Time response measurement device and time response measurement method

Abstract

To provide a time response measuring device and a time response measurement method capable of simplifying a measurement work.SOLUTION: A time response measuring device 1A includes a pulse forming part 3, a dimming part 4, a waveform measurement part 5, and an analysis part 6. The pulse forming part 3 generates first pulse light PL1 including a wavelength of pump light, second pulse light PL2 including a wavelength of probe light, and third pulse light PL3 including a wavelength of pump light and a wavelength of probe light, on a common light axis. The dimming part 4 passes the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 which are outputted from a sample B after being applied to the sample B. An attenuation factor of the dimming part 4 to the pump light is larger than an attenuation factor of the dimming part 4 to the probe light. The waveform measurement part 5 measures respective time waveforms of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 passing through the dimming part 4. The analysis part 6 obtains a time response of the sample B on the basis of the time waveforms.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a time response measurement device and a time response measurement method.

Background Art

[0002] Patent Document 1 discloses a technique related to a distributed measurement device. This distributed measurement device 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 central 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 central 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] A method (time-resolved spectroscopy measurement method) is known in which a sample is irradiated with pump light and probe light having different wavelengths, and a change in the characteristics inside the sample caused by the irradiation of the pump light is evaluated based on the temporal change of the probe light output from the sample. FIG. 36 is a diagram schematically showing an apparatus 100 conventionally used for time-resolved spectroscopy measurement. Probe light Lprobe output from a light source 101 passes through a sample 102 and is incident on a photodetector 103. Pump light Lpump output from the light source 101 passes through the sample 102 after the time difference from the probe light Lprobe is adjusted by a delay optical system 104. The optical axis of the pump light Lpump when passing through the sample 102 is inclined with respect to the optical axis of the probe light Lprobe. Thereby, only the probe light Lprobe can be detected without detecting the pump light Lpump at the photodetector 103. Then, while changing the time difference between the pump light Lpump and the probe light Lprobe imparted in the delay optical system 104, the temporal change in the light intensity of the probe light Lprobe incident on the photodetector 103 is observed. In this way, a change in the characteristics inside the sample 102 caused by the irradiation of the pump light Lpump can be evaluated based on the temporal change of the probe light Lprobe output from the sample 102.

[0007] In the apparatus 100 shown in FIG. 36, as described above, the optical axis of the pump light Lpump when passing through the sample 102 is inclined with respect to the optical axis of the probe light Lprobe. In this case, inside the sample 102, in order to make the irradiation positions of the pump light Lpump and the probe light Lprobe coincide with each other, it is necessary to adjust these irradiation positions on the order of micrometers. Therefore, high precision in spatial and temporal optical adjustment is required, and the work becomes extremely complicated.

[0008] The present disclosure has been made in view of such problems, and an object thereof is to provide a time response measurement apparatus and a time response measurement method that can simplify the measurement work.

Means for Solving the Problems

[0009] In order to solve the above-described problems, a time response measurement apparatus according to the present disclosure is an apparatus that measures the time response inside a sample caused by light irradiation, and includes a pulse formation unit, an optical attenuation unit, a waveform measurement unit, and an analysis unit. The pulse formation unit generates 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. The optical attenuation unit allows the first pulse light, the second pulse light, and the third pulse light output from the sample after being irradiated to the sample disposed on the optical axis to pass therethrough. The attenuation rate of the optical attenuation unit with respect to the pump light is larger than the attenuation rate of the optical attenuation unit with respect to the probe light. The waveform measurement unit measures a first time waveform that is the time waveform of the first pulse light that has passed through the optical attenuation unit, a second time waveform that is the time waveform of the second pulse light that has passed through the optical attenuation unit, and a third time waveform that is the time waveform of the third pulse light that has passed through the optical attenuation unit. The analysis unit obtains the time response of the sample based on the first time waveform, the second time waveform, and the third time waveform.

[0010] When the optical axes of the pump light and the probe light are made to coincide without inclining them with respect to each other, and the sample disposed on the coincident optical axis is irradiated with the pump light and the probe light, the probe light is detected as the light overlaid with the pump light. In order to measure the time response inside the sample caused by the irradiation of the pump light by means of 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 out of the pump light and the probe light that have passed through the sample. However, usually, the light intensity of the pump light is significantly larger than the light intensity of the probe light, and thus 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 the light intensity of the probe light. Therefore, even if only the pump light is attenuated using a wavelength filter with an attenuation rate of 99%, for example, the pump light with a light intensity approximately equal to that of the probe light remains.

[0011] Therefore, in the above-described time response measurement apparatus, 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 sample on the optical axis, the light intensity of the light having the wavelength of the pump light is attenuated by the light attenuation unit. Therefore, the first time waveform, which is the time waveform of the first pulsed light that has passed through the light attenuation unit, 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 attenuation unit, 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 attenuation unit, includes the 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 overlaid. Based on these time waveforms, it is possible to obtain the time response inside the sample 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.

[0012] Thus, according to the above-described time response measurement apparatus, the optical axes of the pump light and the probe light are made to coincide without inclining them with respect to each other, and the sample disposed on the coincident optical axis is irradiated with the pump light and the probe light, whereby the time response inside the sample can be measured. Therefore, unlike the apparatus 100 shown in FIG. 36, 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, so that the measurement operation can be simplified.

[0013] In addition, the above-described time response measurement apparatus can also exhibit the following operational effects. In the apparatus 100 shown in FIG. 36, the optical axis of the pump light Lpump when passing through the sample 102 is inclined with respect to the optical axis of the probe light Lprobe. Therefore, the region inside the sample where the characteristic change occurs is limited to the region where the optical axis of the pump light Lpump and the optical axis of the probe light Lprobe intersect with each other, and that region is extremely small. Thus, the influence of the characteristic change in that region on the probe light Lprobe is also small. On the other hand, in the above-described time response measurement apparatus, the optical axis of the pump light when passing through the sample coincides with the optical axis of the probe light. Therefore, the region where the region inside the sample where the characteristic change occurs overlaps with the irradiation region of the probe light extends along the optical axis, and its volume becomes larger compared to the case of FIG. 36. Thus, the influence of the characteristic change in that region on the probe light also becomes larger, so that the time response inside the sample can be obtained with higher accuracy.

[0014] In the above-described time response measurement apparatus, the analysis unit may obtain the time response of the sample 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, 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, which is the time waveform of the probe light when the pump light is not irradiated, the time response inside the sample can be obtained more accurately.

[0015] In the above-described time response measurement apparatus, the pulse forming unit may include a spatial light modulator that generates the first pulse light, the second pulse light, and the third pulse light by simultaneously performing phase modulation and intensity modulation on the input pulsed light. In this case, since the first pulse light, the second pulse light, and the third pulse light can be selectively generated simply by changing the modulation pattern displayed on the spatial light modulator, the pulsed light generated in the pulse forming unit can be easily changed among the first pulse light, the second pulse light, and the third pulse light.

[0016] In the pulse forming unit of the above-described time response measurement apparatus, 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 may be variable. In this case, it is possible to easily set appropriately the time interval between the pump light and the probe light included in the third pulse light according to the type or property of the sample.

[0017] In the pulse forming unit of the above-described time response measurement apparatus, 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 may be variable. In this case, it is possible to easily set appropriately the ratio of the pulse width of the pump light to the pulse width of the probe light included in the third pulse light according to the type or property of the sample.

[0018] In the above-described time response measurement apparatus, the pulse width of the component of the wavelength of the pump light included in the third pulse light may be smaller than the pulse width of the component of the wavelength 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 approximately the same as the width of the pump light and the pump light, the measurement operation can be further simplified.

[0019] In the above-described time response measurement apparatus, the waveform measurement unit is disposed between the sample and the light attenuation unit or at a subsequent stage of the light attenuation unit, and has a correlation optical system that converts the first pulsed light, the second pulsed light, and the third pulsed light into correlation light including cross-correlation or auto-correlation. The analysis unit may obtain the time response of the sample based on the first pulsed light, the second pulsed light, and the third pulsed light that have been converted into correlation light. Alternatively, the waveform measurement unit may be disposed between the sample and the light attenuation unit or at a subsequent stage of the light attenuation unit, and may have optical components that extend the time widths of the first pulsed light, the second pulsed light, and the third pulsed light. In these cases, even if the time widths of the first pulsed light, the second pulsed light, and the third pulsed light are, for example, on the femtosecond order or the picosecond order, these time waveforms can be accurately measured. Therefore, changes in characteristics inside the sample can be accurately measured.

[0020] In the above-described time response measurement apparatus, the light attenuation unit may have a wavelength filter that includes the wavelength of the pump light within the cutoff band and includes the wavelength of the probe light within the transmission band. In this case, the light intensity of the light having the wavelength of the pump light can be attenuated with a simple configuration.

[0021] The time response measurement method according to the present disclosure is a method for measuring the time response inside a sample caused by light irradiation. The method includes: irradiating a sample with a first pulsed light including the wavelength of pump light along a predetermined optical axis, and measuring a first time waveform that is the time waveform of the first pulsed light that has passed through a light attenuation unit that attenuates the light intensity of the light having the wavelength of the pump light after being output from the sample; irradiating the sample with a second pulsed light including the wavelength of probe light along the predetermined optical axis, and measuring 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 sample; irradiating the sample with a third pulsed light including the wavelengths of the pump light and the probe light along the predetermined optical axis, and measuring a third time waveform that is the time waveform of the third pulsed light that has passed through the light attenuation unit after being output from the sample; and obtaining the time response of the sample based on the first time waveform, the second time waveform, and the third time waveform.

[0022] According to this time response measurement method, similar to the above-described time response measurement apparatus, based on the first time waveform, the second time waveform, and the third time waveform, the time response inside the sample caused by the irradiation of the pump light can be obtained from the time waveform of the probe light while eliminating the influence of the pump light by calculation. In addition, the time response inside the sample can be measured by making the optical axes of the pump light and the probe light coincide with each other without inclining them, and irradiating the sample arranged on the coincident optical axis with the pump light and the probe light. Therefore, since there is no need to perform an operation to align the irradiation position of the pump light and the irradiation position of the probe light, the measurement operation can be simplified.

[0023] In the step of obtaining the time response of the above time response measurement method, the time response of the sample 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, 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, 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 sample can be obtained more accurately.

[0024] In the steps of measuring the first time waveform, the second time waveform, and the third time waveform of the above time response measurement method, the first pulse light, the second pulse light, and the third pulse light may be generated using a spatial light modulator that simultaneously performs phase modulation and intensity modulation of the input pulsed light. In this case, since the first pulse light, the second pulse light, and the third pulse light can be selectively generated only by changing the modulation pattern displayed on the spatial light modulator, the pulsed light generated in the pulse forming section can be easily changed among the first pulse light, the second pulse light, and the third pulse light.

[0025] In the above-described time response measurement 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, it is possible to measure the characteristic change inside the sample without setting a plurality of time differences between the pump light and the probe light. Therefore, the measurement work can be further simplified.

[0026] In the above-described time response measurement method, a step of measuring a third time waveform may be performed after the step of measuring the first time waveform and the step of measuring 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 sample, 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.

Advantages of the Invention

[0027] According to the present disclosure, it is possible to provide a time response measurement apparatus and a time response measurement method that can simplify the measurement work.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32

Figure 33

Figure 34

Figure 35

Figure 36

DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of a time response measurement apparatus and a time response 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 elements are denoted by the same reference numerals, and redundant descriptions are omitted. In the present disclosure, unless otherwise specified, the time waveform means a time waveform related to the light intensity.

[0030] FIG. 1 is a diagram schematically showing the configuration of a time response measurement apparatus 1A according to an embodiment of the present disclosure. This time response measurement apparatus 1A is an apparatus for measuring the time response inside a sample B caused by light irradiation, and includes a pulse laser light source 2, a pulse formation unit 3, an optical attenuation unit 4, a waveform measurement unit 5, and an analysis unit 6. The light input end 3a of the pulse formation 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 formation unit 3 is optically coupled to the sample B spatially or via an optical waveguide such as an optical fiber. Further, the sample B is optically coupled to the waveform measurement unit 5 spatially or via an optical waveguide such as an optical fiber. The optical attenuation unit 4 is disposed on the optical path between the sample 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 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 pulse light Pa is, for example, Gaussian-shaped. The full width at half maximum (FWHM) of the pulse light Pa is, for example, in the range of 10 fs to 10000 fs, and in one example, is 100 fs. This 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 pulse light Pa is 10 nm, and the central wavelength of the pulse light Pa is 1030 nm.

[0032] The pulse forming unit 3 generates the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 from the pulsed light Pa on a common optical axis reaching the sample B. The pulse forming unit 3 can output these first pulse light PL1, second pulse light PL2, and third pulse light PL3 individually at arbitrary timings with a time interval between each other. The output order of the first pulse light PL1, second pulse light PL2, and third pulse light PL3 is also arbitrary. In one example, the third pulse light PL3 is output after the first pulse light PL1 and the second pulse light PL2 are output.

[0033] The (a) part of FIG. 2 schematically shows the time waveform of the first pulse light PL1. The wavelength band of the first pulse 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 pulsed light Pa. The wavelength of the pump light is, for example, in the range of 770 nm to 820 nm. The first pulse light PL1 may consist only of light having the wavelength of the pump light. The time waveform of the first pulse light PL1 is, for example, in the shape of a Gaussian function.

[0034] Part (b) of FIG. 2 schematically shows the time waveform of the second pulsed light PL2. The wavelength band of the second pulsed light PL2 includes the wavelength of the probe light. The wavelength of the probe light is included in the wavelength components of the pulsed light Pa that are longer than the wavelength of the pump light among the plurality of wavelength components included in the pulsed 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 pulsed light Pa. The wavelength of the probe light is, for example, in the range of 820 nm to 840 nm. The second pulsed light PL2 may consist only of light having the wavelength of the probe light. A part of the wavelength band of the second pulsed light PL2 may overlap with a part of the wavelength band of the first pulsed light PL1. The time waveform of the second pulsed light PL2 is, for example, Gaussian-shaped. The peak intensity T2 of the second pulsed light PL2 is smaller than the peak intensity T1 of the first pulsed light PL1. For example, the peak intensity T2 of the second pulsed light PL2 is 1 / 10 or less of the peak intensity T1 of the first pulsed light PL1. Also, the pulse width W2, which is the full width at half maximum of the second pulsed light PL2, is larger than the pulse width W1, which is the full width at half maximum of the first pulsed light PL1. For example, the pulse width W2 of the second pulsed light PL2 is 1 times or more and 100 times or less of the pulse width W1 of the first pulsed light PL1.

[0035] FIG. 3 is a diagram for explaining the time waveform and the spectral waveform of the third pulsed light PL3. Part (a) of FIG. 3 is a spectrogram, where the horizontal axis represents time, the vertical axis represents wavelength, and the light intensity is represented by the shade of color. Part (b) of FIG. 3 shows the time waveforms of the component pulses P3 and P4 included in the third pulsed light PL3. Part (c) of FIG. 3 shows the spectral waveform obtained by synthesizing the component pulses P3 and P4, that is, the spectral waveform of the third pulsed light PL3.

[0036] 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.

[0037] As shown in part (c) of FIG. 3, the spectrum obtained by synthesizing the component pulses P3 and P4 has a single peak. However, referring to part (a) of FIG. 3, the central wavelengths of the component pulses P3 and P4 are shifted from each other. The single peak shown in part (c) of FIG. 3 approximately corresponds to the spectrum of the pulse light Pa. The peak wavelength interval between the component pulses P3 and P4 is determined by the spectral bandwidth of the 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 pulse light Pa.

[0038] 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 sample B. The time interval D1 may be zero. Also, in the pulse forming unit 3, the ratio (W3 / W4) of the pulse width W3 of the component (component pulse P3) of the wavelength of the pump light included in the third pulse light PL3 to 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 sample B. In this case, the ratio (W1 / W2) of the pulse width W1 of the first pulse light PL1 to the pulse width W2 of the second pulse light PL2 is also changed accordingly.

[0039] FIG. 4 is a diagram showing a configuration example of the pulse forming unit 3. The pulse forming 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 pulse 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 pulse light Pa is incident obliquely on the diffraction grating 12 and is split into a plurality of wavelength components. The light Pb including this 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 a concave mirror having a concave light reflecting surface.

[0040] SLM14 imparts a phase shift for each wavelength to the pulsed light Pa in order to convert the pulsed light Pa into the first pulsed light PL1, the second pulsed light PL2, or the third pulsed light PL3. Specifically, SLM14 receives a control signal from the control unit 18 in order to impart a phase shift to the pulsed light Pa and generate the first pulsed light PL1, the second pulsed light PL2, or the third pulsed light PL3. 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 simultaneously performs 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 drawings, SLM14 may be a reflective type.

[0041] FIG. 5 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 from other wavelength components in each modulation region 17a. When SLM14 is a phase modulation type, the intensity modulation is realized by the phase pattern (phase image) presented on the modulation surface 17.

[0042] Each wavelength component of the modulated light Pc modulated by the SLM14 is focused on 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 a light transmissive 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 first pulse light PL1, the second pulse light PL2, or the third pulse light PL3.

[0043] The control unit 18 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 SLM14.

[0044] FIG. 6 schematically shows an example of the spectral waveform (spectral phase G11 and spectral intensity G12) given to the pulse light Pa by the third phase pattern. In FIG. 6, the horizontal axis represents the wavelength, and the vertical axis represents each value of the spectral intensity and the spectral phase. However, FIG. 6 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. 6, the wavelength characteristic of the spectral phase G11 has a portion G11a that is constant in a band smaller than a certain wavelength λ A and a portion G11b that is a downward 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 ω B are angular frequencies, ω(λ)=2πc / λ, ω B =2πc / λ B (c is the speed of light). The wavelength λ at which the portion G11b becomes a minimum value Bis greater than the wavelength λ A Also, the wavelength λ A is greater than the peak wavelength λ C of the spectral intensity. The portion 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 portion 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 portion forming the component pulse P3 and the portion forming the component pulse P4 becomes discontinuous.

[0045] The sample B is disposed 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 sample B. From the sample B, the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have passed through the sample 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 sample B may be output from the sample B. The sample 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.

[0046] The (a) part of FIG. 7 is a graph schematically showing an example of the time waveform of the probe light that has passed through sample B when the pump light does not irradiate sample B. The (b) part of FIG. 7 is a graph schematically showing an example of the time waveform of the probe light that has passed through sample B when the pump light irradiates sample B at time t0. Note that in the (b) part of FIG. 7, the graph shown in the (a) part of FIG. 7 is indicated by a dashed-dotted line. In this example, when the optical characteristics of sample B change at time t0 when the pump light is irradiated, the light transmittance of sample B with respect to the wavelength of the probe light rapidly decreases. Thereafter, the light transmittance of sample 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. 7, as shown in the (c) part of FIG. 7, the time response of sample B to the irradiation of the pump light can be obtained.

[0047] The light attenuation unit 4 allows the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 output from sample B to pass through. At this time, the light attenuation unit 4 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 4 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 4 with respect to the wavelength of the pump light is greater than the attenuation rate of the light attenuation unit 4 with respect to the wavelength of the probe light. In one example, the light attenuation unit 4 has a wavelength filter 41. The wavelength filter 41 includes the wavelength of the pump light within the cutoff band and includes the wavelength of the probe light within the transmission band. The wavelength filter 41 may be any of a band-pass filter, a high-pass filter, and a low-pass filter. The transmittance of the wavelength filter 41 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 41 with respect to the wavelength of the probe light is, for example, in the range of 50% to 99%.

[0048] FIG. 8 is a graph showing an example of superimposing a first time waveform TW1 which is a time waveform of the first pulsed light PL1 that has passed through the light attenuation unit 4, a second time waveform TW2 which is a time waveform of the second pulsed light PL2 that has passed through the light attenuation unit 4, and a third time waveform TW3 which is a time waveform of the third pulsed light PL3 that has passed through the light attenuation unit 4. In FIG. 8, 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 4. The third time waveform TW3 includes a waveform obtained by superimposing the time waveform of the pump light attenuated by the light attenuation unit 4 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 sample B. The evaluation of the time response inside the sample B based on the above principle is performed by an analysis unit 6 described later.

[0049] 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 calculations based on the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3 is arbitrary. FIG. 9 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. 9, the horizontal axis represents time (ps), and the vertical axis represents light intensity (arbitrary unit). For example, as shown in FIG. 9, 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.

[0050] Refer to FIG. 1 again. The waveform measurement unit 5 measures the time waveforms of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have passed through the light attenuation unit 4, that is, the first time waveform TW1, the second time waveform TW2, and the third time waveform TW3. The waveform measurement unit 5 of the present embodiment includes a correlation optical system 50 and a photodetector 51.

[0051] The correlation optical system 50 is optically coupled to the light attenuation unit 4 and 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 4. 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.

[0052] FIG. 10 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 light attenuation unit 4 and the optical element 53, and condenses the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have passed through the light attenuation unit 4 onto the optical element 53. The optical element 53 is a light emitter including at least one of, for example, a non-linear optical crystal that generates second harmonic generation (SHG) and a phosphor. Examples of the non-linear 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 first pulse light PL1, the second pulse light PL2, and the third pulse light PL3, and converts each of 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 lens 52b collimates or condenses the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have been converted into correlation light and output from the optical element 53. Note that the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are converted into correlation light in order to detect the time waveform with higher accuracy.

[0053] Here, a configuration example of the correlation optical system 50 will be described in detail. In the following description, the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are expressed as pulse light PL.

[0054] FIG. 11 is a diagram schematically showing a correlation optical system 50A for converting incident pulse 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 splitting the pulse light PL into two branches. The beam splitter 54 is optically coupled to the light attenuation unit 4, transmits a part of the pulse light PL input from the light attenuation unit 4, and reflects the remaining part. The branching ratio of the beam splitter 54 is, for example, 1:1. One pulse light PLa branched by the beam splitter 54 reaches the lens 52a through an optical path 50c including a plurality of mirrors 55. The other pulse light PLb 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 pulse light PLa and the other pulse light PLb 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 pulse light PLa and the pulse light PLb can be made variable.

[0055] In this example, the optical element 53 includes a nonlinear optical crystal. The lens 52a condenses each of the pulse lights PLa and PLb toward the optical element 53, and intersects the optical axes of the pulse lights PLa and PLb 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 pulse lights PLa and PLb. This second harmonic wave is correlation light and includes the autocorrelation of the pulse light PL. The correlation light is parallelized or condensed by the lens 52b and then input to the photodetector 51.

[0056] FIG. 12 is a diagram schematically showing a correlation optical system 50B for converting a pulsed light PL into a correlation light including a mutual 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 the moving stage 59, and the optical length of the optical path 50f is variable. Therefore, in this configuration, the time difference (the timing difference of reaching the lens 52a) between the pulsed light PL and the reference pulsed light Pr can be made variable.

[0057] 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 mutual correlation of the pulsed light PL. This correlation light is parallelized or condensed by the lens 52b and then input to the photodetector 51.

[0058] FIG. 13 is a diagram schematically showing a correlation optical system 50C for converting a pulsed light PL into a correlation light including a mutual 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 the first polarization direction. On the other hand, the polarization plane of the 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 pulsed light Pa includes a polarization component in the first polarization direction (arrow Dp1 in the figure) and a polarization component in the second polarization direction orthogonal to the first polarization direction (symbol Dp2 in the figure). Further, the polarization state of the pulsed light Pa is not limited to the above polarization state (oblique linearly polarized light), and may be elliptically polarized light.

[0059] Of the pulsed light Pa, the polarization component in the first polarization direction is modulated by the SLM 14 and output from the pulse forming unit 3 as the pulsed light PL. On the other hand, the polarization component in the second polarization direction of the pulsed light Pa is not modulated by the SLM 14 and is directly output from the pulse forming unit 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 preferably generated in the correlation optical system 50C.

[0060] As shown in FIGS. 11 to 13, the correlation optical system 50 is an optical system that spatially and temporally overlaps the pulsed light PL with the pulsed light PL itself or another pulsed light. Specifically, by temporally sweeping one of the pulsed lights, 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 that the respective temporal waveforms (the first temporal waveform TW1, the second temporal waveform TW2, and the third temporal waveform TW3) of the pulsed light PL, that is, the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3, are detected with higher accuracy.

[0061] Referring again to FIG. 1, the photodetector 51 receives the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have been converted into correlation light and output from the correlation optical system 50. The photodetector 51 detects the time waveforms of these first pulse light PL1, second pulse light PL2, and third pulse light PL3. The photodetector 51 is configured to include a photodetector (photodetector) such as a photodiode, for example. The photodetector 51 detects the time waveforms of the first pulse light PL1, second pulse light PL2, and third pulse light PL3 by converting the intensities of the first pulse light PL1, second pulse light PL2, and third pulse light PL3 into electrical signals. The electrical signal that is the detection result is provided to the analysis unit 6.

[0062] The analysis unit 6 is electrically connected to the photodetector 51. The analysis unit 6 obtains the time response of the sample B based on the time waveforms of the first pulse light PL1, second pulse light PL2, and third pulse light PL3 that have been respectively converted into correlation light. The time waveforms of the first pulse light PL1, second pulse light PL2, and third pulse light PL3 that have been respectively converted into correlation light have correlations with the first time waveform TW1 that is the time waveform of the first pulse light PL1 that has passed through the light attenuation unit 4, the second time waveform TW2 that is the time waveform of the second pulse light PL2 that has passed through the light attenuation unit 4, and the third time waveform TW3 that is the time waveform of the third pulse light PL3 that has passed through the light attenuation unit 4, respectively. Therefore, the principle described above for obtaining the time response inside the sample B based on the first time waveform TW1, second time waveform TW2, and third time waveform TW3 can be directly applied even when the first pulse light PL1, second pulse light PL2, and third pulse light PL3 are converted into correlation light. The analysis unit 6 can be configured by, for example, a computer. The analysis unit 6 may be configured by a computer separate from the control unit 18 (see FIG. 4), or may be configured by a computer common to the control unit 18.

[0063] FIG. 14 is a diagram schematically showing a hardware configuration example of the analysis unit 6 and the control unit 18. As shown in FIG. 14, 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, an auxiliary storage device 67 such as a hard disk, and the like, and can be configured as a normal computer.

[0064] The auxiliary storage device 67 of the control unit 18 stores data related to a phase modulation pattern for generating the first pulsed light PL1, data related to a phase modulation pattern for generating the second pulsed light PL2, and data related to a phase modulation pattern for generating the third pulsed light PL3. 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.

[0065] In addition, the auxiliary storage device 67 of the analysis unit 6 stores a program for obtaining the time response of the sample B based on the time waveforms of the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3, which are respectively converted into correlation light. In other words, the program for obtaining the time response of the sample B causes the processor 61 of the computer to operate as the analysis unit 6. The processor 61 obtains the time response of the sample B by executing this program. The storage device that stores the program for obtaining the time response of the sample B may be a non-temporary recording medium. Examples of the recording medium include recording media such as a flexible disk, a CD, and a DVD, recording media such as a ROM, a semiconductor memory, a cloud server, and the like. Information regarding the obtained time response of the sample B is output to the output device 65 or output to an external device via the communication module 66.

[0066] Here, the time response measurement method of the present embodiment will be described. FIG. 15 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 sample B caused by light irradiation, and is preferably implemented using, for example, the above-described time response measurement device 1A.

[0067] First, as step ST1, the first pulsed light PL1 is irradiated onto the sample 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 4 after being output from the sample B, is measured. Next, as step ST2, the second pulsed light PL2 is irradiated onto the sample B along the above-described 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 4 after being output from the sample B, is measured. Subsequently, as step ST3, the third pulsed light PL3 is irradiated onto the sample B along the above-described 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 4 after being output from the sample B, is measured. In these steps ST1 to ST3, the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 are generated using the SLM14 that simultaneously performs phase modulation and intensity modulation of the input pulsed light Pa.

[0068] The order of these steps ST1 to ST3 is arbitrary, and step ST2 may be performed first, or step ST3 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 sample B, irreversible characteristic changes may occur when irradiating light having a large light intensity. In such a case, if step ST3 is performed prior to at least one of step ST1 and step ST2, the subsequently measured first time waveform TW1 and / or second time waveform TW2 may lack accuracy. By performing step ST3 after step ST1 and step ST2, such a concern can be reduced.

[0069] Thereafter, as step ST4, the time response of sample B is obtained based on the first-time waveform TW1, the second-time waveform TW2, and the third-time waveform TW3. In this step ST4, based on the principle described above, the time response of sample 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.

[0070] Here, the phase modulation for generating the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 in the SLM14 of the pulse forming unit 3 shown in FIG. 4 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 time intensity waveform in the time region. Therefore, the output light from the pulse forming unit 3 can have various time intensity waveforms (the first-time waveform TW1, the second-time waveform TW2, and the third-time waveform TW3) different from the pulse light Pa according to the modulation pattern of the SLM14.

[0071] FIG. 16 is a diagram showing the configuration of a modulation pattern calculation device 20 that calculates the modulation pattern of the SLM14. 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. 4 may also serve as the modulation pattern calculation device 20. The modulation pattern calculation device 20 calculates a phase modulation pattern for making the time intensity waveform of the output light of the pulse forming unit 3 approach a desired waveform, and provides the phase modulation pattern to the control unit 18. The modulation pattern is data for controlling the SLM14, 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 (Computer-Generated Holograms (CGH)).

[0072] The modulation pattern calculation device 20 of the present 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. 16, 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.

[0073] 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.

[0074] 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 time-intensity waveform to the arbitrary waveform input unit 21. The information regarding the desired time-intensity waveform is, for example, the pulse width W1 and peak intensity T1 of the first pulsed light PL1 shown in Fig. 2(a), the pulse width W2 and peak intensity T2 of the second pulsed light PL2 shown in Fig. 2(b), the pulse widths W3, W4 and peak intensities T3, T4 of the third pulsed light PL3 shown in Fig. 3(b), and the time interval D1 shown in Fig. 3(b). The magnitudes of these numerical values are arbitrary and variable. The information regarding the desired time-intensity waveform 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 forming unit 3 suitable for realizing the given desired time-intensity waveform. The intensity spectrum design unit 23 calculates the intensity spectrum of the output light of the pulse forming unit 3 suitable for realizing the given desired time-intensity waveform. The modulation pattern generation unit 24 calculates a phase modulation pattern (e.g., a computer-generated hologram) for applying the phase spectrum obtained in the phase spectrum design unit 22 and the intensity spectrum obtained in the intensity spectrum design unit 23 to the output light of the pulse forming unit 3.

[0075] Fig. 17 is a block diagram showing the internal configurations of the phase spectrum design unit 22 and the intensity spectrum design unit 23. As shown in Fig. 17, 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.

[0076] 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 performing an iterative Fourier transform based on the desired time-intensity waveform. FIG. 18 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

[0077] 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

Number

Number

Number

[0078] 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).

Number

[0079] 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 (band wavelengths) 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. 19 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)). Here, i is an imaginary number.

Number

[0080] 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

[0081] 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

[0082] 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]

[0083] 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.

[0084] Here, time-frequency conversion means performing frequency filter processing or numerical operation processing (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".

[0085] 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), etc.

[0086] Read out the target spectrogram TargetSG0(ω,t) generated in advance 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 that make it up), and is generated in the target spectrogram function of the process number (15b).

[0087] 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, the process proceeds to process number (16); if not, the process proceeds 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).

[0088] 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)).

Equation

[0089] FIG. 20 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).

[0090] 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)).

Equation

[0091] Subsequently, in processing number (17), the filter processing unit of the intensity spectrum design unit 23 performs a filter process 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 where it is greater than the intensity spectrum function A0(ω), the value of the intensity spectrum function A TWC-TFD (ω) takes on the value of the intensity spectrum function A0(ω). For 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 on the value of the intensity spectrum function αB 0,k (ω) (processing number (17) in the figure).

Equation

[0092] The modulation pattern generation unit 24 calculates a phase modulation pattern (e.g., 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.

[0093] FIG. 21 is a diagram showing an example of a procedure for generating 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 (initial intensity spectral function A0(ω) and 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)).

[0094] 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. 18 (processing number (22)).

[0095] 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 previously obtained phase spectral function Φ IFTA (ω) (processing number (23)). FIG. 22 is a diagram showing an example of a procedure for calculating the intensity spectral function A IFTA (ω).

[0096] Referring to FIG. 22, 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

[0097] 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

[0098] 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 a desired waveform (processing numbers (34) and (35) in the figure).

Number

Number

[0099] 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

[0100] In addition, for the intensity spectrum function C(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(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 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(ω)). In that case, as shown in the following mathematical formula (u), at frequencies where the intensity spectrum function C(ω) is greater than the intensity spectrum function A(ω), the value of the intensity spectrum function A(ω) is incorporated as the value of the intensity spectrum function A(ω). At frequencies where the intensity spectrum function C(ω) is less than or equal to the intensity spectrum function A(ω), the value of the intensity spectrum function C(ω) is incorporated as the value of the intensity spectrum function A(ω) (processing number (37b) in the figure). k (ω), filtering based on the intensity spectrum of the input light is performed. Specifically, among the intensity spectra represented by the intensity spectrum function C k (ω), the portion exceeding the cut-off intensity for each wavelength determined based on the intensity spectrum of the input light is cut off. As an 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), at frequencies where the intensity spectrum function C k (ω) is greater 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). At frequencies where the intensity spectrum function C k (ω) is less than or equal to 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(ω) included in the above function (s) with the intensity spectrum function A(ω) after the filtering process according to the above mathematical formula (u). k (ω) with the intensity spectrum function A k (ω) after the filtering process according to the above mathematical formula (u).

[0101] Thereafter, by repeating the above processes (32) to (37b), the intensity spectrum shape represented by the intensity spectrum function A(ω) in the waveform function can be made closer to the intensity spectrum shape corresponding to the desired time-intensity waveform. Finally, the intensity spectrum function A(ω) is obtained. k (ω) can be made closer to the intensity spectrum shape corresponding to the desired time-intensity waveform. Finally, the intensity spectrum function A IFTA (ω) is obtained.

[0102] Referring again to FIG. 21, 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). As a result, a fourth waveform function (w) in the time domain is obtained (processing number (25)). [Number]

[0103] 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 relevant part are manipulated based on the time function p0(t). Hereinafter, specific examples thereof will be described in detail.

[0104] 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. 23(a). In Fig. 23(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. 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.

[0105] If one only wants to control 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 one wants to control the frequency (wavelength) band of each pulse, the operation of these domains D1, D2, and D3 is required. That is, as shown in Fig. 23(b), moving each of the domains D1, D2, and D3 independently 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).

[0106] 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 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. 23(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.

[0107] 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 phase modulation, unmodulated 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. 24(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.

[0108] Therefore, it is advisable 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. 24(b) shows a case where the third pulse light PL3 is generated after the pulse light P0. The time intervals between the intensity peaks of the first pulse light PL1 and the second pulse light PL2, respectively, and the intensity peak of the pulse light P0 are, 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.

[0109] FIG. 25 and FIG. 26 are graphs showing an example of a time waveform TW5 which is a time waveform obtained by subtracting the second time waveform TW2 and the first time waveform TW1 from the third time waveform TW3. FIG. 25 shows a case where the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 temporally overlap the pulse light P0. FIG. 26 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. 25, when the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 temporally overlap 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. 26, 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.

[0110] 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 sample 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).

[0111] The effects obtained by the time response measurement apparatus 1A and the time response measurement method according to the present embodiment described above will be described. As described above, in the apparatus 100 shown in FIG. 36, the optical axis of the pump light Lpump when passing through the sample 102 is inclined with respect to the optical axis of the probe light Lprobe. In this case, in order to match the irradiation position of the pump light Lpump and the irradiation position of the probe light Lprobe inside the sample 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.

[0112] In order 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 sample disposed 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 sample 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 sample. 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, pump light having a light intensity that cannot be ignored with respect to the light intensity of the probe light remains.

[0113] In the time response measurement apparatus 1A and the time response measurement method of 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 sample B on the optical axis, the light intensity reducing unit 4 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 4, 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 4, 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 4, 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 sample 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.

[0114] In addition, according to the above-described time response measurement device 1A and time response measurement method, the following operational effects can also be achieved. In the device 100 shown in FIG. 36, the optical axis of the pump light Lpump when passing through the sample 102 is inclined with respect to the optical axis of the probe light Lprobe. Therefore, the region inside the sample 102 where the characteristic change occurs is limited to the region where the optical axis of the pump light Lpump and the optical axis of the probe light Lprobe intersect each other, and that region is extremely small. Thus, the influence of the characteristic change in that region on the probe light Lprobe is also small. On the other hand, in the time response measurement device 1A of the present embodiment, the optical axis of the pump light and the optical axis of the probe light coincide with each other when passing through the sample B. Therefore, the region where the region inside the sample 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 case of FIG. 36. Thus, the influence of the characteristic change in that region on the probe light also becomes larger, so that the time response inside the sample B can be obtained with higher accuracy.

[0115] As in the present embodiment, in the analysis unit 6 and step ST4, the time response of the sample 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, 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. 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 sample B can be obtained more accurately.

[0116] Like in this embodiment, the pulse forming unit 3 may have an SLM 14 that simultaneously performs phase modulation and intensity modulation on the input pulsed light Pa to generate the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3. Similarly, in steps ST1, ST2, and ST3, the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 may be generated using the SLM 14 that simultaneously performs phase modulation and intensity modulation on the input pulsed light Pa. In this case, the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 can be selectively generated simply by changing the modulation pattern displayed on the SLM 14. Therefore, the pulsed light generated in the pulse forming unit 3 can be easily changed among the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3.

[0117] Like in this embodiment, the waveform measurement unit 5 may have a correlation optical system 50. The correlation optical system 50 is arranged downstream of the light attenuation unit 4 and outputs correlation light including the mutual correlation or autocorrelation of the first pulsed light PL1, correlation light including the mutual correlation or autocorrelation of the second pulsed light PL2, and correlation light including the mutual correlation or autocorrelation of the third pulsed light PL3. Then, the analysis unit 6 may obtain the time response of the sample B based on this correlation light. In this case, even if the time widths of the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 are, for example, on the femtosecond order or picosecond order, the time waveform having a correlation with these pulse waveforms can be accurately measured. Therefore, the characteristic changes inside the sample B can be accurately measured.

[0118] Like in this embodiment, the light attenuation unit 4 may have a wavelength filter 41 that includes the wavelength of the pump light within the cutoff band and includes the wavelength of the probe light within the transmission band. In this case, the light intensity of the wavelength of the pump light can be attenuated with a simple configuration.

[0119] As in the present 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 possible to easily set the time interval D1 between the component pulse P3 and the component pulse P4 appropriately according to the type or property of the sample B.

[0120] As in the present 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 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 appropriately according to the type or property of the sample B.

[0121] As in the present 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 detecting the third pulse light PL3 a plurality of times while changing the time difference between the component pulse P4 having a pulse width W4 approximately equal to the pulse width W3 and the component pulse P3 is also conceivable. According to the present embodiment, unlike such a method, the measurement is completed by detecting the third pulse light PL3 only once. Therefore, since the number of irradiations and detections of the third pulse light PL3 can be reduced, the measurement work can be further simplified.

[0122] 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. 27 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 sample B included in the time waveform TW5. In FIG. 27, the horizontal axis indicates the pulse widths W2 and W4 (ps), and the vertical axis indicates the time width Δt (ps). FIG. 27 shows the experimental results using a 1 mm thick ZnTe crystal as the sample B. FIG. 28 is a graph showing the time waveform TW5 on which several plots included in FIG. 27 are based. In FIG. 28, the horizontal axis indicates time (ps), and the vertical axis indicates light intensity (arbitrary unit). In FIG. 28, the line G21 indicates that the chirp amount of the second pulse light PL2 and the component pulse P4 is 15000 fs 2This is the result. The line G22 shows the case where the chirp amounts of the second pulse light PL2 and the component pulse P4 are 20000 fs 2 This is the result. The line G23 shows the case where the chirp amounts of the second pulse light PL2 and the component pulse P4 are 40000 fs 2 This is the result. The line G24 shows the case where the chirp amounts of the second pulse light PL2 and the component pulse P4 are 60000 fs 2 This is the result. Note that the larger the chirp amount, the larger the pulse width.

[0123] Referring to FIG. 27, as the pulse widths W2 and W4 of the probe light increase, the time width Δt of the time response waveform of the sample 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 times or more and 3 times or less the time response width of the sample B, the time response of the sample B can be measured with higher accuracy. [First Modified Example]

[0124] The time response measurement device 1A of the above embodiment measures only the time response of the sample B. As described below, the time response measurement device 1A may also measure the third-order nonlinear coefficient χ(3) of the sample B by adjusting the pulse widths W2 and W4 of the probe light.

[0125] FIGS. 29(a), 29(b), 30(a), 30(b), 31(a), and 31(b) show the cases where the chirp amounts of the second pulse light PL2 and the component pulse P4 are -5000 fs 2 , -2500 fs 2 , 0 fs 2 , 2500 fs 2 , 5000 fs 2 , and 10000 fs 2It is a graph showing the time waveform TW5 when [conditions are met]. In these figures, the horizontal axis represents time (ps), and the vertical axis represents optical intensity (arbitrary unit). Referring to these figures, it can be seen that the phase of the time response waveform of sample 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 significantly when the pulse widths W2 and W4 of the probe light are relatively small (for example, 400 fs or less).

[0126] When the sample B is irradiated with the pump light, the refractive index of the sample B changes in the irradiated region. As a result, the time waveform of the probe light passing through the sample 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 sample B. The change in the phase of the time response waveform of the sample B is considered to be due to this XPM. Therefore, it is possible to measure the third-order nonlinear coefficient χ(3) of the sample B by detecting the change in the phase of the time response waveform of the sample B included in the time waveform TW5. Note that the calculation of the third-order nonlinear coefficient χ(3) of the sample B based on the time waveform TW5 may be performed in the analysis unit 6 shown in FIG. 1. 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]

[0127] FIG. 32 is a diagram showing the configuration of the time response measurement device 1B according to the second modified example of the present disclosure. In the time response measurement device 1B, the arrangement of the correlation optical system 50 is different from that of the time response measurement device 1A in the above embodiment. That is, in the time response measurement device 1B, the correlation optical system 50 is arranged on the optical path between the sample B and the light attenuation unit 4A. In this case, the correlation optical system 50 receives the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 output from the sample B, and generates the correlation lights of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 before light attenuation.

[0128] These correlation lights reach the light attenuation unit 4A. The light attenuation unit 4A allows these correlation lights output from the correlation optical system 50 to pass through. At this time, the light attenuation unit 4A transmits, without substantially attenuating, the wavelength components due to the probe light included in the correlation lights of the second pulse light PL2 and the third pulse light PL3, typically the correlation lights of the second pulse light PL2 and the component pulse P4. Then, the light attenuation unit 4A attenuates the wavelength components due to the pump light included in the correlation lights of the first pulse light PL1 and the third pulse light PL3, typically the correlation lights of the first pulse light PL1 and the component pulse P3. In other words, in the light attenuation unit 4A, the attenuation rate for the wavelength component of the correlation light due to the pump light is larger than the attenuation rate for the wavelength component of the correlation light due to the probe light. In one example, the light attenuation unit 4A has a wavelength filter 42. The wavelength filter 42 includes the wavelength of the correlation light due to the pump light within the blocking band and includes the wavelength of the correlation light due to the probe light within the transmission band. The wavelength filter 42 may be any of a band-pass filter, a high-pass filter, and a low-pass filter. [Third Modified Example]

[0129] FIG. 33 is a diagram schematically showing the configuration of the waveform measurement unit 5A according to the third modified example of the present disclosure. The time response measurement device 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, a length of several km). The long optical fiber 502 is disposed at the subsequent stage of the light attenuation unit 4, and one end of the long optical fiber 502 is optically coupled to the light attenuation unit 4 via a lens 501. The other end of the long optical fiber 502 is optically coupled to a photodetector 51.

[0130] The first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have passed through the light attenuation unit 4 are incident on the long optical fiber 502. The long optical fiber 502 extends the time widths of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that propagate inside the long optical fiber 502. The long optical fiber 502 extends, for example, a pulse width on the order of femtoseconds to the order of nanoseconds. Each time waveform of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 with extended time widths 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 waveforms of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 before the time widths are extended from the detected time waveforms, and measures the time response of the sample B based on the time waveforms. 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 sample B and the light attenuation unit 4.

[0131] As in this modification example, the waveform measurement unit 5A may be disposed between the sample B and the light attenuation unit 4 or at a subsequent stage of the light attenuation unit 4 and include an optical component (long optical fiber 502) that extends the time widths of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3. In this case, even if the time widths of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are, for example, on the order of femtoseconds or picoseconds, these time waveforms can be accurately measured. Therefore, the characteristic changes inside the sample B can be accurately measured.

[0132] Further, according to this modified example, since the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 are detected with their time widths expanded, a complex optical system such as a correlation optical system is not required. Also, when using a correlation optical system, it is necessary to perform detection while setting a plurality of time differences between the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 and the reference pulsed light. However, according to this modified example, the time waveforms of the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3 can be obtained by each single detection. Therefore, the measurement work can be made simpler. [Fourth Modified Example]

[0133] FIG. 34 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 widths of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 is not limited to the long optical fiber 502. For example, as shown in FIG. 34, a chirped fiber Bragg grating (CFBG) 504 may be arranged instead of (or together with) the long optical fiber 502. The CFBG 504 has a diffraction grating pattern depicted on an optical fiber. In one example, the CFBG 504 is arranged between the light attenuator 4 and the photodetector 51 together with the optical circulator 503. The first port of the optical circulator 503 is optically coupled to the light attenuator 4, and the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 that have passed through the light attenuator 4 are input to the first port. The second port of the optical circulator 503 is optically coupled to the CFBG 504. The first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 input to the first port of the optical circulator 503 are output from the second port of the optical circulator 503 and input to the CFBG 504. The CFBG 504 stretches the time widths of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 (for example, to the order of nanoseconds) in the same manner as the long optical fiber 502 described above. The first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 with the stretched time widths are 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 first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 with the stretched time widths are 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 sample B, and the third port may be optically coupled to the light attenuator 4.

[0134] 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 time response measurement device can be miniaturized. Further, the propagation loss can be reduced as compared with the long optical fiber 502. [Fifth Modification]

[0135] The waveform measurement unit 5 of the above 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 probe light into two, and generates interference fringes by causing the two branched probe lights to interfere with each other. Then, these interference fringes are measured using a spectroscope. In this case, by analyzing the difference between the interference fringes of the probe light when the second pulse light PL2, that is, the pump light, is not irradiated and the interference fringes of the probe light when the component pulse P4, that is, the pump light, is irradiated, a signal including the time response of the sample B can be obtained. [Sixth Modification Example]

[0136] FIG. 35 is a diagram schematically showing the configuration of the time response measurement apparatus 1C according to the sixth modification example of the present disclosure. The time response measurement apparatus 1C is different from the time response measurement apparatus 1A according to the above embodiment in that it uses dual-comb spectroscopy instead of the correlation optical system 50. That is, the time response measurement apparatus 1C according to this modification example includes a waveform measurement unit 5C instead of the waveform measurement unit 5 of the above embodiment, and also includes a first pulse laser light source 2A and a second pulse laser light source 2B instead of the pulse laser light source 2 of the above embodiment.

[0137] Both the first pulse laser light source 2A and the second pulse laser light source 2B are optical frequency comb light sources in which the pulse period and the offset frequency are stabilized, and periodically output femtosecond optical pulses composed of a mode group (comb mode group) arranged at equal frequency intervals. The first pulse laser light source 2A and the second pulse laser light source 2B are synchronized with each other in phase, and the periods for outputting femtosecond optical pulses are slightly different. The first pulse laser light source 2A outputs a pulse light Pa, and the second pulse laser light source 2B outputs a reference pulse light Pr. The pulse light Pa output from the first pulse laser light source 2A is converted into a first pulse light PL1, a second pulse light PL2, and a third pulse light PL3 by the pulse shaping unit 3. The first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 pass through the sample B and the light attenuation unit 4 and then are input to the waveform measurement unit 5C.

[0138] 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 sample B, and the light attenuation unit 4. At this time, the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are converted into interference light by interfering with the reference pulse light Pr. The waveform measurement unit 5C has a photodetector 505. The photodetector 505 detects the interference light of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3. These interference lights are correlation lights including the cross-correlation of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3. Therefore, the second pulse laser light source 2B, the optical system that guides the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 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.

[0139] 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 first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 are input to the photodetector 505 and the timing when the reference pulse light Pr is input to the photodetector 505, and the 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 first pulse light PL1, the second pulse light PL2, and the third pulse light PL3. As a result, electrical signals corresponding to optical signals obtained by sampling the time waveforms of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 at different timings can be sequentially acquired. The waveform measurement unit 5C measures the time waveforms of the first pulse light PL1, the second pulse light PL2, and the third pulse light PL3 by processing the electrical signals sequentially acquired in this way.

[0140] In the correlation optical system 50B shown in FIG. 12, in order to sample the time waveforms of the first pulsed light PL1, the second pulsed light PL2, and the third pulsed light PL3, it is necessary to move the mirror 58 mounted on the moving stage 59 to change the optical path length (i.e., time delay) of the reference pulsed 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.

[0141] On the other hand, in the time response measurement device 1C according to this modification, 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 time response measurement device 1A including the correlation optical system 50B shown in FIG. 12.

[0142] The time response measurement device and the time response 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 may be combined with each other according to necessary purposes and effects.

Description of Reference Numerals

[0143] 1A, 1B, 1C... Time response measurement device, 2, 2A, 2B... Pulse laser light source, 3... Pulse formation unit, 3a... Light input end, 3b... Light output end, 4, 4A... Light attenuation unit, 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 plane, 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, 42... Wavelength filter, 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, 62... ROM, 64... Input device, 65... Output device, 66... Communication module, 67... Auxiliary storage device, 100... Device, 102... Sample, 501... Lens, 502... Long optical fiber, 503... Optical circulator, 504... Chirped fiber Bragg grating (CFBG), 505... Photodetector, AA, AB... Direction, B... Sample, D1, D2... Time interval, Lprobe... Probe light, Lpump... Pump light, P3, P4... Component pulse, P0, Pa... Pulse light, Pb... Light, Pc... Modulated light, PL... Pulse light, PL1... First pulse light, PL2... Second pulse light, PL3... Third pulse light, PLa, PLb... Pulse light, Pr... Reference pulse light, T1, T2, T3, T4... Peak intensity, TW1... First time waveform, TW2... Second time waveform, TW3... Third time waveform, TW4, TW5... Time waveform, W1, W2, W3, W4... Pulse width.

Claims

1. An apparatus for measuring the time response inside a sample due to light irradiation, comprising: a pulse forming unit that generates a first pulse light including the wavelength of pump light, a second pulse light including the wavelength of probe light, and a third pulse light including the wavelengths of the pump light and the probe light on a common optical axis; a light attenuation unit that allows the first pulse light, the second pulse light, and the third pulse light output from the sample after being irradiated to the sample disposed on the optical axis to pass therethrough, and having an attenuation rate for the pump light greater than that for the probe light; a waveform measuring unit that measures a first time waveform which is the time waveform of the first pulse light that has passed through the light attenuation unit, a second time waveform which is the time waveform of the second pulse light that has passed through the light attenuation unit, and a third time waveform which is the time waveform of the third pulse light that has passed through the light attenuation unit; an analysis unit that obtains the time response of the sample based on the first time waveform, the second time waveform, and the third time waveform; A time response measurement apparatus comprising the above components.

2. The time response measurement apparatus according to claim 1, wherein the analysis unit obtains the time response of the sample based on a comparison between a difference between the third time waveform and the first time waveform and the second time waveform.

3. The time response measurement apparatus according to claim 1 or 2, wherein the pulse forming unit has a spatial light modulator that simultaneously performs phase modulation and intensity modulation of the input pulse light to generate the first pulse light, the second pulse light, and the third pulse light.

4. The time response measurement apparatus according to any one of claims 1 to 3, wherein in the pulse forming unit, a time interval between an intensity peak of a component of the wavelength of the pump light included in the third pulse light and an intensity peak of a component of the wavelength of the probe light is variable.

5. The time response measurement apparatus according to any one of claims 1 to 3, wherein in the pulse forming unit, a ratio of a pulse width of a component of the wavelength of the pump light included in the third pulse light to a pulse width of a component of the wavelength of the probe light is variable.

6. The time response measurement apparatus according to any one of claims 1 to 5, 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.

7. The waveform measurement unit is disposed between the sample and the light attenuation unit or at a subsequent stage of the light attenuation unit, and has a correlation optical system that converts the first pulsed light, the second pulsed light, and the third pulsed light into correlation light including cross-correlation or auto-correlation. The analysis unit obtains the time response of the sample based on the first pulsed light, the second pulsed light, and the third pulsed light that have been converted into correlation light. The time response measurement device according to any one of claims 1 to 6.

8. The waveform measurement unit is disposed between the sample and the light attenuation unit or at a subsequent stage of the light attenuation unit, and has an optical component that extends the time widths of the first pulsed light, the second pulsed light, and the third pulsed light. The time response measurement device according to any one of claims 1 to 6.

9. The light attenuation unit has a wavelength filter that includes the wavelength of the pump light within a blocking band and includes the wavelength of the probe light within a transmission band. The time response measurement device according to any one of claims 1 to 8.

10. A method for measuring the time response inside a sample caused by light irradiation, irradiating the sample with a first pulsed light including the wavelength of the pump light along a predetermined optical axis, and measuring a first time waveform that is the time waveform of the first pulsed light that has passed through a light attenuation unit that attenuates the light intensity of the wavelength of the pump light after being output from the sample; irradiating the sample with a second pulsed light including the wavelength of the probe light along the predetermined optical axis, and measuring 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 sample; irradiating the sample with a third pulsed light including the wavelength of the pump light and the wavelength of the probe light along the predetermined optical axis, and measuring a third time waveform that is the time waveform of the third pulsed light that has passed through the light attenuation unit after being output from the sample; obtaining the time response of the sample based on the first time waveform, the second time waveform, and the third time waveform; The time response measurement method including.

11. In the step of obtaining the time response, the time response of the sample 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 time response measurement method according to claim 10.

12. In the step of measuring the first time waveform, the step of measuring the second time waveform, and the step of measuring the third time waveform, the first pulse light, the second pulse light, and the third pulse light are generated by using a spatial light modulator that simultaneously performs phase modulation and intensity modulation of the input pulsed light. The time response measurement method according to claim 10 or 11.

13. The time response measurement method according to any one of claims 10 to 12, wherein the pulse width of the component of the wavelength of the pump light included in the third pulse light is made smaller than the pulse width of the component of the wavelength of the probe light included in the third pulse light.

14. The time response measurement method according to any one of claims 10 to 13, wherein the step of measuring the third time waveform is performed after the step of measuring the first time waveform and the step of measuring the second time waveform.

Images