

[0024] In the above-described apparatus, the waveform measuring unit may be disposed between the object to be measured and the optical system or at a subsequent stage of the optical system, and may have a correlation optical system that converts the pulse light into correlation light including cross-correlation or auto-correlation. The analysis unit may obtain the optical characteristics of the object to be measured based on the pulse light converted into correlation light. Alternatively, the waveform measuring unit may be disposed between the object to be measured and the optical system or at a subsequent stage of the optical system, and may have an optical component that extends the time width of the pulse light. In these cases, even if the time width of the pulse light is, for example, on the order of femtoseconds or picoseconds, the time waveform can be accurately measured. Therefore, the optical characteristics of the object to be measured can be accurately measured.

[0025] In the above-described apparatus and method, the light attenuation unit may include a wavelength filter that includes the wavelength of one wavelength component within a blocking band and includes the wavelength of another wavelength component within a transmission band. In this case, the light intensity of one wavelength component can be attenuated with a simple configuration.

Advantages of the Invention

[0026] According to the optical property measurement apparatus and the optical property measurement method of the present disclosure, measurement of two or more types of optical properties, for example, time response measurement and wavelength dispersion measurement, can be performed using a single apparatus.

Brief Description of the Drawings

[0027]

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DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of an optical property measurement apparatus and an optical property measurement method according to the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are assigned to the same elements, and redundant descriptions are omitted. In the present disclosure, the time waveform means a time waveform related to the light intensity unless otherwise specified.

[0029] FIG. 1 is a diagram schematically showing the configuration of an optical property measurement apparatus 1A according to an embodiment of the present disclosure. This optical property measurement apparatus 1A can measure a plurality of optical properties of a measurement object B with a single apparatus. The plurality of optical properties include both the time response inside the measurement object B caused by light irradiation and the wavelength dispersion amount of the measurement object B. The optical property measurement apparatus 1A includes a pulse laser light source 2, a pulse forming unit 3, an optical system 4, a waveform measurement unit 5, and an analysis unit 6.

[0030] The light input end 3a of the pulse forming unit 3 is optically coupled to the pulse laser light source 2 spatially or via an optical waveguide such as an optical fiber. The light output end 3b of the pulse forming unit 3 is optically coupled to the measurement object B spatially or via an optical waveguide such as an optical fiber. Further, the measurement object B is optically coupled to the waveform measurement unit 5 spatially or via an optical waveguide such as an optical fiber. The optical system 4 is disposed on the optical path between the measurement object B and the waveform measurement unit 5. The analysis unit 6 is electrically connected to the waveform measurement unit 5.

[0031] The pulse laser light source 2 outputs coherent initial pulse light Pa. The pulse laser light source 2 is, for example, a femtosecond laser, and in one embodiment, is a solid laser light source such as an LD directly excited type Yb:YAG pulse laser. The time waveform of the initial pulse light Pa is, for example, Gaussian-shaped. The full width at half maximum (FWHM) of the initial pulse light Pa is, for example, in the range of 10 fs to 10,000 fs, and in one example, is 100 fs. This initial pulse light Pa is an optical pulse having a certain bandwidth and includes a plurality of continuous wavelength components. In one embodiment, the bandwidth of the initial pulse light Pa is 10 nm, and the central wavelength of the initial pulse light Pa is 1030 nm.

[0032] The pulse generation unit 3 generates pulsed light PL from the initial pulsed light Pa. The pulsed light PL has a temporal waveform corresponding to the type of optical property to be measured. Further, the pulsed light PL may further have a number of pulses and a spectrum corresponding to the type of optical property to be measured. In the pulse generation unit 3, the temporal waveform of the pulsed light PL can be changed according to the type of optical property to be measured. Further, the pulse generation unit 3 may be able to further change the number of pulses and the spectrum of the pulsed light PL according to the type of optical property to be measured. Note that the spectrum of the pulsed light includes either the phase spectrum of the pulsed light, the intensity spectrum of the pulsed light, or both the phase spectrum and the intensity spectrum of the pulsed light.

[0033] FIG. 2 is a diagram showing a configuration example of the pulse generation unit 3. The pulse generation unit 3 includes a diffraction grating 12, a lens 13, a spatial light modulator (SLM) 14, a lens 15, and a diffraction grating 16. The diffraction grating 12 is a spectroscopic element and is optically coupled to the pulse laser light source 2. The SLM 14 is optically coupled to the diffraction grating 12 via the lens 13. The diffraction grating 12 spatially separates a plurality of wavelength components included in the initial pulsed light Pa for each wavelength. Note that, as the spectroscopic element, other optical components such as a prism may be used instead of the diffraction grating 12. The initial pulsed light Pa is incident obliquely on the diffraction grating 12 and is split into a plurality of wavelength components. The light Pb including the plurality of wavelength components is condensed for each wavelength component by the lens 13 and is imaged on the modulation surface of the SLM 14. The lens 13 may be a convex lens made of a light transmissive member, or may be a concave mirror having a concave light reflecting surface.

[0034] SLM14 imparts a phase shift for each wavelength to the initial pulse light Pa in order to convert the initial pulse light Pa into the pulse light PL. Specifically, SLM14 receives a control signal from the control unit 18 in order to impart a phase shift to the initial pulse light Pa and generate the pulse light PL. SLM14 presents a phase pattern by receiving the control signal output from the control unit 18. The control unit 18 can be constituted by, for example, a computer. SLM14 performs at least one of phase modulation and intensity modulation of the light Pb using the presented phase pattern. Also, SLM14 may simultaneously perform phase modulation and intensity modulation of the light Pb using the presented phase pattern. In this way, SLM14 mutually shifts the phases of the plurality of wavelength components output from the diffraction grating 12. SLM14 is, for example, a phase modulation type. In one embodiment, SLM14 is of the LCOS (Liquid crystal on silicon) type. Although a transmissive SLM14 is shown in the drawing, SLM14 may be a reflective type.

[0035] Figure 3 is a diagram showing the modulation surface 17 of SLM14. A plurality of modulation regions 17a are arranged along a certain direction AA on the modulation surface 17, and each modulation region 17a extends in a direction AB intersecting the direction AA. The direction AA is the spectral direction by the diffraction grating 12. This modulation surface 17 functions as a Fourier transform surface, and each corresponding wavelength component after spectroscopy is incident on each of the plurality of modulation regions 17a. SLM14 independently modulates the phase and intensity of each incident wavelength component in each modulation region 17a from other wavelength components. When SLM14 is a phase modulation type, the intensity modulation is realized by the phase pattern (phase image) presented on the modulation surface 17.

[0036] Each wavelength component of the modulated light Pc modulated by the SLM14 is collected at a single point on the diffraction grating 16 by the lens 15. At this time, the lens 15 functions as a condensing optical system for condensing the modulated light Pc. The lens 15 may be a convex lens made of an optical transmission member, or may be a concave mirror having a concave light reflecting surface. Further, the diffraction grating 16 functions as a multiplexing optical system and multiplexes each wavelength component after modulation. That is, by these lens 15 and diffraction grating 16, a plurality of wavelength components of the modulated light Pc are condensed and multiplexed with each other to become the pulsed light PL.

[0037] The control unit 18 stores in advance a plurality of phase patterns in order to generate the pulsed light PL having at least one of the number of pulses, the spectrum, and the time waveform according to the type of the optical characteristics to be measured. The control unit 18 selectively outputs these phase patterns to the SLM14.

[0038] Referring to FIG. 1 again. The measurement object B is disposed on the optical axis of the pulsed light PL output from the pulse forming unit 3. The pulsed light PL output from the pulse forming unit 3 is irradiated onto the measurement object B. From the measurement object B, the pulsed light PL that has passed through the measurement object B is output. Alternatively, the pulsed light PL reflected or scattered by the measurement object B may be output from the measurement object B. The time waveform of the pulsed light PL changes according to the optical characteristics of the measurement object B.

[0039] The optical system 4 is disposed on the optical path of the pulsed light PL output from the measurement object B. The optical system 4 has an optical attenuation unit 41. The attenuation rate of the optical attenuation unit 41 with respect to one wavelength component constituting the pulsed light PL is greater than the attenuation rate of the optical attenuation unit 41 with respect to another wavelength component constituting the pulsed light PL. In one example, the optical attenuation unit 41 has a wavelength filter. The wavelength filter includes the wavelength of one wavelength component constituting the pulsed light PL within a cutoff band and includes the wavelength of another wavelength component constituting the pulsed light PL within a transmission band. The wavelength filter may be any of a band-pass filter, a high-pass filter, and a low-pass filter. In the present embodiment, one wavelength component constituting the pulsed light PL is the pump light irradiated to the measurement object B when measuring the time response inside the measurement object B due to light irradiation. Another wavelength component constituting the pulsed light PL is the probe light irradiated to the measurement object B when measuring the time response inside the measurement object B due to light irradiation.

[0040] The optical system 4 is configured to be mutually switchable between a first state in which the optical attenuation unit 41 is disposed on the optical path of the pulsed light PL output from the measurement object B and a second state in which the optical attenuation unit 41 is not disposed on the optical path thereof. The optical system 4 is set to the first state when measuring the time response inside the measurement object B due to light irradiation, and is set to the second state when measuring the wavelength dispersion amount of the measurement object B.

[0041] FIGS. 4(a) and 4(b) are diagrams schematically showing an optical system 4A as an example of the optical system 4. In the optical system 4A, the optical attenuation unit 41 is supported by an actuator (not shown), so that it can move in a direction intersecting the optical axis of the pulsed light PL (for example, a direction perpendicular to the optical axis of the pulsed light PL) (arrow AC in the figure). The position of the actuator in this direction is controlled by, for example, the control unit 18. FIG. 4(a) shows the first state in which the optical attenuation unit 41 is disposed on the optical path of the pulsed light PL output from the measurement object B. FIG. 4(b) shows the second state in which the optical attenuation unit 41 is not disposed on the optical path of the pulsed light PL output from the measurement object B. In the second state, the pulsed light PL passes by the side of the optical attenuation unit 41.

[0042] FIG. 5(a) and FIG. 5(b) are diagrams schematically showing an optical system 4B as another example of the optical system 4. The optical system 4B has a configuration for switching between two optical paths for the pulsed light PL in addition to the light attenuation unit 41. The light attenuation unit 41 is disposed on one of the two optical paths. Specifically, the optical system 4B includes a pair of fixed mirrors 43a and 43b and a pair of movable mirrors 44a and 44b. The movable mirrors 44a and 44b are arranged side by side along the optical axis of the pulsed light PL when it enters the optical system 4B. The movable mirrors 44a and 44b are movable by being supported by an actuator (not shown) (arrows AD and AE in the figure). The fixed mirror 43a optically couples the movable mirror 44a and the light attenuation unit 41. The fixed mirror 43b optically couples the light attenuation unit 41 and the movable mirror 44b.

[0043] FIG. 5(a) shows a first state in which the light attenuation unit 41 is disposed on the optical path of the pulsed light PL output from the measurement object B. In the first state, the movable mirrors 44a and 44b are disposed on the optical axis of the pulsed light PL. The pulsed light PL is input to the optical system 4B, sequentially reflected by the movable mirror 44a and the fixed mirror 43a, reaches the light attenuation unit 41, passes through the light attenuation unit 41, and then is sequentially reflected by the fixed mirror 43b and the movable mirror 44b and output from the optical system 4B. Further, FIG. 5(b) shows a second state in which the light attenuation unit 41 is not disposed on the optical path of the pulsed light PL output from the measurement object B. In the second state, the movable mirrors 44a and 44b are not disposed on the optical axis of the pulsed light PL, and the pulsed light PL is output from the optical system 4B without hitting the movable mirrors 44a and 44b.

[0044] Note that in this example, the light attenuation unit 41 is disposed on one optical path including the fixed mirrors 43a and 43b, but the light attenuation unit 41 may be disposed on the optical path between the movable mirror 44a and the movable mirror 44b in the state shown in FIG. 5(a), that is, on the other optical path not including the fixed mirrors 43a and 43b. In that case, the positions of the movable mirrors 44a and 44b shown in FIG. 5(a) form the second state, and the positions of the movable mirrors 44a and 44b shown in FIG. 5(b) form the first state.

[0045] Figs. 6(a) and 6(b) schematically show an optical system 4C as yet another example of the optical system 4. The optical system 4C also has a configuration for switching between two optical paths for the pulsed light PL in addition to the light attenuation unit 41. The light attenuation unit 41 is disposed on one of the two optical paths. Specifically, the optical system 4C includes a pair of half mirrors 45a and 45b, a pair of fixed mirrors 46a and 46b, and a light absorber 47. The pulsed light PL input to the optical system 4C first reaches the half mirror 45a and is split by the half mirror 45a. One surface of the half mirror 45a is optically coupled to the light attenuation unit 41 by the fixed mirror 46a. The other surface of the half mirror 45a is optically coupled to one surface of the half mirror 45b. The other surface of the half mirror 45b is optically coupled to the light attenuation unit 41 by the fixed mirror 46b. The light absorber 47 is movable by being supported by an actuator (arrow AF in the figure) not shown.

[0046] FIG. 6(a) shows a first state in which the light attenuation unit 41 is disposed on the optical path of the pulsed light PL output from the measurement object B. In the first state, the light absorption material 47 is disposed on the optical path (the optical path that does not pass through the light attenuation unit 41) between the half mirror 45a and the half mirror 45b. At this time, a part of the pulsed light PL branched by the half mirror 45a is reflected by the fixed mirror 46a, reaches the light attenuation unit 41, passes through the light attenuation unit 41, and is then sequentially reflected by the fixed mirror 46b and the half mirror 45b, and is output from the optical system 4C. The remaining part of the pulsed light PL branched by the half mirror 45a enters the light absorption material 47 and disappears. FIG. 6(b) shows a second state in which the light attenuation unit 41 is not disposed on the optical path of the pulsed light PL output from the measurement object B. In the second state, the light absorption material 47 is disposed on either the optical path between the half mirror 45a and the light attenuation unit 41 or the optical path between the light attenuation unit 41 and the half mirror 45b. At this time, a part of the pulsed light PL branched by the half mirror 45a enters the light absorption material 47 and disappears. The remaining part of the pulsed light PL branched by the half mirror 45a passes through the optical path between the half mirror 45a and the half mirror 45b where the light attenuation unit 41 is not provided, and is output from the optical system 4C. In the optical system 4C, a light reflecting material or a light diffusing material may be used instead of the light absorption material 47.

[0047] Referring again to FIG. 1. The waveform measurement unit 5 measures the time waveform of the pulsed light PL that has passed through the optical system 4. The waveform measurement unit 5 of the present embodiment includes a correlation optical system 50 and a photodetector 51.

[0048] The correlation optical system 50 is optically coupled to the optical system 4 and receives the pulsed light PL that has passed through the optical system 4. The correlation optical system 50 converts the pulsed light PL into a correlation light including a cross-correlation or an auto-correlation. The pulsed light PL converted into the correlation light is output from the correlation optical system 50.

[0049] FIG. 7 is a diagram showing a configuration example of the correlation optical system 50. The correlation optical system 50 may be configured to include a lens 52a, an optical element 53, and a lens 52b. The lens 52a is provided on the optical path between the optical system 4 and the optical element 53, and condenses the pulsed light PL that has passed through the optical system 4 onto the optical element 53. The optical element 53 is a light emitter including at least one of, for example, a nonlinear optical crystal that generates second harmonic generation (SHG), and a phosphor. Examples of the nonlinear optical crystal include a KTP (KTiOPO4) crystal, an LBO (LiB3O5) crystal, a BBO (β-BaB2O4) crystal, and the like. Examples of the phosphor include coumarin, stilbene, rhodamine, and the like. The optical element 53 inputs the pulsed light PL and converts the pulsed light PL into correlation light including mutual correlation or autocorrelation. The lens 52b collimates or condenses the pulsed light PL that has been converted into correlation light and output from the optical element 53. Note that the pulsed light PL is converted into correlation light in order to more accurately detect the time waveform.

[0050] Here, a configuration example of the correlation optical system 50 will be described in detail. FIG. 8 is a diagram schematically showing a correlation optical system 50A for converting the incident pulsed light PL into correlation light including autocorrelation as a configuration example of the correlation optical system 50. The correlation optical system 50A has a beam splitter 54 as an optical branching component for bifurcating the pulsed light PL. The beam splitter 54 is optically coupled to the optical system 4, transmits a part of the pulsed light PL input from the optical system 4, and reflects the remaining part. The branching ratio of the beam splitter 54 is, for example, 1:1. One pulsed light PLu branched by the beam splitter 54 reaches the lens 52a through an optical path 50c including a plurality of mirrors 55. The other pulsed light PLv branched by the beam splitter 54 reaches the lens 52a through an optical path 50d including a plurality of mirrors 56. The optical length of the optical path 50c and the optical length of the optical path 50d are different from each other. Therefore, the plurality of mirrors 55 and the plurality of mirrors 56 constitute a delay optical system that gives a time difference to one pulsed light PLu and the other pulsed light PLv branched at the beam splitter 54. Further, at least a part of the plurality of mirrors 56 is mounted on a moving stage 57, and the optical length of the optical path 50d is variable. Therefore, in this configuration, the time difference between the pulsed light PLu and the pulsed light PLv can be made variable.

[0051] In this example, the optical element 53 includes a nonlinear optical crystal. The lens 52a condenses each of the pulsed lights PLu and PLv toward the optical element 53, and intersects the optical axes of the pulsed lights PLu and PLv with each other at a predetermined angle in the optical element 53. Thereby, in the optical element 53 which is a nonlinear optical crystal, a second harmonic wave is generated starting from the intersection point of the pulsed lights PLu and PLv. This second harmonic wave is correlation light and includes the autocorrelation of the pulsed light PL. The correlation light is parallelized or condensed by the lens 52b and then input to the photodetector 51.

[0052] FIG. 9 is a diagram schematically showing a correlation optical system 50B for converting a pulsed light PL into a correlation light including a cross-correlation, as another configuration example of the correlation optical system 50. In the correlation optical system 50B, the pulsed light PL reaches the lens 52a through the optical path 50e, and the reference pulsed light Pr reaches the lens 52a through the optical path 50f. The optical path 50f includes a plurality of mirrors 58 and is bent in a U shape. Further, at least a part of the plurality of mirrors 58 is mounted on a moving stage 59, and the optical length of the optical path 50f is variable. Therefore, in this configuration, the time difference (timing difference reaching the lens 52a) between the pulsed light PL and the reference pulsed light Pr can be made variable.

[0053] Also in this example, the optical element 53 includes a nonlinear optical crystal. The lens 52a condenses the pulsed light PL and the reference pulsed light Pr toward the optical element 53, and causes the optical axis of the pulsed light PL and the optical axis of the reference pulsed light Pr to intersect each other at a predetermined angle in the optical element 53. Thereby, in the optical element 53 which is a nonlinear optical crystal, a second harmonic wave is generated starting from the intersection point of the pulsed light PL and the reference pulsed light Pr. This second harmonic wave is a correlation light and includes the cross-correlation of the pulsed light PL. This correlation light is parallelized or condensed by the lens 52b and then input to the photodetector 51.

[0054] FIG. 10 is a diagram schematically showing a correlation optical system 50C for converting a pulsed light PL into a correlation light including a cross-correlation, as still another configuration example of the correlation optical system 50. In this example, the SLM14 of the pulse forming unit 3 is a polarization-dependent spatial light modulator having a modulation action in a first polarization direction. On the other hand, the polarization plane of the initial pulsed light Pa input to the pulse forming unit 3 is inclined with respect to the polarization direction in which the SLM14 has a modulation action, and the initial pulsed light Pa includes a polarization component in the first polarization direction (arrow Dp1 in the figure) and a polarization component in a second polarization direction orthogonal to the first polarization direction (symbol Dp2 in the figure). Further, the polarization state of the initial pulsed light Pa is not limited to the above polarization state (oblique linearly polarized light), and may be elliptically polarized light.

[0055] Of the initial pulsed light Pa, the polarization component in the first polarization direction is modulated by the SLM 14 and output from the pulse forming section 3 as the pulsed light PL. On the other hand, the polarization component in the second polarization direction of the initial pulsed light Pa is not modulated by the SLM 14 and is output as it is from the pulse forming section 3. This unmodulated polarization component is provided to the correlation optical system 50C coaxially with the pulsed light PL as the reference pulsed light Pr. The correlation optical system 50C generates correlation light including the mutual correlation of the pulsed light PL from the pulsed light PL and the reference pulsed light Pr. In this configuration example, by giving a delay to the pulsed light PL in the SLM 14 and making the delay time variable (arrow E in the figure), the time difference (timing difference reaching the lens 52a) between the pulsed light PL and the reference pulsed light Pr can be made variable, and correlation light including the mutual correlation of the pulsed light PL can be suitably generated in the correlation optical system 50C.

[0056] As shown in FIGS. 8 to 10, the correlation optical system 50 is an optical system that spatially and temporally superimposes the pulsed light PL on itself or another pulsed light. Specifically, by temporally sweeping one pulsed light, a correlation waveform conforming to the temporal waveform shape of the pulsed light PL is detected. Here, generally, the sweeping of the pulsed light is performed by spatially changing the optical path length using a driving stage or the like, so the movement amount of the stage corresponds to the time delay amount of the correlation waveform. At this time, the time delay amount with respect to the stage movement amount is extremely small. Therefore, by adopting the correlation optical system 50, the pulse shape is observed at a high time resolution scale reaching the femtosecond order in the photodetector 51, so the temporal waveform of the pulsed light PL is detected with higher accuracy.

[0057] Referring to FIG. 1 again. The photodetector 51 receives the pulsed light PL that has been converted into correlation light and output from the correlation optical system 50. The photodetector 51 detects the temporal waveform of this pulsed light PL. The photodetector 51 is configured to include a photodetector (photodetector) such as a photodiode, for example. The photodetector 51 detects the temporal waveform of the pulsed light PL by converting the intensity of the pulsed light PL into an electrical signal. The electrical signal that is the detection result is provided to the analysis unit 6.

[0058] The analysis unit 6 is electrically connected to the photodetector 51. The analysis unit 6 obtains the optical characteristics of the measurement object B based on the time waveform of the pulsed light PL converted into correlation light. FIG. 11 is a diagram schematically showing a configuration example of the hardware of the analysis unit 6 and the control unit 18. As shown in FIG. 11, the analysis unit 6 and the control unit 18 physically include a processor (CPU) 61, a main storage device such as a ROM 62 and a RAM 63, an input device 64 such as a keyboard, a mouse, and a touch screen, an output device 65 such as a display (including a touch screen), a communication module 66 such as a network card for transmitting and receiving data to and from other devices, and an auxiliary storage device 67 such as a hard disk, and can be configured as a normal computer.

[0059] The auxiliary storage device 67 of the control unit 18 stores a plurality of data regarding a plurality of phase modulation patterns for generating the pulsed light PL. The processor 61 reads out one of these data as needed and controls the phase modulation pattern presented to the SLM 14 based on the data.

[0060] In addition, the auxiliary storage device 67 of the analysis unit 6 stores a program for obtaining the optical characteristics of the measurement object B based on the time waveform of the pulsed light PL converted into correlation light. In other words, the program for obtaining the optical characteristics of the measurement object B operates the processor 61 of the computer as the analysis unit 6. The processor 61 obtains the optical characteristics of the measurement object B by executing this program. The storage device for storing the program for obtaining the optical characteristics of the measurement object B may be a non-transitory recording medium. Examples of the recording medium include recording media such as flexible disks, CDs, and DVDs, recording media such as ROMs, semiconductor memories, and cloud servers. The information regarding the obtained optical characteristics of the measurement object B is output to the output device 65 or output to an external device via the communication module 66.

[0061] The optical property measurement method of this embodiment will be described. FIG. 12 is a flowchart showing the optical property measurement method of this embodiment. This optical property measurement method is preferably implemented using, for example, the above-described optical property measurement apparatus 1A.

[0062] First, in the optical system 4, either a first state (a state in which the light attenuation unit 41 is arranged on the optical path of the pulsed light PL output from the measurement object B) or a second state (a state in which the light attenuation unit 41 is not arranged on the optical path of the pulsed light PL output from the measurement object B) is selected (step ST1). Next, using the pulse forming unit 3, the measurement object B is irradiated with a pulsed light PL having at least one of the number of pulses, spectrum, and time waveform corresponding to the type of optical property to be measured (step ST2). In step ST2, the pulsed light PL is generated using the SLM 14 that performs at least one of phase modulation and intensity modulation of the input initial pulsed light Pa. Also, in step ST2, the pulsed light PL may be generated using the SLM 14 that simultaneously performs phase modulation and intensity modulation of the input initial pulsed light Pa. The types of optical properties to be measured include the time response inside the measurement object B caused by light irradiation and the amount of wavelength dispersion of the measurement object B. In step ST1, the first state is selected during the measurement of the time response, and the second state is selected during the measurement of the amount of wavelength dispersion. Subsequently, the time waveform of the pulsed light PL output from the measurement object B and then passing through the optical system 4 is measured (step ST3). Steps ST2 and ST3 may be repeated as many times as necessary while changing at least one of the number of pulses, spectrum, and time waveform of the pulsed light PL according to the type of optical property to be measured (steps ST4, ST5). Thereafter, based on the measured time waveform, the optical property of the measurement object B is obtained (step ST6).

[0063] Here, the phase modulation for generating the pulsed light PL in the SLM 14 of the pulse forming unit 3 shown in FIG. 2 will be described in detail. The region in front of the lens 15 (spectral region) and the region behind the diffraction grating 16 (time region) are in a Fourier transform relationship with each other, and the phase modulation in the spectral region affects the temporal intensity waveform in the time region. Therefore, the output light from the pulse forming unit 3 can have various temporal intensity waveforms different from the initial pulsed light Pa according to the modulation pattern of the SLM 14.

[0064] FIG. 13 is a diagram showing the configuration of a modulation pattern calculation device 20 that calculates the modulation pattern of the SLM 14. The modulation pattern calculation device 20 is, for example, a personal computer; a smart device such as a smartphone or a tablet terminal; or a computer having a processor such as a cloud server. The control unit 18 shown in FIG. 2 may also serve as the modulation pattern calculation device 20. The modulation pattern calculation device 20 calculates a phase modulation pattern for approximating the temporal intensity waveform of the output light of the pulse forming unit 3 to a desired waveform, and provides the phase modulation pattern to the control unit 18. The modulation pattern is data for controlling the SLM 14, and is data including a table of the intensity of the complex amplitude distribution or the intensity of the phase distribution. The modulation pattern is, for example, a computer-generated hologram (CGH).

[0065] The modulation pattern calculation device 20 of this embodiment causes the control unit 18 to store a phase pattern including a phase pattern for phase modulation that gives a phase spectrum for obtaining a desired waveform to the output light and a phase pattern for intensity modulation that gives an intensity spectrum for obtaining a desired waveform to the output light. For this purpose, as shown in FIG. 13, the modulation pattern calculation device 20 includes an arbitrary waveform input unit 21, a phase spectrum design unit 22, an intensity spectrum design unit 23, and a modulation pattern generation unit 24. That is, the processor of the computer provided in the modulation pattern calculation device 20 realizes the functions of the arbitrary waveform input unit 21, the phase spectrum design unit 22, the intensity spectrum design unit 23, and the modulation pattern generation unit 24. Each function may be realized by the same processor or by different processors.

[0066] The processor of the computer can realize each of the above functions by a modulation pattern calculation program. Therefore, the modulation pattern calculation program causes the processor of the computer to operate as the arbitrary waveform input unit 21, the phase spectrum design unit 22, the intensity spectrum design unit 23, and the modulation pattern generation unit 24 in the modulation pattern calculation device 20. The modulation pattern calculation program is stored in a storage device (storage medium) inside or outside the computer. The storage device may be a non-temporary recording medium. Examples of the recording medium include recording media such as flexible disks, CDs, and DVDs, recording media such as ROMs, semiconductor memories, cloud servers, and the like.

[0067] The arbitrary waveform input unit 21 receives the input of a desired time-intensity waveform from the operator. The operator inputs information regarding the desired number of pulses, spectrum, and time waveform of the pulsed light PL (hereinafter referred to as the desired number of pulses, etc.) to the arbitrary waveform input unit 21. The desired number of pulses, etc. is determined by the operator according to the type of optical property to be measured. The information regarding the desired number of pulses, etc. is provided from the arbitrary waveform input unit 21 to the phase spectrum design unit 22 and the intensity spectrum design unit 23. The phase spectrum design unit 22 calculates the phase spectrum of the output light of the pulse formation unit 3 suitable for realizing the given desired number of pulses, etc. The intensity spectrum design unit 23 calculates the intensity spectrum of the output light of the pulse formation unit 3 suitable for realizing the given desired number of pulses, etc. The modulation pattern generation unit 24 calculates a phase modulation pattern (e.g., a computer-generated hologram) for applying the phase spectrum obtained by the phase spectrum design unit 22 and the intensity spectrum obtained by the intensity spectrum design unit 23 to the output light of the pulse formation unit 3.

[0068] FIG. 14 is a block diagram showing the internal configuration of the phase spectrum design unit 22 and the intensity spectrum design unit 23. As shown in FIG. 14, the phase spectrum design unit 22 and the intensity spectrum design unit 23 include a Fourier transform unit 25, a function substitution unit 26, a waveform function correction unit 27, an inverse Fourier transform unit 28, and a target generation unit 29. The target generation unit 29 includes a Fourier transform unit 29a and a spectrogram correction unit 29b. The functions of these respective components will be described in detail later.

[0069] Here, the desired time-intensity waveform is represented as a function in the time domain, and the phase spectrum is represented as a function in the frequency domain. Therefore, the phase spectrum corresponding to the desired time-intensity waveform can be obtained, for example, by an iterative Fourier transform based on the desired time-intensity waveform. FIG. 15 is a diagram showing the calculation procedure of the phase spectrum by the iterative Fourier transform method. First, an initial intensity spectrum function A0(ω) and a phase spectrum function Ψ0(ω) that are functions of frequency ω are prepared (processing number (1) in the figure). In one example, these intensity spectrum function A0(ω) and phase spectrum function Ψ0(ω) represent the spectral intensity and spectral phase of the input light, respectively. Next, a waveform function (a) in the frequency domain including the intensity spectrum function A0(ω) and the phase spectrum function Ψ n (ω) is prepared (processing number (2) in the figure). [Number] The subscript n represents after the n-th Fourier transform process. Before the first (the first time) Fourier transform process, the initial phase spectrum function Ψ n (ω) described above is used as the phase spectrum function Ψ0(ω). i is an imaginary number.

[0070] Subsequently, a Fourier transform from the frequency domain to the time domain is performed on the above function (a) (arrow A1 in the figure). As a result, a waveform function (b) in the time domain including a time-intensity waveform function b n (t) and a time-phase waveform function Θ n (t) is obtained (processing number (3) in the figure). [Number] Subsequently, the time-intensity waveform function b n (t) included in the above function (b) is replaced with a time-intensity waveform function Target0(t) based on the desired waveform (processing numbers (4) and (5) in the figure). [Number] [Mathematics] Subsequently, an inverse Fourier transform from the time domain to the frequency domain is performed on the above function (d) (arrow A2 in the figure). As a result, a waveform function (e) in the frequency domain including the intensity spectrum function B n (ω) and the phase spectrum function Ψ n (ω) is obtained (processing number (6) in the figure). [Mathematics]

[0071] Subsequently, in order to constrain the intensity spectrum function B n (ω) included in the above function (e), it is replaced with the initial intensity spectrum function A0(ω) (processing number (7) in the figure). [Mathematics] Thereafter, by repeatedly performing the above processes (2) to (7) a plurality of times, the phase spectrum shape represented by the phase spectrum function Ψ n (ω) in the waveform function can be made closer to the phase spectrum shape corresponding to the desired time-intensity waveform. The finally obtained phase spectrum function Ψ IFTA (ω) serves as the basis for the modulation pattern to obtain the desired time-intensity waveform.

[0072] However, in the iterative Fourier method as described above, although the time-intensity waveform can be controlled, there is a problem that the frequency components (spectrum) that make up the time-intensity waveform cannot be controlled. Therefore, the modulation pattern calculation device 20 of the present embodiment calculates a phase spectrum function and an intensity spectrum function that form the basis of the modulation pattern using the calculation method described below. FIG. 16 is a diagram showing the calculation procedure of the phase spectrum function in the phase spectrum design unit 22. First, an initial intensity spectrum function A0(ω) and a phase spectrum function Φ0(ω) that are functions of the frequency ω are prepared (processing number (11) in the figure). In one example, these intensity spectrum function A0(ω) and phase spectrum function Φ0(ω) represent the spectral intensity and spectral phase of the input light, respectively. Next, a first waveform function (g) in the frequency domain including the intensity spectrum function A0(ω) and the phase spectrum function Φ0(ω) is prepared (processing number (12)). However, i is an imaginary number.

Number

[0073] Subsequently, the Fourier transform unit 25 of the phase spectrum design unit 22 performs a Fourier transform on the above function (g) from the frequency domain to the time domain (arrow A3 in the figure). As a result, a second waveform function (h) in the time domain including the time-intensity waveform function a0(t) and the time-phase waveform function φ0(t) is obtained (processing number (13) in the figure).

Number

[0074] Subsequently, the function replacement unit 26 of the phase spectrum design unit 22 substitutes the time-intensity waveform function Target0(t) based on the desired waveform input in the arbitrary waveform input unit 21 into the time-intensity waveform function b0(t) as shown in the following mathematical formula (i) (processing number (14) in the figure).

Number

[0075] Subsequently, the function replacement unit 26 of the phase spectrum design unit 22 replaces the time-intensity waveform function a0(t) with the time-intensity waveform function b0(t) as shown in the following mathematical formula (j). That is, the time-intensity waveform function a0(t) included in the above function (h) is replaced with the time-intensity waveform function Target0(t) based on a desired waveform (processing number (15) in the figure). [Number]

[0076] Subsequently, the waveform function correction unit 27 of the phase spectrum design unit 22 corrects the second waveform function so that the spectrogram of the replaced second waveform function (j) approaches the target spectrogram generated in advance according to a desired wavelength band. First, the second waveform function (j) after replacement is subjected to time-frequency conversion to convert the second waveform function (j) into a spectrogram SG 0,k (ω,t) (processing number (15a) in the figure). The subscript k represents the k-th conversion process.

[0077] Here, time-frequency conversion means performing frequency filter processing or numerical operation processing (processing of multiplying while shifting a window function to derive a spectrum for each time) on a composite signal such as a time waveform, and converting it into three-dimensional information consisting of time, frequency, and the strength of the signal component (spectrum intensity). In this embodiment, the conversion result (time, frequency, spectrum intensity) is defined as a "spectrogram".

[0078] Examples of time-frequency conversion include the Short-Time Fourier Transform (STFT) and wavelet transforms (Haar wavelet transform, Gabor wavelet transform, Mexican hat wavelet transform, Morlet wavelet transform).

[0079] Read out the target spectrogram TargetSG0(ω,t) pre-generated according to the desired wavelength band from the target generation unit 29. This target spectrogram TargetSG0(ω,t) is approximately equivalent to the target time waveform (time intensity waveform and the frequency components constituting it), and is generated in the target spectrogram function of the process number (15b).

[0080] Next, the waveform function correction unit 27 of the phase spectrum design unit 22 performs pattern matching between the spectrogram SG 0,k (ω,t) and the target spectrogram TargetSG0(ω,t), and examines the similarity (to what extent they match). In this embodiment, an evaluation value is calculated as an index representing the similarity. Then, in the subsequent process number (15c), it is determined whether the obtained evaluation value satisfies a predetermined end condition. If the condition is satisfied, proceed to process number (16); if not, proceed to process number (15d). In process number (15d), the time phase waveform function φ0(t) included in the second waveform function is changed to an arbitrary time phase waveform function φ 0,k (t). The second waveform function after changing the time phase waveform function is converted back to a spectrogram by time-frequency conversion such as STFT. Thereafter, the above-described process numbers (15a) to (15d) are repeatedly performed. In this way, the second waveform function is corrected so that the spectrogram SG 0,k (ω,t) gradually approaches the target spectrogram TargetSG0(ω,t).

[0081] Thereafter, the inverse Fourier transform unit 28 of the phase spectrum design unit 22 performs an inverse Fourier transform on the corrected second waveform function (arrow A4 in the figure) to generate a third waveform function (k) in the frequency domain (process number (16)).

Number

[0082] FIG. 17 is a diagram showing the calculation procedure of the intensity spectrum function in the intensity spectrum design unit 23. Since the processing numbers from (11) to (15c) are the same as the calculation procedure of the spectral phase in the above-described phase spectrum design unit 22, the description thereof is omitted. The waveform function correction unit 27 of the intensity spectrum design unit 23 is the spectrogram SG 0,k When the evaluation value indicating the similarity between (ω,t) and the target spectrogram TargetSG0(ω,t) does not satisfy a predetermined end condition, the time intensity waveform function b0(t) is changed to an arbitrary time intensity waveform function b 0,k (t) while restraining the time phase waveform function φ0(t) included in the second waveform function to the initial value (processing number (15e)). The second waveform function after changing the time intensity waveform function is converted again into a spectrogram by time-frequency conversion such as STFT. Thereafter, the processing numbers (15a) to (15c) and (15e) are repeatedly performed. In this way, the second waveform function is corrected so that the spectrogram SG 0,k (ω,t) gradually approaches the target spectrogram TargetSG0(ω,t).

[0083] Thereafter, the inverse Fourier transform unit 28 of the intensity spectrum design unit 23 performs an inverse Fourier transform on the corrected second waveform function (arrow A4 in the figure) to generate a third waveform function (m) in the frequency domain (processing number (16)). [Number]

[0084] Subsequently, in the processing number (17), the filter processing unit of the intensity spectrum design unit 23 performs filter processing on the intensity spectrum function B 0,k (ω) included in the third waveform function (m) based on the intensity spectrum of the input light. Specifically, the intensity spectrum function B 0,kOf the intensity spectrum multiplied by the coefficient α with respect to (ω), the portion exceeding the cut-off intensity for each wavelength determined based on the intensity spectrum of the input light is cut off. In all wavelength ranges, the intensity spectrum function αB 0,k (ω) is made not to exceed the spectral intensity of the input light. In one example, the cut-off intensity for each wavelength is set to match the intensity spectrum of the input light (the initial intensity spectrum function A0(ω) in this embodiment). In that case, as shown in the following equation (n), the intensity spectrum function αB 0,k (ω), at frequencies higher than the intensity spectrum function A0(ω), the value of the intensity spectrum function A TWC-TFD (ω) takes the value of the intensity spectrum function A0(ω). At frequencies where the intensity spectrum function αB 0,k (ω) is less than or equal to the intensity spectrum function A0(ω), the value of the intensity spectrum function A TWC-TFD (ω) takes the value of the intensity spectrum function αB 0,k (ω) (processing number (17) in the figure). [Number] This intensity spectrum function A TWC-TFD (ω) is provided to the modulation pattern generation unit 24 as the finally obtained desired spectral intensity.

[0085] The modulation pattern generation unit 24 calculates a phase modulation pattern (for example, a computer-generated hologram) for applying the spectral phase indicated by the phase spectrum function Φ TWC-TFD (ω) calculated in the phase spectrum design unit 22 and the spectral intensity indicated by the intensity spectrum function A TWC-TFD (ω) calculated in the intensity spectrum design unit 23 to the output light.

[0086] FIG. 18 is a diagram showing an example of a generation procedure of a target spectrogram TargetSG0(ω, t) in the target generation unit 29. The target spectrogram TargetSG0(ω, t) shows a target time waveform. The time waveform is a time intensity waveform and the frequency components (wavelength band components) that constitute it. Therefore, the creation of the target spectrogram is a very important process for controlling the frequency components (wavelength band components). As shown in FIG. 21, the target generation unit 29 first inputs a spectral waveform (an initial intensity spectral function A0(ω) and an initial phase spectral function Φ0(ω)), and a desired time intensity waveform function Target0(t). In addition, the target generation unit 29 inputs a time function p0(t) including desired frequency (wavelength) band information (processing number (21)).

[0087] Next, the target generation unit 29 calculates a phase spectral function Φ IFTA (ω) for realizing the time intensity waveform function Target0(t) using, for example, the iterative Fourier transform method shown in FIG. 15 (processing number (22)).

[0088] Subsequently, the target generation unit 29 calculates an intensity spectral function A IFTA (ω) for realizing the time intensity waveform function Target0(t) by the iterative Fourier transform method using the phase spectral function Φ IFTA (ω) obtained above (processing number (23)). FIG. 19 is a diagram showing an example of a procedure for calculating the intensity spectral function A IFTA (ω).

[0089] Referring to FIG. 19, first, an initial intensity spectral function A k=0 (ω) and a phase spectral function Ψ0(ω) are prepared (processing number (31) in the figure). Next, a waveform function (o) in the frequency domain including the intensity spectral function A k (ω) and the phase spectral function Ψ0(ω) is prepared (processing number (32) in the figure).

Equation

[0090] Subsequently, a Fourier transform from the frequency domain to the time domain is performed on the above function (o) (arrow A5 in the figure). As a result, a waveform function (p) in the frequency domain including the time intensity waveform function b k (t) is obtained (processing number (33) in the figure).

Number

[0091] Subsequently, the time intensity waveform function b k (t) included in the above function (p) is replaced with the time intensity waveform function Target0(t) based on the desired waveform (processing numbers (34) and (35) in the figure).

Number

Number

[0092] Subsequently, an inverse Fourier transform from the time domain to the frequency domain is performed on the above function (r) (arrow A6 in the figure). As a result, a waveform function (s) in the frequency domain including the intensity spectrum function C k (ω) and the phase spectrum function Ψ k (ω) is obtained (processing number (36) in the figure).

Number

[0093] In addition, for the intensity spectrum function C k (ω) in the frequency domain after the inverse Fourier transform, filtering is performed based on the intensity spectrum of the input light. Specifically, among the intensity spectra represented by the intensity spectrum function C k (ω), the part exceeding the cut-off intensity for each wavelength determined based on the intensity spectrum of the input light is cut. In one example, the cut-off intensity for each wavelength is set to match the intensity spectrum of the input light (for example, the initial intensity spectrum function A k=0 (ω)). In that case, as shown in the following mathematical formula (u), when the intensity spectrum function C k (ω) is at a frequency higher than the intensity spectrum function A k=0 (ω), the value of the intensity spectrum function A k (ω) is incorporated as the value of the intensity spectrum function A k=0 (ω). When the intensity spectrum function C k (ω) is equal to or less than the intensity spectrum function A k=0 (ω), the value of the intensity spectrum function C k (ω) is incorporated as the value of the intensity spectrum function A k (ω) (processing number (37b) in the figure). [Number] Replace the intensity spectrum function C k (ω) included in the above function (s) with the intensity spectrum function A k (ω) after the filtering process according to the above mathematical formula (u).

[0094] Thereafter, by repeatedly performing the above processes (32) to (37b), the intensity spectrum shape represented by the intensity spectrum function A k (ω) in the waveform function can be made to approach the intensity spectrum shape corresponding to the desired time intensity waveform. Finally, the intensity spectrum function A IFTA (ω) is obtained.

[0095] Referring to FIG. 18 again. The phase spectrum function Φ IFTA (ω) and the intensity spectrum function A IFTA (ω) are calculated, and a third waveform function (v) in the frequency domain including these functions is obtained (processing number (24)). [Number] The Fourier transform unit 29a of the target generation unit 29 Fourier-transforms the above waveform function (v). Thereby, a fourth waveform function (w) in the time domain is obtained (processing number (25)). [Number]

[0096] The spectrogram correction unit 29b of the target generation unit 29 converts the fourth waveform function (w) into a spectrogram SG IFTA (ω,t) by time-frequency conversion (processing number (26)). Then, in processing number (27), based on the time function p0(t) including the desired frequency (wavelength) band information, the spectrogram SG IFTA (ω,t) is corrected to generate a target spectrogram TargetSG0(ω,t). For example, a characteristic pattern appearing in the spectrogram SG IFTA (ω,t) composed of two-dimensional data is partially cut out, and the frequency components of the part are operated based on the time function p0(t). Hereinafter, specific examples thereof will be described in detail.

[0097] For example, consider the case where a triple pulse with a time interval of 2 picoseconds is set as the desired time intensity waveform function Target0(t). At this time, the spectrogram SG IFTA(ω, t) results in the outcome as shown in Fig. 20(a). In Fig. 20(a), the horizontal axis represents time (unit: femtosecond), and the vertical axis represents wavelength (unit: nm). The value of the spectrogram is indicated by the brightness and darkness in the figure, and the brighter the value of the spectrogram is larger. This spectrogram SG IFTA In (ω, t), the triple pulse appears as domains D1, D2, and D3 separated on the time axis at 2 picosecond intervals. The central (peak) wavelengths of domains D1, D2, and D3 are 800 nm.

[0098] If it is desired to control only the temporal intensity waveform of the output light (simply obtain a triple pulse), it is not necessary to operate these domains D1, D2, and D3. However, if it is desired to control the frequency (wavelength) band of each pulse, the operation of these domains D1, D2, and D3 becomes necessary. That is, as shown in Fig. 20(b), moving each of the domains D1, D2, and D3 independently along the direction along the wavelength axis (vertical axis) means changing the constituent frequency (wavelength band) of each pulse. Such a change in the constituent frequency (wavelength band) of each pulse is performed based on the time function p0(t).

[0099] For example, when describing the time function p0(t) such that the peak wavelength of domain D2 is fixed at 800 nm and the peak wavelengths of domains D1 and D3 are each translated by -2 nm and +2 nm, respectively, the spectrogram SG IFTA (ω, t) changes to the target spectrogram TargetSG0(ω, t) shown in Fig. 20(b). For example, by performing such processing on the spectrogram, it is possible to create a target spectrogram in which the constituent frequency (wavelength band) of each pulse is arbitrarily controlled without changing the shape of the temporal intensity waveform. [Time Response Measurement]

[0100] The time response measurement of the object to be measured B using the optical property measurement device 1A of this embodiment will be described. FIG. 21 is a diagram showing the operation of the optical property measurement device 1A when used as a time response measurement device. In the time response measurement, the optical system 4 is set to the first state, that is, a state in which the light attenuation unit 41 is arranged on the optical path of the pulsed light PL output from the object to be measured B. Then, the pulse forming unit 3 generates the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 as the pulsed light PL on the common optical axis reaching the object to be measured B from the initial pulsed light Pa. The pulse forming unit 3 can output these first pulsed light PL1, second pulsed light PL2, and third pulsed light PL3 individually at arbitrary timings with a time interval between them. The output order of the first pulsed light PL1, second pulsed light PL2, and third pulsed light PL3 is also arbitrary. In one example, the third pulsed light PL3 is output after the first pulsed light PL1 and the second pulsed light PL2 are output.

[0101] The (a) part of FIG. 22 schematically shows the time waveform of the first pulsed light PL1. The wavelength band of the first pulsed light PL1 includes the wavelength of the pump light. The wavelength of the pump light is included in a plurality of wavelength components constituting the initial pulsed light Pa. The wavelength of the pump light is, for example, in the range of 770 nm to 820 nm. The first pulsed light PL1 may consist only of light having the wavelength of the pump light. The time waveform of the first pulsed light PL1 is, for example, in the shape of a Gaussian function.

[0102] Part (b) of FIG. 22 schematically shows the time waveform of the second pulse light PL2. The wavelength band of the second pulse light PL2 includes the wavelength of the probe light. The wavelength of the probe light is included in the wavelength components of the initial pulse light Pa that are longer than the wavelength of the pump light among the plurality of wavelength components included in the initial pulse light Pa. Also, the wavelength of the probe light is included in the wavelength components on the long-wavelength side among the plurality of wavelength components included in the initial pulse light Pa. The wavelength of the probe light is, for example, in the range of 820 nm to 840 nm. The second pulse light PL2 may consist only of light having the wavelength of the probe light. A part of the wavelength band of the second pulse light PL2 may overlap with a part of the wavelength band of the first pulse light PL1. The time waveform of the second pulse light PL2 is, for example, in the shape of a Gaussian function. The peak intensity T2 of the second pulse light PL2 is smaller than the peak intensity T1 of the first pulse light PL1. For example, the peak intensity T2 of the second pulse light PL2 is 1 / 10 or less of the peak intensity T1 of the first pulse light PL1. Also, the pulse width W2, which is the full width at half maximum of the second pulse light PL2, is larger than the pulse width W1, which is the full width at half maximum of the first pulse light PL1. For example, the pulse width W2 of the second pulse light PL2 is 1 times or more and 100 times or less of the pulse width W1 of the first pulse light PL1.

[0103] FIG. 23 is a diagram for explaining the time waveform and the spectral waveform of the third pulse light PL3. Part (a) of FIG. 23 is a spectrogram, showing time on the horizontal axis, wavelength on the vertical axis, and representing the light intensity by the shade of color. Part (b) of FIG. 23 shows the time waveforms of the component pulses P3 and P4 included in the third pulse light PL3. Part (c) of FIG. 23 shows the spectral waveform obtained by synthesizing the component pulses P3 and P4, that is, the spectral waveform of the third pulse light PL3.

[0104] The spectrum of the third pulse light PL3 includes both the wavelength of the pump light and the wavelength of the probe light. The wavelength component of the pump light included in the third pulse light PL3 forms the component pulse P3. In one example, the peak intensity T3, pulse width W3, and wavelength component of the component pulse P3 are the same as the peak intensity T1, pulse width W1, and wavelength component of the first pulse light PL1, respectively. The wavelength component of the probe light included in the third pulse light PL3 forms the component pulse P4. In one example, the peak intensity T4, pulse width W4, and wavelength component of the component pulse P4 are the same as the peak intensity T2, pulse width W2, and wavelength component of the second pulse light PL2, respectively. The pulse width W3 of the wavelength component of the pump light included in the third pulse light PL3, that is, the component pulse P3, is smaller than the pulse width W4 of the wavelength component of the probe light included in the third pulse light PL3, that is, the component pulse P4. The third pulse light PL3 is obtained by superimposing the component pulse P4 on the component pulse P3. Preferably, the third pulse light PL3 does not include other components except the component pulse P3 and the component pulse P4.

[0105] As shown in part (c) of FIG. 23, the spectrum obtained by synthesizing the component pulses P3 and P4 has a single peak. However, referring to part (a) of FIG. 23, the central wavelengths of the component pulses P3 and P4 are shifted from each other. The single peak shown in part (c) of FIG. 23 substantially corresponds to the spectrum of the initial pulse light Pa. The peak wavelength interval between the component pulses P3 and P4 is determined by the spectral bandwidth of the initial pulse light Pa. In one example, it is within a range approximately twice the full width at half maximum of the spectral bandwidth of the initial pulse light Pa.

[0106] In the pulse forming unit 3, the time interval D1 between the intensity peak of the component (component pulse P3) of the wavelength of the pump light included in the third pulse light PL3 and the intensity peak of the component (component pulse P4) of the wavelength of the probe light is variable. This time interval can be appropriately changed according to the type or characteristics of the measurement object B. The time interval D1 may be zero. Also, in the pulse forming unit 3, the ratio (W3 / W4) between the pulse width W3 of the component (component pulse P3) of the wavelength of the pump light included in the third pulse light PL3 and the pulse width W4 of the component (component pulse P4) of the wavelength of the probe light is variable. This ratio (W3 / W4) can be appropriately changed according to the type or characteristics of the measurement object B. In this case, the ratio (W1 / W2) between the pulse width W1 of the first pulse light PL1 and the pulse width W2 of the second pulse light PL2 is also changed in accordance with the ratio (W3 / W4).

[0107] The control unit 18 (see FIG. 2) stores in advance a first phase pattern for generating the first pulse light PL1, a second phase pattern for generating the second pulse light PL2, and a third phase pattern for generating the third pulse light PL3. The control unit 18 selectively outputs the first phase pattern, the second phase pattern, or the third phase pattern to the SLM 14.

[0108] FIG. 24 schematically shows an example of the spectral waveform (spectral phase G11 and spectral intensity G12) given to the initial pulse light Pa by the third phase pattern. In FIG. 24, the horizontal axis represents the wavelength, and the vertical axis represents the respective values of the spectral intensity and the spectral phase. However, FIG. 24 is an example when the wavelength of the probe light is larger than the wavelength of the pump light. In the spectral waveform shown in FIG. 24, the wavelength characteristic of the spectral phase G11 includes a portion G11a that is constant in a band smaller than a certain wavelength λ A and a portion G11b that is a downwardly convex curve in a band larger than the wavelength λ A . The portion G11b is represented by the following equation using the phase φ(λ). φ(λ)=φ2(ω(λ)-ω B ) 2 / 2 However, φ2 is a constant. ω(λ) and ωB is the angular frequency, ω(λ) = 2πc / λ, ω B = 2πc / λ B (where c is the speed of light). The wavelength λ at which the partial G11b becomes the minimum value B is larger than the wavelength λ A . Also, the wavelength λ A is larger than the peak wavelength λ C of the spectral intensity. The partial G11a forms a component pulse P3 that is a component of the wavelength of the pump light among the third pulse light PL3, and the partial G11b forms a component pulse P4 that is a component of the wavelength of the probe light among the third pulse light PL3. Thus, at the spectral phase G11, the boundary between the part that forms the component pulse P3 and the part that forms the component pulse P4 becomes discontinuous.

[0109] The measurement object B is arranged on the optical axes of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 output from the pulse forming unit 3. The first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 output from the pulse forming unit 3 are irradiated onto the measurement object B. From the measurement object B, the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have passed through the measurement object B are output. Alternatively, the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 reflected or scattered by the measurement object B may be output from the measurement object B. The measurement object B is activated by the pump light, and its optical characteristics change. Therefore, compared with the time waveform of the probe light when the pump light is not irradiated simultaneously, that is, the time waveform of the second pulse light PL2, the time waveform of the probe light when the pump light is irradiated simultaneously, that is, the time waveform of the component pulse P4 of the third pulse light PL3, changes greatly immediately after the irradiation of the component pulse P3.

[0110] The (a) part of FIG. 25 is a graph schematically showing an example of the time waveform of the probe light that has passed through the measurement object B when the pump light is not irradiated on the measurement object B. The (b) part of FIG. 25 is a graph schematically showing an example of the time waveform of the probe light that has passed through the measurement object B when the pump light is irradiated on the measurement object B at time t0. Note that in the (b) part of FIG. 25, the graph shown in the (a) part of FIG. 25 is indicated by a dashed-dotted line. In this example, when the optical characteristics of the measurement object B change at the time t0 when the pump light is irradiated, the light transmittance of the measurement object B with respect to the wavelength of the probe light rapidly decreases. Thereafter, the light transmittance of the measurement object B returns to its original value over time. By subtracting the time waveform shown in the (a) part of FIG. 7 from the time waveform shown in the (b) part of FIG. 25, as shown in the (c) part of FIG. 25, the time response of the measurement object B to the irradiation of the pump light can be obtained.

[0111] The light attenuation unit 41 allows the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 output from the measurement object B to pass through. At this time, the light attenuation unit 41 allows the components of the wavelength of the probe light included in the second pulse light PL2 and the third pulse light PL3, typically the second pulse light PL2 and the component pulse P4, to pass through with almost no attenuation. Then, the light attenuation unit 41 attenuates the components of the wavelength of the pump light included in the first pulse light PL1 and the third pulse light PL3, typically the first pulse light PL1 and the component pulse P3. In other words, the attenuation rate of the light attenuation unit 41 with respect to the wavelength of the pump light is greater than the attenuation rate of the light attenuation unit 41 with respect to the wavelength of the probe light. When the light attenuation unit 41 has a wavelength filter, the wavelength filter includes the wavelength of the pump light within the blocking band and includes the wavelength of the probe light within the transmission band. The transmittance of the wavelength filter with respect to the wavelength of the pump light is, for example, in the range of 0% to 50%. The transmittance of the wavelength filter with respect to the wavelength of the probe light is, for example, in the range of 50% to 99%.

[0112] FIG. 26 is a graph showing an example of superimposing a first time waveform TW1 which is a time waveform of the first pulse light PL1 that has passed through the light attenuation unit 41, a second time waveform TW2 which is a time waveform of the second pulse light PL2 that has passed through the light attenuation unit 41, and a third time waveform TW3 which is a time waveform of the third pulse light PL3 that has passed through the light attenuation unit 41. In FIG. 26, the horizontal axis represents time (picoseconds (ps)), and the vertical axis represents light intensity (arbitrary unit). The first time waveform TW1 includes only the time waveform of the pump light attenuated by the light attenuation unit 41. The third time waveform TW3 includes a waveform obtained by superimposing the time waveform of the pump light attenuated by the light attenuation unit 41 and the time waveform of the probe light when the pump light is irradiated. Therefore, by performing correction processing such as calculating the difference between the third time waveform TW3 and the first time waveform TW1, it is possible to obtain the time waveform of the probe light when the pump light is irradiated while eliminating the influence of the pump light. Further, the second time waveform TW2 includes only the time waveform of the probe light when the pump light is not irradiated. Therefore, by comparing the difference between the third time waveform TW3 and the first time waveform TW1 with the second time waveform TW2, it is possible to compare the time waveform of the probe light when the pump light is irradiated with the time waveform of the probe light when the pump light is not irradiated, and obtain the time response inside the measurement object B. The evaluation of the time response inside the measurement object B based on the above principle is performed by an analysis unit 6 described later.

[0113] For the comparison between the difference between the third time waveform TW3 and the first time waveform TW1 and the second time waveform TW2, various methods can be used, such as evaluating the difference between these or evaluating the ratio between these. Also, the order of the above operations based on the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3 is arbitrary. FIG. 27 is a graph showing a time waveform TW4 which is a time waveform obtained by subtracting the second time waveform TW2 from the first time waveform TW1 and the third time waveform TW3, and a time waveform TW5 which is a time waveform obtained by subtracting the first time waveform TW1 from the time waveform TW4. In FIG. 27, the horizontal axis represents time (ps), and the vertical axis represents light intensity (arbitrary unit). For example, as shown in FIG. 27, first, the difference between the third time waveform TW3 and the second time waveform TW2 may be calculated, and then the difference between the obtained difference and the first time waveform TW1 may be calculated.

[0114] The correlation optical system 50 receives the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have passed through the light attenuation unit 41. The correlation optical system 50 converts the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 into correlation light including cross-correlation or auto-correlation. The first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 converted into correlation light are output from the correlation optical system 50 and detected by the photodetector 51.

[0115] The auxiliary storage device 67 (see FIG. 11) of the analysis unit 6 stores a program for obtaining the time response of the measurement object B based on the time waveforms of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 respectively converted into correlation light. The analysis unit 6 obtains the time response of the measurement object B based on the time waveforms of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 respectively converted into correlation light. The time waveforms of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 respectively converted into correlation light have correlations with the first time waveform TW1 which is the time waveform of the first pulse light PL1 that has passed through the light attenuation unit 41, the second time waveform TW2 which is the time waveform of the second pulse light PL2 that has passed through the light attenuation unit 41, and the third time waveform TW3 which is the time waveform of the third pulse light PL3 that has passed through the light attenuation unit 41 respectively. Therefore, the above-described principle of obtaining the time response inside the measurement object B based on the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3 can be directly applied even when the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are converted into correlation light.

[0116] Here, the time response measurement method of the present embodiment will be described. FIG. 28 is a flowchart showing the time response measurement method of the present embodiment. This time response measurement method is a method for measuring the time response inside the measurement object B caused by light irradiation, and is preferably implemented using, for example, the above-described optical property measurement device 1A.

[0117] First, in the optical system 4, a first state (a state in which the light attenuation unit 41 is disposed on the optical path of the pulsed light PL output from the measurement object B) is selected (step ST11). This step ST11 corresponds to step ST1 shown in FIG. 12. Next, steps ST2 and ST3 shown in FIG. 12 are repeated. Specifically, as step ST12, the first pulsed light PL1 is irradiated onto the measurement object B along a predetermined optical axis, and the first time waveform TW1, which is the time waveform of the first pulsed light PL1 that has passed through the light attenuation unit 41 after being output from the measurement object B, is measured. Next, as step ST13, the second pulsed light PL2 is irradiated onto the measurement object B along the above-mentioned predetermined optical axis, and the second time waveform TW2, which is the time waveform of the second pulsed light PL2 that has passed through the light attenuation unit 41 after being output from the measurement object B, is measured. Subsequently, as step ST14, the third pulsed light PL3 is irradiated onto the measurement object B along the above-mentioned predetermined optical axis, and the third time waveform TW3, which is the time waveform of the third pulsed light PL3 that has passed through the light attenuation unit 41 after being output from the measurement object B, is measured. In steps ST12 to ST14, as the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3, the time waveforms of the respective correlation lights of the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 may be measured.

[0118] The order of these steps ST12 to ST14 is arbitrary, and step ST13 may be performed first, or step ST14 may be performed first. However, the light intensity of the third pulsed light PL3 is greater than the light intensities of the first pulsed light PL1 and the second pulsed light PL2. Depending on the measurement object B, irreversible characteristic changes may occur when irradiated with light having a large light intensity. In such a case, if step ST14 is performed prior to at least one of step ST12 and step ST13, the subsequently measured first time waveform TW1 and / or second time waveform TW2 may lack accuracy. By performing step ST14 after step ST12 and step ST13, such a concern can be reduced.

[0119] Thereafter, as step ST15, the time response of the object B to be measured is obtained based on the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3. In this step ST15, based on the principle described above, the time response of the object B to be measured may be obtained by comparing the difference between the third time waveform TW3 and the first time waveform TW1 with the second time waveform TW2. This step ST15 corresponds to step ST6 shown in FIG. 12.

[0120] Points to note when generating the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 by the SLM14 will be described. From the SLM14, in addition to the first-order light, the -first-order light, etc. generated by the phase modulation, the non-modulated zero-order light is output. Different from the first-order light and the -first-order light, the zero-order light does not contribute to the formation of a desired time waveform. Therefore, when the pulse light P0 composed of the zero-order light temporally overlaps with the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3, the zero-order light will be detected simultaneously with the pump light and / or the probe light. For example, FIG. 29(a) shows a case where the component pulse P3 of the third pulse light PL3 overlaps with the pulse light P0 composed of the zero-order light. In such a case, the light intensity of the pump light and / or the probe light cannot be accurately detected.

[0121] Therefore, it is preferable to generate the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 with a temporal shift from the pulse light P0 composed of the zero-order light. For example, FIG. 29(b) shows a case where the third pulse light PL3 is generated after the pulse light P0. The time interval between the intensity peak of each of the first pulse light PL1 and the second pulse light PL2 and the intensity peak of the pulse light P0 is, for example, not less than 1 times and not more than 100 times the pulse widths W1, W2 of the first pulse light PL1 and the second pulse light PL2, respectively. Similarly, the time interval D2 between the intensity peak of the third pulse light PL3 (typically meaning the intensity peak of the component pulse P3) and the intensity peak of the pulse light P0 is, for example, not less than 2 times and not more than 100 times the pulse width (typically meaning the pulse width W4 of the component pulse P4) of the third pulse light PL3. In one embodiment, the time interval D2 is -1.5 ps.

[0122] Figures 30 and 31 are graphs showing an example of a time waveform TW5 which is a time waveform obtained by subtracting the second-hour waveform TW2 and the first-hour waveform TW1 from the third-hour waveform TW3. FIG. 30 shows a case where the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 temporally overlap with the pulse light P0. FIG. 31 shows a case where the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are generated 1.5 ps after the pulse light P0. As shown in FIG. 30, when the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 temporally overlap with the pulse light P0, it is difficult to separate the component of the pulse light P0 from the time waveform TW5. On the other hand, as shown in FIG. 31, when the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are generated sufficiently late from the pulse light P0, it is easy to separate the component of the pulse light P0 from the time waveform TW5.

[0123] The first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 may be generated before the pulse light P0 or may be generated after the pulse light P0. However, since the time response of the measurement object B continues for a long time after the pump light is irradiated, it is preferable that the pulse light P0 occurs before the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 (that is, the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are generated after the pulse light P0). [Wavelength dispersion measurement]

[0124] The measurement of the wavelength dispersion amount of the measurement object B using the optical property measurement device 1A of the present embodiment will be described. FIG. 32 is a diagram showing the operation of the optical property measurement device 1A when used as a wavelength dispersion measurement device. In the measurement of the wavelength dispersion amount, the optical system 4 is set to the second state, that is, a state in which the light attenuation unit 41 is not arranged on the optical path of the pulse light PL output from the measurement object B. Then, the pulse forming unit 3 forms an optical pulse train PL4 as the pulse light PL from the initial pulse light Pa. The optical pulse train PL4 includes optical pulses PLa, PLb, and PLc having a time difference from each other and different center wavelengths. The optical pulse train PL4 is a single pulse group generated using each wavelength band by dividing the spectrum constituting the initial pulse light Pa into a plurality of wavelength bands. Note that there may be overlapping portions at the boundaries of the plurality of wavelength bands. In the following description, the optical pulse train PL4 may be referred to as a "multi-pulse with band control".

[0125] FIG. 33 is a diagram showing an example of a multi-pulse with band control. In this example, an optical pulse train PL4 including three optical pulses PLa, PLb, and PLc is shown. FIG. 33(a) is a spectrogram, where the horizontal axis represents time and the vertical axis represents wavelength, and the light intensity is represented by the shade of color. FIG. 33(b) represents the time waveform of the optical pulse train PL4. The time waveforms of the respective optical pulses PLa, PLb, and PLc are, for example, in the shape of a Gaussian function. As shown in FIGS. 33(a) and 33(b), the peaks of the optical pulses PLa, PLb, and PLc are separated from each other in time, and the propagation timings of the optical pulses PLa, PLb, and PLc are shifted from each other. In other words, the optical pulses PLa, PLb, and PLc have a time difference from each other. The center wavelengths of the optical pulses PLa, PLb, and PLc are different from each other. The time interval (peak interval) of the optical pulses PLa, PLb, and PLc is, for example, in the range of 10 fs to 10000 fs, and in one example, it is 2000 fs. Also, the FWHM of the optical pulses PLa, PLb, and PLc is, for example, in the range of 10 fs to 5000 fs, and in one example, it is 300 fs.

[0126] Figure 33(c) shows the spectrum obtained by synthesizing the optical pulses PLa, PLb, and PLc. As shown in Figure 33(c), the spectrum obtained by synthesizing the optical pulses PLa, PLb, and PLc has a single peak. Referring to Figure 33(a), however, the central wavelengths of the optical pulses PLa, PLb, and PLc are shifted from each other. The single peak shown in Figure 33(c) approximately corresponds to the spectrum of the initial pulsed light Pa. The peak wavelength interval between adjacent optical pulses PLa, PLb (or PLb, PLc) is determined by the spectral bandwidth of the initial pulsed light Pa and is within a range approximately twice the full width at half maximum. In one example, when the spectral bandwidth of the initial pulsed light Pa is 10 nm, the peak wavelength interval is 5 nm. As a specific example, when the central wavelength of the initial pulsed light Pa is 1030 nm, the peak wavelengths of the optical pulses PLa, PLb, and PLc can be 1025 nm, 1030 nm, and 1035 nm, respectively.

[0127] Figure 34 shows, as a comparative example, a diagram of an example of a multi-pulse that is not band-controlled. In this example, an optical pulse train PL5 including three optical pulses PLd, PLe, and PLf is shown. Figure 34(a) is a spectrogram, similar to Figure 33(a), showing time on the horizontal axis and wavelength on the vertical axis, with the optical intensity represented by the shade of color. Figure 34(b) represents the time waveform of the optical pulse train PL5. Figure 34(c) shows the spectrum obtained by synthesizing the optical pulses PLd, PLe, and PLf. As shown in Figures 34(a) to (c), the peaks of the optical pulses PLd, PLe, and PLf are temporally separated from each other, but the central wavelengths of the optical pulses PLd, PLe, and PLf coincide with each other. When measuring the wavelength dispersion amount of the measurement object B, the pulse forming unit 3 generates an optical pulse train PL4 in which the central wavelengths are different from each other, as shown in Figure 33, instead of such an optical pulse train PL5.

[0128] FIG. 35(a) shows a specific example of the spectral waveform (spectral phase G21 and spectral intensity G22) given to the initial pulse light Pa by the SLM14 in order to generate the optical pulse train PL4. In FIG. 35(a), the horizontal axis represents the wavelength (nm), and the vertical axis represents the spectral intensity (arbitrary unit) and the spectral phase (rad). FIG. 35(b) is a graph showing the temporal intensity waveform of the optical pulse train PL4 generated by the spectral waveform shown in FIG. 35(a). In FIG. 35(b), the horizontal axis represents time (fs), and the vertical axis represents the optical intensity (arbitrary unit). The central wavelengths of the optical pulses PLa, PLb, and PLc are 1025 nm, 1030 nm, and 1035 nm, respectively.

[0129] The measurement object B is disposed on the optical axis of the optical pulse train PL4 output from the pulse forming unit 3. The optical pulse train PL4 output from the pulse forming unit 3 is irradiated onto the measurement object B. From the measurement object B, an optical pulse train PL4 that has passed through the measurement object B is output.

[0130] The measurement object B is, for example, a light guiding member such as an optical fiber or an optical waveguide. Examples of the optical fiber include a single mode fiber, a multi-mode fiber, a rare earth doped fiber, a photonic crystal fiber, a dispersion shifted fiber, or a double clad fiber. Examples of the optical waveguide include semiconductor micro waveguides such as SiN or InP. Alternatively, the measurement object B may be, for example, a semiconductor or a dielectric optical crystal. In that case, the measurement object B may be diamond, SiO2, LiNbO3, LiTaO3, PLZT, Si, Ge, fullerene, graphite, graphene, carbon nanotube, GaN, GaAs, a magnetic material, an organic material, or a polymer material, etc.

[0131] The optical pulse train PL4 that has passed through the optical system 4 is input to the correlation optical system 50. The correlation optical system 50 converts the optical pulse train PL4 into correlation light including cross-correlation or auto-correlation. The optical pulse train PL4 converted into correlation light is output from the correlation optical system 50.

[0132] FIG. 36(a) and FIG. 36(b) are diagrams for conceptually explaining the characteristic quantities of the correlation light of the optical pulse train PL4. FIG. 36(a) shows an example of the time waveform of the correlation light when the optical pulse train PL4 does not pass through the measurement object B. FIG. 36(b) shows an example of the time waveform of the correlation light when the optical pulse train PL4 passes through the measurement object B. Note that these examples show the case where the optical pulse train PL4 irradiated on the measurement object B includes the three optical pulses PLa, PLb, and PLc shown in FIG. 33(b). In this case, the correlation light is composed of three optical pulses PCa, PCb, and PCc corresponding to the optical pulses PLa, PLb, and PLc, respectively. Here, let the peak intensities of the optical pulses PCa, PCb, and PCc be PEa, PEb, and PEc, respectively, let the full width at half maximum (FWHM) of the optical pulses PCa, PCb, and PCc be Wa, Wb, and Wc, respectively, and let the peak time interval (pulse interval) between the optical pulses PCa and PCb be G a,b and let the peak time interval between the optical pulses PCb and PCc be G b,c and.

[0133] As shown in FIG. 36(a), when the optical pulse train PL4 does not pass through the measurement object B, the time waveform of the correlation light is almost the same as the time waveform of the optical pulse train PL4 immediately after being output from the pulse forming unit 3. In this example, for the peak intensity, PEb is larger than PEa and PEc, and PEa and PEb are almost equal. Also, for the full width at half maximum, Wa, Wb, and Wc are almost equal to each other. For the peak time interval, G a,b and G b,c are almost equal. On the other hand, as shown in FIG. 36(b), when the optical pulse train PL4 passes through the measurement object B, due to the wavelength dispersion of the measurement object B, the time waveform of the correlation light changes greatly from the time waveform of the optical pulse train PL4. In this example, the peak intensities PEa, PEb, and PEc of the optical pulses PCa, PCb, and PCc are significantly reduced compared to FIG. 36(a), and the full widths at half maximum Wa, Wb, and Wc of the optical pulses PCa, PCb, and PCc are significantly expanded compared to FIG. 36(a). Furthermore, the peak time interval G a,b is much longer compared to FIG. 36(a).

[0134] Thus, when the optical pulse train PL4 passes through the measurement object B, the characteristic quantities of the time waveform of the correlation light (peak intensities PEa, PEb, and PEc, full widths at half maximum Wa, Wb, and Wc, peak time intervals G a,b , G b,c ) change significantly compared to the case where the optical pulse train PL4 does not pass through the measurement object B. And the amount of change depends on the wavelength dispersion amount of the measurement object B. Therefore, by observing the change in the characteristic quantities of the time waveform of the correlation light, the wavelength dispersion amount of the measurement object B can be accurately and easily known. However, the wavelength dispersion amount of the measurement object B may be corrected using the known wavelength dispersion amount of the pulse laser light source 2.

[0135] FIG. 37 is a flowchart showing the wavelength dispersion measurement method of the present embodiment. This wavelength dispersion measurement method is a method for measuring the wavelength dispersion amount of the measurement object B, and is preferably implemented using, for example, the above-described optical property measurement apparatus 1A.

[0136] First, in the optical system 4, a second state (a state in which the light attenuation unit 41 is not arranged on the optical path of the pulsed light PL output from the measurement object B) is selected (step ST21). This step ST21 corresponds to step ST1 shown in FIG. 12. Next, as the pulsed light PL, an optical pulse train PL4 including a plurality of optical pulses PLa, PLb, and PLc having a time difference from each other and different center wavelengths from each other is generated in the pulse forming unit 3, and this optical pulse train PL4 is irradiated onto the measurement object B (step ST22). This step ST2 corresponds to step ST2 shown in FIG. 12. Subsequently, the time waveform of the optical pulse train PL4 that has passed through the measurement object B is measured in the waveform measurement unit 5 (step ST23). In step ST23, the time waveform of the optical pulse train PL4 may be measured by generating the correlation light of the optical pulse train PL4 using the correlation optical system 50. Subsequently, in the analysis unit 6, the wavelength dispersion amount of the measurement object B is estimated based on the characteristic quantities of the time waveform of the optical pulse train PL4 (step ST24).

[0137] The effects obtained by the optical property measurement apparatus 1A and the optical property measurement method according to the present embodiment described above will be described. In the optical property measurement apparatus 1A and the optical property measurement method according to the present embodiment, the number of pulses, spectrum, and temporal waveform of the pulsed light PL can be changed using the pulse forming unit 3, and the number of pulses, spectrum, and temporal waveform can be set according to the type of optical property to be measured. Further, an optical system 4 capable of mutually switching between a first state in which the light attenuation unit 41 is disposed on the optical path of the pulsed light PL output from the measurement object B and a second state in which the light attenuation unit 41 is not disposed on the optical path is used to set the presence or absence of the light attenuation unit 41 on the optical path. The attenuation rate of the light attenuation unit 41 with respect to one wavelength component constituting the pulsed light PL is larger than the attenuation rate of the light attenuation unit 41 with respect to another wavelength component constituting the pulsed light PL. Therefore, measurement of optical properties (for example, time response measurement) that requires attenuating one wavelength component constituting the pulsed light PL after passing through the measurement object B and measurement of optical properties (for example, wavelength dispersion measurement) that does not require attenuating after passing through the measurement object B can be performed using one apparatus. Thus, measurement of two or more types of optical properties, for example, time response measurement and wavelength dispersion measurement, can be performed using one apparatus.

[0138] As shown in FIG. 4, in the optical system 4, the light attenuation unit 41 may be movable in a direction intersecting the optical axis of the pulsed light PL. Alternatively, as shown in FIGS. 5 and 6, the optical system 4 has a configuration for mutually switching two optical paths for the pulsed light PL, and the light attenuation unit 41 may be disposed on either one of the two optical paths. By the optical system 4 having any one of these configurations, it is possible to easily switch between a first state in which the light attenuation unit 41 is disposed on the optical path and a second state in which the light attenuation unit 41 is not disposed on the optical path.

[0139] As in this embodiment, the types of optical characteristics to be measured include the time response inside the measurement object B caused by light irradiation and the amount of wavelength dispersion of the measurement object B. The optical system 4 may be in a first state during the measurement of the time response and in a second state during the measurement of the amount of wavelength dispersion. During the measurement of the time response, it is desirable to irradiate the measurement object B with pump light and probe light having different wavelengths, and then remove the pump light and measure only the probe light. In this case, the pump light corresponds to the one wavelength component, and the probe light corresponds to the other wavelength component. Further, during the measurement of the amount of wavelength dispersion, it is desirable to irradiate the measurement object B with an optical pulse train PL4 including a plurality of optical pulses PLa, PLb, and PLc having different wavelengths, and detect the time waveform of the optical pulse train PL4 that has passed through the measurement object B while maintaining the light intensity ratio of each wavelength component. By selecting the first state during the measurement of the time response and the second state during the measurement of the amount of wavelength dispersion in the optical system 4, the time response measurement and the wavelength dispersion measurement can be suitably performed.

[0140] As in this embodiment, the pulse forming unit 3 may form, as the pulsed light PL, an optical pulse train PL4 including a plurality of pulses PLa, PLb, and PLc having a time difference from each other and different center wavelengths during the measurement of the amount of wavelength dispersion. The waveform measurement unit 5 may measure the time waveform of the optical pulse train PL4 that has passed through the measurement object B. The analysis unit 6 may estimate the amount of wavelength dispersion of the measurement object B based on the feature amount of the time waveform of the optical pulse train PL4. Thereby, the amount of wavelength dispersion of the measurement object B can be suitably measured.

[0141] As in this embodiment, when measuring the time response, the pulse forming unit 3 may generate, as the pulsed light PL, a first pulsed light PL1 including the wavelength of the pump light, a second pulsed light PL2 including the wavelength of the probe light, and a third pulsed light PL3 including both the wavelength of the pump light and the wavelength of the probe light on a common optical axis. The attenuation rate of the dimming unit 41 with respect to the pump light may be greater than the attenuation rate of the dimming unit 41 with respect to the probe light. The waveform measuring unit 5 may measure a first time waveform TW1 that is the time waveform of the first pulsed light PL1 that has passed through the dimming unit 41, a second time waveform TW2 that is the time waveform of the second pulsed light PL2 that has passed through the dimming unit 41, and a third time waveform TW3 that is the time waveform of the third pulsed light PL3 that has passed through the dimming unit 41. The analysis unit 6 may obtain the time response of the measurement object B based on the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3.

[0142] As in this embodiment, when measuring the time response, steps ST2 and ST3 shown in FIG. 12 may be alternately repeated. In step ST12 corresponding to one repetition, the first pulsed light PL1, which is pulsed light PL including the wavelength of the pump light, is irradiated onto the measurement object B along a predetermined optical axis (step ST2), and the first time waveform TW1, which is the time waveform of the first pulsed light PL1 that has passed through the light attenuation unit 41 after being output from the measurement object B, may be measured (step ST3). Further, in step ST13 corresponding to another repetition, the second pulsed light PL2, which is pulsed light PL including the wavelength of the probe light, is irradiated onto the measurement object B along a predetermined optical axis (step ST2), and the second time waveform TW2, which is the time waveform of the second pulsed light PL2 that has passed through the light attenuation unit 41 after being output from the measurement object B, may be measured (step ST3). Further, in step ST14 corresponding to yet another repetition, the third pulsed light PL3, which is pulsed light PL including the wavelength of the probe light, is irradiated onto the measurement object B along a predetermined optical axis (step ST2), and the third time waveform TW3, which is the time waveform of the third pulsed light PL3 that has passed through the light attenuation unit 41 after being output from the measurement object B, may be measured (step ST3). Then, in step ST15 corresponding to step ST6 of obtaining the optical characteristics of the measurement object B, the time response of the measurement object B may be obtained based on the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3.

[0143] FIG. 47 is a schematic diagram showing the configuration of an apparatus 100 as a comparative example for measuring the time response of a measurement object 102. In the apparatus 100 shown in FIG. 47, the optical axis of the pump light Lpump when passing through the measurement object 102 is inclined with respect to the optical axis of the probe light Lprobe. In this case, in order to match the irradiation positions of the pump light Lpump and the probe light Lprobe inside the measurement object 102, it is necessary to adjust these irradiation positions on the order of micrometers. Therefore, the accuracy of spatial and temporal optical adjustment is required, and the work becomes extremely complicated.

[0144] To solve this problem, it is conceivable to align the optical axes of the pump light and the probe light with each other without inclining them, and irradiate the measurement object arranged on the aligned optical axis with the pump light and the probe light. As a result, since there is no need to perform an operation for aligning the irradiation position of the pump light and the irradiation position of the probe light, the measurement operation can be simplified. However, in that case, the probe light is detected as light in which the pump light is superimposed. Therefore, in order to measure the time response inside the measurement object caused by the irradiation of the pump light with the probe light, it is desirable to eliminate the influence of the pump light from the detection result. Thus, it is conceivable to remove only the pump light from the pump light and the probe light that have passed through the measurement object. However, usually, the light intensity of the pump light is much larger than the light intensity of the probe light. Therefore, even if only the pump light is attenuated using, for example, a wavelength filter, the pump light having a light intensity that cannot be ignored with respect to the light intensity of the probe light remains.

[0145] In the optical property measurement apparatus 1A and the optical property measurement method according to the present embodiment, a first pulse light PL1 including the wavelength of the pump light, a second pulse light PL2 including the wavelength of the probe light, and a third pulse light PL3 including the wavelengths of the pump light and the probe light are generated on a common optical axis. Then, after these first pulse light PL1, second pulse light PL2, and third pulse light PL3 are irradiated onto the measurement object B on the optical axis, the light intensity reducing unit 41 attenuates the light intensity of the light having the wavelength of the pump light. In this case, the first time waveform TW1, which is the time waveform of the first pulse light PL1 that has passed through the light intensity reducing unit 41, includes only the time waveform of the attenuated pump light. Further, the second time waveform TW2, which is the time waveform of the second pulse light PL2 that has passed through the light intensity reducing unit 41, includes only the time waveform of the probe light when the pump light is not irradiated. Further, the third time waveform TW3, which is the time waveform of the third pulse light PL3 that has passed through the light intensity reducing unit 41, includes a time waveform in which the time waveform of the probe light when the pump light is irradiated and the time waveform of the attenuated pump light are superimposed. Based on these time waveforms, it is possible to obtain the time response inside the measurement object B caused by the irradiation of the pump light from the time waveform of the probe light while eliminating the influence of the pump light by calculation.

[0146] In addition, according to the optical property measurement apparatus 1A of the present embodiment, the following operational effects can also be achieved. If the optical axis of the pump light when passing through the measurement object B is inclined with respect to the optical axis of the probe light, the region inside the measurement object B where the characteristic change occurs is limited to the region where the optical axis of the pump light and the optical axis of the probe light intersect each other, and that region is extremely small. Therefore, the influence of the characteristic change in that region on the probe light is also small. On the other hand, in the optical property measurement apparatus 1A of the present embodiment, the optical axis of the pump light when passing through the measurement object B and the optical axis of the probe light coincide with each other. Therefore, the region where the region inside the measurement object B where the characteristic change occurs overlaps with the irradiation region of the probe light extends along the optical axis of the probe light, and its volume becomes larger compared to the region when the optical axis of the pump light and the optical axis of the probe light intersect. Therefore, since the influence of the characteristic change in that region on the probe light also becomes larger, the time response inside the measurement object B can be obtained with higher accuracy.

[0147] As in the present embodiment, in the analysis unit 6 and step ST15, the time response of the measurement object B may be obtained based on the comparison between the difference between the third time waveform TW3 and the first time waveform TW1 and the second time waveform TW2. By calculating the difference between the third time waveform TW3 and the first time waveform TW1, the time waveform of the probe light when the pump light is irradiated can be obtained while eliminating the influence of the pump light. Then, by comparing this difference with the second time waveform TW2, the time waveform of the probe light when the pump light is irradiated and the time waveform of the probe light when the pump light is not irradiated are compared, and the time response inside the measurement object B can be obtained more accurately.

[0148] As in this embodiment, the pulse forming unit 3 may include an SLM 14 that generates the pulsed light PL by performing at least one of phase modulation and intensity modulation on the input initial pulsed light Pa. Similarly, in step ST2, the pulsed light PL may be generated using the SLM 14 that performs at least one of phase modulation and intensity modulation on the input initial pulsed light Pa. Further, the pulse forming unit 3 may include an SLM 14 that generates the pulsed light PL by simultaneously performing phase modulation and intensity modulation on the input initial pulsed light Pa. Similarly, in step ST2, the pulsed light PL may be generated using the SLM 14 that simultaneously performs phase modulation and intensity modulation on the input initial pulsed light Pa. In these cases, various pulsed lights PL can be selectively generated simply by changing the modulation pattern displayed on the SLM 14. Therefore, the pulsed light PL generated in the pulse forming unit 3 can be easily changed according to the type of optical characteristics to be measured.

[0149] As in this embodiment, the waveform measurement unit 5 may include a correlation optical system 50. The correlation optical system 50 is disposed downstream of the optical system 4 and outputs correlation light including the mutual correlation or auto-correlation of the pulsed light PL. Then, the analysis unit 6 may obtain the time response of the measurement object B based on this correlation light. In this case, even if the time width of the pulsed light PL is on the order of femtoseconds or picoseconds, its time waveform can be accurately measured. Therefore, the characteristic changes inside the measurement object B can be accurately measured.

[0150] As in this embodiment, the light attenuation unit 41 may include a wavelength filter that includes the wavelength of the pump light in the blocking band and includes the wavelength of the probe light in the transmission band. In this case, the light intensity of the wavelength of the pump light can be attenuated with a simple configuration.

[0151] As in this embodiment, in the pulse forming unit 3, the time interval D1 between the intensity peak of the component pulse P3 and the intensity peak of the component pulse P4 may be variable. In this case, it is easy to appropriately set the time interval D1 between the component pulse P3 and the component pulse P4 according to the type or property of the measurement object B.

[0152] As in this embodiment, in the pulse forming unit 3, the ratio (W3 / W4) of the pulse width W3 of the component pulse P3 to the pulse width W4 of the component pulse P4 may be variable. In this case, it is possible to easily set appropriately the ratio of the pulse width of the pump light included in the third pulse light PL3 to the pulse width of the probe light according to the type or property of the measurement object B.

[0153] As in this embodiment, the pulse width W3 of the component pulse P3 may be smaller than the pulse width W4 of the component pulse P4. For example, a method of performing the detection of the third pulse light PL3 a plurality of times while changing the time difference between the component pulse P4 having a pulse width W4 similar to the pulse width W3 and the component pulse P3 is also conceivable. According to this embodiment, unlike such a method, the measurement is completed by detecting the third pulse light PL3 only once. Therefore, since the number of irradiation times and the number of detection times of the third pulse light PL3 can be reduced, the measurement operation can be further simplified.

[0154] Here, an example of a method for determining the pulse width of the probe light, that is, the pulse width W2 of the second pulse light PL2 and the pulse width W4 of the component pulse P4 will be described. FIG. 38 is a graph showing the relationship between the pulse widths W2 and W4 and the time width Δt of the time response waveform of the measurement object B included in the time waveform TW5. In FIG. 38, the horizontal axis indicates the pulse widths W2 and W4 (ps), and the vertical axis indicates the time width Δt (ps). FIG. 38 shows the experimental results using a 1 mm thick ZnTe crystal as the measurement object B. FIG. 39 is a graph showing the time waveform TW5 on which several plots included in FIG. 38 are based. In FIG. 39, the horizontal axis indicates time (ps), and the vertical axis indicates light intensity (arbitrary unit). In FIG. 39, the line G31 is the result when the chirp amount of the second pulse light PL2 and the component pulse P4 is 15000 fs 2 and this is the result. The line G32 is the result when the chirp amount of the second pulse light PL2 and the component pulse P4 is 20000 fs 2 and this is the result. The line G33 is the result when the chirp amount of the second pulse light PL2 and the component pulse P4 is 40000 fs 2 and this is the result. The line G34 is the result when the chirp amount of the second pulse light PL2 and the component pulse P4 is 60000 fs2 This is the result. Note that the larger the chirp amount, the larger the pulse width.

[0155] Referring to FIG. 38, as the pulse widths W2 and W4 of the probe light increase, the time width Δt of the time response waveform of the measurement object B generally increases. However, within the range where the pulse widths W2 and W4 of the probe light are 400 fs or more and 600 fs or less, the time width Δt is almost a constant value. That is, within this range, it can be said that the time waveform TW5 hardly changes. The time width Δt within this range was 200 fs. From this, by determining the pulse widths W2 and W4 of the probe light within the range of 2 to 3 times the time response width of the measurement object B, the time response of the measurement object B can be measured with higher accuracy. [First Modified Example]

[0156] When measuring the time response of the measurement object B, the optical property measurement apparatus 1A according to the above embodiment may also measure the third-order nonlinear coefficient χ(3) of the measurement object B by adjusting the pulse widths W2 and W4 of the probe light.

[0157] FIGS. 40(a), 40(b), 41(a), 41(b), 42(a), and 42(b) show the chirp amounts of the second pulse light PL2 and the component pulse P4 as -5000 fs 2 , -2500 fs 2 , 0 fs 2 , 2500 fs 2 , 5000 fs 2 , and 10000 fs 2 respectively, and are graphs showing the time waveform TW5. In these figures, the horizontal axis represents time (ps), and the vertical axis represents light intensity (arbitrary unit). Referring to these figures, it can be seen that the phase of the time response waveform of the measurement object B changes according to the change in the chirp amount of the second pulse light PL2 and the component pulse P4, that is, the change in the pulse widths W2 and W4 of the probe light. Such a phenomenon occurs remarkably when the pulse widths W2 and W4 of the probe light are relatively small (for example, 400 fs or less).

[0158] When the measurement object B is irradiated with pump light, the refractive index of the measurement object B changes in the irradiated region. As a result, the time waveform of the probe light passing through the measurement object B is distorted. Such a phenomenon is called cross-phase modulation (XPM). And the magnitude of XPM depends on the third-order nonlinear coefficient χ(3) of the measurement object B. The change in the phase of the time response waveform of the measurement object B is considered to be due to this XPM. Therefore, it is possible to measure the third-order nonlinear coefficient χ(3) of the measurement object B by detecting the change in the phase of the time response waveform of the measurement object B included in the time waveform TW5. Note that the calculation of the third-order nonlinear coefficient χ(3) of the measurement object B based on the time waveform TW5 may be performed in the analysis unit 6. Further, the information used as the calculation source of the third-order nonlinear coefficient χ(3) is not limited to the time waveform TW5, and may be various information derived from the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3. [Second Modified Example]

[0159] FIG. 43 is a diagram showing the configuration of the optical property measurement apparatus 1B according to the second modified example of the present disclosure. In the optical property measurement apparatus 1B, the arrangement of the correlation optical system 50 is different from that of the optical property measurement apparatus 1A of the above embodiment. That is, in the optical property measurement apparatus 1B, the correlation optical system 50 is arranged on the optical path between the measurement object B and the optical system 40. In this case, the correlation optical system 50 receives the pulse light PL output from the measurement object B and generates the correlation light of the pulse light PL before attenuation.

[0160] The correlation light of the pulse light PL reaches the optical system 40. The optical system 40 passes the correlation light of the pulse light PL output from the correlation optical system 50. The optical system 40 has an attenuation unit 48. The attenuation rate of the attenuation unit 48 with respect to one wavelength component (for example, the correlation light of the pump light) constituting the pulse light PL is larger than the attenuation rate of the attenuation unit 48 with respect to another wavelength component (for example, the correlation light of the probe light) constituting the pulse light PL.

[0161] The optical system 40 is configured to be able to mutually switch between a first state in which the light attenuation unit 48 is disposed on the optical path of the pulsed light PL output from the correlation optical system 50 and a second state in which the light attenuation unit 48 is not disposed on the optical path. The optical system 40 is set to the first state when measuring the time response inside the measurement object B due to light irradiation, and is set to the second state when measuring the wavelength dispersion amount of the measurement object B. Note that the configurations of the optical system 40 and the light attenuation unit 48, except for the points described above, are the same as those in the above embodiment.

[0162] When measuring the time response inside the measurement object B, the light attenuation unit 48 transmits, without substantially attenuating, the wavelength components due to the probe light included in the correlation lights of the second pulsed light PL2 and the third pulsed light PL3, typically the correlation lights of the second pulsed light PL2 and the component pulse P4. Then, the light attenuation unit 48 attenuates the wavelength components due to the pump light included in the correlation lights of the first pulsed light PL1 and the third pulsed light PL3, typically the correlation lights of the first pulsed light PL1 and the component pulse P3. [Third Modification Example]

[0163] FIG. 44 is a diagram schematically showing the configuration of the waveform measurement unit 5A according to the third modification example of the present disclosure. The optical property measurement apparatus 1A of the above embodiment may include a waveform measurement unit 5A instead of the waveform measurement unit 5. The waveform measurement unit 5A has a long optical fiber 502 as an optical component replacing the correlation optical system 50. The long optical fiber 502 is an optical fiber having a sufficiently long length (for example, several km in length). The long optical fiber 502 is disposed at the subsequent stage of the optical system 4, and one end of the long optical fiber 502 is optically coupled to the optical system 4 via a lens 501. The other end of the long optical fiber 502 is optically coupled to a photodetector 51.

[0164] The pulsed light PL that has passed through the optical system 4 is incident on the long optical fiber 502. The long optical fiber 502 extends the time width of the pulsed light PL that propagates inside the long optical fiber 502. The long optical fiber 502 extends, for example, a pulse width on the femtosecond order to the nanosecond order. Each time waveform of the pulsed light PL with an extended time width is detected by the photodetector 51. Since the length and refractive index of the long optical fiber 502 are known, the analysis unit 6 calculates the time waveform of the pulsed light PL before the time width is extended from each detected time waveform, and measures the time response of the measurement object B based on the time waveform. Note that the waveform measurement unit 5B according to the second modification example may include the long optical fiber 502 as an optical component that replaces the correlation optical system 50. That is, the long optical fiber 502 may be disposed on the optical path between the measurement object B and the optical system 4.

[0165] As in this modification example, the waveform measurement unit 5A may include an optical component (long optical fiber 502) that is disposed between the measurement object B and the optical system 4 or at a subsequent stage of the optical system 4 to extend the time width of the pulsed light PL. In this case, even if the time width of the pulsed light PL is, for example, on the femtosecond order or picosecond order, these time waveforms can be measured accurately. Therefore, the optical characteristics of the measurement object B can be measured accurately.

[0166] Further, according to this modification example, since the pulsed light PL is detected with its time width expanded, a complicated optical system such as a correlation optical system is not required. In addition, when using a correlation optical system, it is necessary to perform detection while setting a plurality of time differences between the pulsed light PL and the reference pulsed light. However, according to this modification example, the time waveform of the pulsed light PL can be acquired with a smaller number of detections. Therefore, the measurement work can be simplified more. [Fourth Modification Example]

[0167] FIG. 45 is a diagram schematically showing the configuration of the waveform measurement unit 5B according to the fourth modification of the present disclosure. The optical component for stretching the time width of the pulsed light PL is not limited to the long optical fiber 502. For example, as shown in FIG. 45, instead of (or together with) the long optical fiber 502, a chirped fiber Bragg grating (CFBG) 504 may be arranged. The CFBG 504 has a diffraction grating pattern depicted on the optical fiber. In one example, the CFBG 504 is arranged between the optical system 4 and the photodetector 51 together with the optical circulator 503. The first port of the optical circulator 503 is optically coupled to the optical system 4, and the pulsed light PL that has passed through the measurement object B and the optical system 4 is input to the first port. The second port of the optical circulator 503 is optically coupled to the CFBG 504. The pulsed light PL input to the first port of the optical circulator 503 is output from the second port of the optical circulator 503 and input to the CFBG 504. The CFBG 504 stretches the time width of the pulsed light PL (for example, to the order of nanoseconds) in the same manner as the long optical fiber 502 described above. The pulsed light PL with the stretched time width is input to the second port of the optical circulator 503 again. The third port of the optical circulator 503 is optically coupled to the photodetector 51, and the pulsed light PL with the stretched time width is output from the third port and input to the photodetector 51. Note that the first port of the optical circulator 503 may be optically coupled to the measurement object B and the third port may be optically coupled to the optical system 4.

[0168] According to the configuration of this modification, the same effects as those of the third modification described above can be achieved. In addition, since the CFBG 504 is much smaller than the long optical fiber 502, the optical property measurement device can be miniaturized. Further, the propagation loss can be reduced as compared with the long optical fiber 502. [Fifth Modification]

[0169] The waveform measurement unit 5 of the above-described embodiment may have a spectral interference optical system as an optical system that replaces the correlation optical system 50. The spectral interference optical system branches the pulsed light PL into two, and generates interference fringes by causing the two branched pulsed lights PL to interfere with each other. Then, these interference fringes are measured using a spectroscope. In this case, even if the time width of the pulsed light PL is, for example, on the order of femtoseconds or picoseconds, these time waveforms can be accurately measured. Therefore, the optical characteristics of the measurement object B can be accurately measured. [Sixth Modification Example]

[0170] FIG. 46 is a diagram schematically showing the configuration of the optical characteristic measurement apparatus 1C according to the sixth modification example of the present disclosure. The optical characteristic measurement apparatus 1C is different from the optical characteristic measurement apparatus 1A according to the above-described embodiment in that it uses dual-comb spectroscopy instead of the correlation optical system 50. That is, the optical characteristic measurement apparatus 1C according to this modification example includes a waveform measurement unit 5C instead of the waveform measurement unit 5 of the above-described embodiment, and also includes a first pulsed laser light source 2A and a second pulsed laser light source 2B instead of the pulsed laser light source 2 of the above-described embodiment.

[0171] Both the first pulsed laser light source 2A and the second pulsed laser light source 2B are optical frequency comb light sources with stabilized pulse periods and offset frequencies, and periodically output femtosecond optical pulses composed of a mode group (comb mode group) arranged at equal frequency intervals. The first pulsed laser light source 2A and the second pulsed laser light source 2B are synchronized with each other in phase, and the periods for outputting femtosecond optical pulses are slightly different. The first pulsed laser light source 2A outputs an initial pulsed light Pa, and the second pulsed laser light source 2B outputs a reference pulsed light Pr. The initial pulsed light Pa output from the first pulsed laser light source 2A is converted into a pulsed light PL by the pulse forming unit 3. The pulsed light PL passes through the measurement object B and the optical system 4, and then is input to the waveform measurement unit 5C.

[0172] On the other hand, the reference pulse light Pr output from the second pulse laser light source 2B is directly input to the waveform measurement unit 5C without passing through the pulse formation unit 3, the measurement object B, and the optical system 4. At this time, the pulse light PL interferes with the reference pulse light Pr and is converted into interference light. The waveform measurement unit 5C has a photodetector 505. The photodetector 505 detects the interference light of the pulse light PL. This interference light is correlation light including the mutual correlation of the pulse light PL. Therefore, the second pulse laser light source 2B, the optical system that guides the pulse light PL to the waveform measurement unit 5C, and the optical system that guides the reference pulse light Pr to the waveform measurement unit 5C constitute a correlation optical system.

[0173] Here, both the first pulse laser light source 2A and the second pulse laser light source 2B periodically output femtosecond optical pulses, and their periods are slightly different. Therefore, a difference occurs between the timing when the pulse light PL is input to the photodetector 505 and the timing when the reference pulse light Pr is input to the photodetector 505, and this difference changes with time. Therefore, the photodetector 505 sequentially outputs an electrical signal representing the intensity of the correlation light while changing the time delay of the reference pulse light Pr with respect to the pulse light PL. As a result, electrical signals corresponding to optical signals obtained by sampling the time waveform of the pulse light PL at different timings can be sequentially acquired. The waveform measurement unit 5C measures the time waveform of the pulse light PL by processing the electrical signals sequentially acquired in this way.

[0174] In the correlation optical system 50B shown in FIG. 9, in order to sample the time waveform of the pulse light PL, it is necessary to move the mirror 58 mounted on the moving stage 59 to change the optical path length (that is, the time delay) of the reference pulse light Pr. Since there are limits to the amount of movement and the moving speed of the mirror 58, there are also limits to the dynamic range of the time response measurement and the time required for the time response measurement.

[0175] On the other hand, in the optical property measurement apparatus 1C according to this modification example, since a moving mirror is not used, the dynamic range of the time response measurement can be expanded and the time required for the time response measurement can be shortened compared to the optical property measurement apparatus 1A including the correlation optical system 50B shown in FIG. 9.

[0176] The optical property measurement apparatus and the optical property measurement method according to the present disclosure are not limited to the above-described embodiments, and various other modifications are possible. For example, the above-described embodiments and each modification example may be combined with each other according to necessary purposes and effects.

Description of Reference Numerals

[0177] 1A, 1B, 1C... Optical property measurement device, 2, 2A, 2B... Pulse laser light source, 3... Pulse formation unit, 3a... Light input end, 3b... Light output end, 4, 4A, 4B, 4C, 40... Optical system, 5, 5A, 5B, 5C... Waveform measurement unit, 6... Analysis unit, 12... Diffraction grating, 13... Lens, 14... Spatial light modulator (SLM), 15... Lens, 16... Diffraction grating, 17... Modulation surface, 17a... Modulation region, 18... Control unit, 20... Modulation pattern calculation device, 21... Arbitrary waveform input unit, 22... Phase spectrum design unit, 23... Intensity spectrum design unit, 24... Modulation pattern generation unit, 25... Fourier transform unit, 26... Function substitution unit, 27... Waveform function correction unit, 28... Inverse Fourier transform unit, 29... Target generation unit, 29a... Fourier transform unit, 29b... Spectrogram correction unit, 41, 48... Light attenuation unit, 43a, 43b... Fixed mirror, 44a, 44b... Movable mirror, 45a, 45b... Half mirror, 46a, 46b... Fixed mirror, 47... Light absorber, 50, 50A, 50B, 50C... Correlation optical system, 50c, 50d, 50e, 50f... Optical path, 51... Photodetector, 52a, 52b... Lens, 53... Optical element, 54... Beam splitter, 55, 56, 58... Mirror, 57, 59... Moving stage, 61... Processor (CPU), 62... ROM, 64... Input device, 65... Output device, 66... Communication module, 67... Auxiliary storage device, 100... Device, 102... Measurement object, 501... Lens, 502... Long optical fiber, 503... Optical circulator, 504... Chirped fiber Bragg grating (CFBG), 505... Photodetector, AA, AB... Direction, B... Measurement object, D1, D2... Time interval, Lprobe... Probe light, Lpump... Pump light, P0... (0th order) Pulse light, P3, P4... Component pulses, Pa... Initial pulse light, Pb... Light, Pc... Modulated light, PCa, PCb, PCc... Light pulses, PEa, PEb... Peak intensity, PL... Pulse light, PL1... First pulse light, PL2... Second pulse light, PL3... Third pulse light, PL4, PL5... Light pulse train, PLa, PLb, PLc, PLd, PLe, PLf... Light pulses, Pr... Reference pulse light, PLu, PLv... Pulse light, T1, T2, T3, T4... Peak intensity, TW1, TW2, TW3, TW4, TW5... Time waveform, W1, W2, W3, W4... Pulse width, Wa, Wb... Full width at half maximum.

Claims

1. An apparatus for measuring the optical properties of a measurement object, comprising: a pulse forming unit that generates a pulsed light and can change the temporal waveform of the pulsed light according to the type of the optical property to be measured; a waveform measurement unit that measures the temporal waveform of the pulsed light output from the measurement object after being irradiated on the measurement object; an optical system having a light attenuation unit in which the attenuation rate for one wavelength component constituting the pulsed light is larger than the attenuation rate for another wavelength component constituting the pulsed light, the optical system being capable of mutually switching between a first state in which the light attenuation unit is disposed on the optical path of the pulsed light output from the measurement object and a second state in which the light attenuation unit is not disposed on the optical path; an analysis unit that obtains the optical properties of the measurement object based on the temporal waveform; wherein the optical properties to be measured include a temporal response inside the measurement object caused by light irradiation and a wavelength dispersion amount of the measurement object, and the optical system is in the first state during measurement of the temporal response and in the second state during measurement of the wavelength dispersion amount.

2. The optical property measurement apparatus according to claim 1, wherein in the optical system, the light attenuation unit is movable in a direction intersecting the optical axis of the pulsed light.

3. The optical system has a configuration for mutually switching between two optical paths for the pulsed light, and the light attenuation unit is disposed on one of the two optical paths.

4. During measurement of the temporal response, the pulse forming unit generates, on a common optical axis, a first pulsed light including the wavelength of a pump light, a second pulsed light including the wavelength of a probe light, and a third pulsed light including the wavelengths of the pump light and the probe light as the pulsed light, the attenuation rate of the light attenuation unit for the pump light is larger than the attenuation rate of the light attenuation unit for the probe light, the waveform measurement unit measures a first temporal waveform that is the temporal waveform of the first pulsed light that has passed through the light attenuation unit, a second temporal waveform that is the temporal waveform of the second pulsed light that has passed through the light attenuation unit, and a third temporal waveform that is the temporal waveform of the third pulsed light that has passed through the light attenuation unit, and the analysis unit obtains the temporal response of the measurement object based on the first temporal waveform, the second temporal waveform, and the third temporal waveform.

5. ​ The optical property measurement device according to claim 4, wherein the analysis unit obtains the time response of the measurement object based on a comparison between the difference between the third time waveform and the first time waveform and the second time waveform.

6. The optical property measurement device according to claim 4 or 5, wherein, in the pulse forming unit, the time interval between the intensity peak of the component of the wavelength of the pump light included in the third pulse light and the intensity peak of the component of the wavelength of the probe light is variable.

7. The optical property measurement device according to any one of claims 4 to 6, wherein, in the pulse forming unit, the ratio of the pulse width of the component of the wavelength of the pump light included in the third pulse light to the pulse width of the component of the wavelength of the probe light is variable.

8. The optical property measurement device according to any one of claims 4 to 7, wherein the pulse width of the component of the wavelength of the pump light included in the third pulse light is smaller than the pulse width of the component of the wavelength of the probe light included in the third pulse light.

9. When measuring the amount of wavelength dispersion, the pulse forming unit forms an optical pulse train including a plurality of pulses having a time difference from each other and different central wavelengths as the pulse light. The waveform measurement unit measures the time waveform of the optical pulse train that has passed through the measurement object. The optical property measurement device according to any one of claims 1 to 8, wherein the analysis unit estimates the amount of wavelength dispersion of the measurement object based on the feature amount of the time waveform of the optical pulse train.

10. The optical property measurement device according to any one of claims 1 to 9, wherein the pulse forming unit includes a spatial light modulator that generates the pulse light by performing at least one of phase modulation and intensity modulation of the input light.

11. The waveform measurement unit is disposed between the measurement object and the optical system or at a subsequent stage of the optical system, and has a correlation optical system that converts the pulse light into correlation light including cross-correlation or auto-correlation. The optical property measurement device according to any one of claims 1 to 10, wherein the analysis unit obtains the optical property of the measurement object based on the pulse light converted into correlation light.

12. The optical property measurement device according to any one of claims 1 to 11, wherein the waveform measurement unit is disposed between the measurement object and the optical system or at a subsequent stage of the optical system, and has an optical component that extends the time width of the pulse light.

13. The optical property measurement apparatus according to any one of claims 1 to 12, wherein the light attenuation unit has a wavelength filter that includes the wavelength of the one wavelength component within a blocking band and includes the wavelength of the other wavelength component within a transmission band.

14. A method for measuring the optical properties of a measurement object by irradiating the measurement object with pulsed light, In an optical system capable of mutually switching between a first state in which a light attenuation unit having a greater attenuation rate for one wavelength component constituting the pulsed light than for another wavelength component constituting the pulsed light is disposed on the optical path of the pulsed light output from the measurement object, and a second state in which the light attenuation unit is not disposed on the optical path, a step of selecting any state; A step of irradiating the measurement object with the pulsed light having a time waveform corresponding to the type of the measured optical property, using a pulse forming unit capable of changing the time waveform of the pulsed light; A step of measuring the time waveform of the pulsed light that has passed through the optical system; A step of obtaining the optical properties of the measurement object based on the time waveform; including The types of the measured optical properties include the time response inside the measurement object due to light irradiation and the wavelength dispersion amount of the measurement object. In the step of selecting the state, the first state is selected during measurement of the time response, and the second state is selected during measurement of the wavelength dispersion amount. An optical property measurement method.

15. During measurement of the time response, the steps of irradiating and measuring are alternately repeated. In one step of irradiating, a first pulsed light that is the pulsed light including the wavelength of the pump light is irradiated onto the measurement object along a predetermined optical axis, and in the step of measuring following the step of irradiating, a first time waveform that is the time waveform of the first pulsed light that has passed through the light attenuation unit after being output from the measurement object is measured. In another step of irradiating, a second pulsed light that is the pulsed light including the wavelength of the probe light is irradiated onto the measurement object along the predetermined optical axis, and in the step of measuring following the step of irradiating, a second time waveform that is the time waveform of the second pulsed light that has passed through the light attenuation unit after being output from the measurement object is measured. In yet another said irradiating step, a third pulsed light which is the pulsed light including the wavelength of the pump light and the wavelength of the probe light is irradiated onto the object to be measured along the predetermined optical axis. In the said measuring step following the irradiating step, a third time waveform which is the time waveform of the third pulsed light output from the object to be measured and then passing through the light attenuation unit is measured. In the step of obtaining the optical characteristics of the object to be measured, the time response of the object to be measured is obtained based on the first time waveform, the second time waveform, and the third time waveform. The optical characteristic measurement method according to claim 14.

16. In the step of obtaining the optical characteristics, the time response of the object to be measured is obtained based on the comparison between the difference between the third time waveform and the first time waveform and the second time waveform. The optical characteristic measurement method according to claim 15.

17. The pulse width of the component of the wavelength of the pump light included in the third pulsed light is made smaller than the pulse width of the component of the wavelength of the probe light included in the third pulsed light. The optical characteristic measurement method according to claim 15 or 16.

18. The third time waveform is measured after the first time waveform and the second time waveform are measured. The optical characteristic measurement method according to any one of claims 15 to 17.

19. When measuring the wavelength dispersion amount, in the said irradiating step, as the pulsed light, an optical pulse train including a plurality of pulses having a time difference from each other and different central wavelengths is irradiated onto the object to be measured. in the said measuring step, the time waveform of the optical pulse train passing through the object to be measured is measured. in the step of obtaining the optical characteristics, the wavelength dispersion amount of the object to be measured is estimated based on the characteristic amount of the time waveform of the optical pulse train. The optical characteristic measurement method according to claim 14.

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