Broadband pulsed light source device, spectroscopic measuring device, spectroscopic measuring method, and spectroscopic analysis method

Abstract

[Problem] To provide a broadband pulsed light source device which has excellent performance, and which solves the problem of residual light in the wavelength region of seed light existing with a high intensity in supercontinuum light (SC light). [Solution] Supercontinuum light is generated by causing a non-linear effect to occur in light from a pulse laser source 1 by means of a non-linear element 2, and residual light at the oscillation wavelength of the pulse laser source 1 is attenuated when the supercontinuum light is split using a dichroic mirror 32. The split light beams are subjected to pulse extension by means of fibers 41, and are combined by means of a wave combining element 33, and the combined light beam is shone onto a target object S. Light that has been transmitted through the target object S is received by a light receiver 6, and an output signal therefrom is converted into a spectrum by a computing means 7.

Description

Technical Field

[0001] The invention of this application relates to a light source device that emits broadband pulsed light, and also relates to an apparatus and a method for performing spectroscopic measurement or analyzing an object using broadband pulsed light.

Background Art

[0002] A typical pulsed light source is a pulse-oscillating laser (pulsed laser). In recent years, research for broadening the wavelength band of pulsed lasers has been actively conducted, and a typical example thereof is generation of supercontinuum light (hereinafter referred to as SC light) using a nonlinear optical effect. SC light utilizes a nonlinear effect that occurs when high-intensity light interacts with a substance, and the nonlinear effect can be actively generated by increasing the photon density. For example, high-efficiency SC light generation is enabled by focusing light with high peak power, such as a pulsed laser, into a fiber having a core diameter of several μm and making the light incident thereon. Since the light propagates over a long distance in a state where the photon density is high due to the fiber, the nonlinear effect continuously occurs, and SC light with a broader band can be obtained. Main nonlinear effects in SC light generation are self-phase modulation, cross-phase modulation, Raman scattering, and four-wave mixing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] Such SC light is considered to be suitably usable for various applications due to its wide wavelength band. That is, applications utilizing its characteristics are expected not only in the field of optical communication such as wavelength division multiplexing communication, but also in the field of material analysis for investigating the wavelength dependency of materials, the field of image observation such as OCT and fluorescence microscopes, and the like.

[0005] In particular, broadband pulsed light (broadband stretched pulsed light) obtained by stretching the pulse width of SC light using a pulse stretching element is considered to be suitably usable in fields such as spectroscopic measurements. Although broadband pulsed light has a stretched wavelength range, its pulse width (time width) remains narrow. However, by utilizing the group delay in a transmission element such as a fiber, the pulse width can also be stretched. In this case, by selecting an element with appropriate wavelength dispersion characteristics, pulse stretching can be performed while maintaining a one-to-one correspondence between time (elapsed time) and wavelength within the pulse.

[0006] The correspondence between time and wavelength in broadband extended pulsed light, as described above, can be effectively utilized in spectroscopic measurements. When broadband extended pulsed light is received by a photodetector, the temporal change in light intensity detected by the photodetector corresponds to the light intensity at each wavelength, i.e., the spectrum. Therefore, the temporal change in the output signal of the photodetector can be converted into a spectrum, making spectroscopic measurements possible without the use of special dispersion elements such as diffraction gratings. In other words, by irradiating an object with broadband extended pulsed light, receiving the light from that object with a photodetector, and measuring its temporal change, the spectral characteristics of that object (e.g., spectral transmittance) can be determined.

[0007] Thus, SC light is expected to have applications in various fields. However, it also faces unique challenges. One of these is the problem of the strong peak of the pulsed laser light used in generating SC light. This point will be explained below with reference to Figure 15. Figure 15 is a conceptual diagram illustrating the challenges in SC light generation.

[0008] As mentioned above, SC light is a technology that generates light of new wavelengths through nonlinear optical effects such as self-phase modulation, four-wave mixing, and Raman scattering that occur when ultrashort pulsed light is incident on a nonlinear optical element, thereby generating broadband light. Most SC light sources currently on the market use ultrashort pulsed light in the picosecond to nanosecond range.

[0009] As shown in Figure 15(1), the original ultrashort pulse light (sometimes called seed light or seeder; hereafter referred to as seed light) is light with a very narrow bandwidth centered on the oscillation wavelength λs. However, when passed through a nonlinear element such as a nonlinear fiber, it becomes broadened as shown in Figure 15(2). In this case, although the bandwidth is broadened, the spectrum of the seed light often remains in the SC light spectrum as a ripple. For the sake of explanation, the wavelength width (full width at half maximum) where the intensity of the oscillation wavelength (peak wavelength) λs is half is defined as the oscillation wavelength range, and is shown as Rh in Figure 15(1).

[0010] The fact that the seed light spectrum remains rippled in this way can be a problem depending on the application field of SC light. When using only a specific wavelength from the broad bandwidth of SC light, and that wavelength is not included in the wavelength range of the seed light, it is often not a major problem. However, it can be a problem when it is necessary to irradiate with light of as uniform intensity as possible at each wavelength, such as when investigating the wavelength dependence of a material.

[0011] To give a more specific example, as mentioned earlier, when using pulsed SC light for spectroscopic measurements, variations in the intensity of the SC light spectrum significantly affect the dynamic range of the measurement. In other words, if there is a strong ripple in the seed light, the light will be captured by the photodetector with a wider dynamic range for the spectroscopic measurement. In this case, due to the finite number of bits in data processing, the intensity resolution in the measurement decreases proportionally to the wider dynamic range. This decrease in intensity resolution leads to a fundamental problem: a significant decrease in analytical accuracy or even inability to analyze, especially in analyses that require discerning slight differences in measurement values, such as material analysis in the near-infrared region.

[0012] The invention described in this application was made to solve the above-mentioned problems of broadband pulsed light sources that emit SC light, and aims to provide a broadband pulsed light source device with excellent performance that solves the problem of SC light remaining with high intensity in the wavelength range of the seed light, and to develop applied technologies using such a light source device. [Means for solving the problem]

[0013] To solve the above problems, the broadband pulsed light source device according to the invention of this application is characterized by comprising a pulsed laser source, a nonlinear element that generates a nonlinear effect on the light from the pulsed laser source and emits supercontinuous light, and an attenuation means that attenuates the light of the oscillation wavelength of the pulsed laser source contained in the supercontinuous light emitted from the nonlinear element. Furthermore, in order to solve the above problems, the broadband pulse light source device may be equipped with an extension element that extends the pulse width of the supercontinium light emitted from the nonlinear element so that the relationship between the wavelength of light and time within the pulse is one-to-one. Furthermore, to solve the above problems, the attenuation means may be a notch filter. Furthermore, to solve the above problems, the attenuation means may be a volume Bragg diffraction grating filter. Furthermore, to solve the above problems, the attenuation means may be a dichroic mirror, and the oscillation wavelength of the pulsed laser source may be within the divided wavelength range of this dichroic mirror. Furthermore, in order to solve the above problems, the broadband pulse light source device may have a configuration in which the attenuation means is a first and second dichroic mirror, the oscillation wavelength of the pulse laser source is within the divided wavelength range of these dichroic mirrors, and the second dichroic mirror is a multiplexing element that combines the light divided by the first dichroic mirror. Furthermore, in order to solve the above problems, the broadband pulsed light source device may be configured such that it includes a divider that spatially divides the supercontinuous light emitted from the nonlinear element into light of each wavelength range, and the attenuation means is a filter that attenuates the light of the pulse laser oscillation wavelength from among the light of each wavelength range divided by the divider. Furthermore, to solve the above problems, the divider may be an array waveguide diffraction grating. Furthermore, in order to solve the above problems, the attenuation means may be an array waveguide diffraction grating that spatially divides the supercontinuous light emitted from the nonlinear element into light in each wavelength range while the light at the oscillation wavelength of the pulsed laser source is attenuated. Furthermore, to solve the above problems, the oscillation wavelength of the pulsed laser source can be within the boundary wavelength range of the output waveguide of the array waveguide diffraction grating. Furthermore, in order to solve the above problems, the broadband pulse light source device may have a configuration in which the attenuation means is a dichroic mirror, the oscillation wavelength of the pulse laser source is within the divided wavelength range of the dichroic mirror, and the extension element consists of a first extension element that extends the pulse width of the light reflected by the dichroic mirror and a second extension element that extends the pulse width of the light transmitted through the dichroic mirror. Furthermore, in order to solve the above problems, the first and second extension elements may be fibers with different lengths or dispersion characteristics. Furthermore, in order to solve the above problems, the broadband pulse light source device may have a configuration in which the attenuation means is a dichroic mirror, the oscillation wavelength of the pulse laser source is within the divided wavelength range of this dichroic mirror, and this dichroic mirror is located on the output side of the extension element. Furthermore, in order to solve the above problems, the broadband pulsed light source device may be configured such that a divider spatially divides the supercontinuous light emitted from a nonlinear element into light of each wavelength range, the attenuation means is a filter that attenuates the light of the pulse laser oscillation wavelength from the light of each wavelength range divided by the divider, and the extension element is a plurality of fibers arranged in parallel on the output side of the divider, and each fiber is a fiber into which the light of each divided wavelength range is incident, and the fiber has different length or dispersion characteristics depending on the wavelength range of the incident light. Furthermore, in order to solve the above problems, the broadband pulsed light source device may have a configuration in which the attenuation means is an array waveguide diffraction grating that spatially divides the supercontinuous light emitted from the nonlinear element into light in each wavelength range while the light at the oscillation wavelength of the pulsed laser source is attenuated, and the extension element is a fiber connected to each output-side waveguide of the array waveguide diffraction grating, and each fiber has different lengths or dispersion characteristics depending on the wavelength range of the incident light.

[0014] Furthermore, in order to solve the above problems, the spectroscopic measuring device according to the invention of this application comprises a photodetector that receives light from an object irradiated with broadband pulsed light from the broadband pulsed light source device, and a calculation means that converts the output signal from the photodetector into a spectrum. Furthermore, in order to solve the above problems, the spectroscopic measuring device according to the invention of this application comprises a broadband pulse light source device, a photodetector that receives light from an object irradiated with broadband pulse light from the broadband pulse light source device, and a calculation means that converts the output signal from the photodetector into a spectrum. The attenuation means is a dichroic mirror, the oscillation wavelength of the pulse laser source is within the divided wavelength range of the dichroic mirror, and the photodetector is provided as a first photodetector into which light reflected from the dichroic mirror is incident, and a second photodetector into which light transmitted through the dichroic mirror is incident. Furthermore, in order to solve the above problems, the spectroscopic measurement method according to the invention of this application comprises a light receiving step of receiving light from an object irradiated with broadband pulsed light from the broadband pulsed light source device using a photodetector, and a conversion step of converting the output signal from the photodetector into a spectrum using a calculation means. Furthermore, in order to solve the above problems, the spectroscopic measurement method according to the invention of this application comprises a light receiving step in which light from an object irradiated with broadband pulsed light from the broadband pulsed light source device is received by a photodetector, and a conversion step in which the output signal from the photodetector is converted into a spectrum by a calculation means, the attenuation means is a dichroic mirror, the oscillation wavelength of the pulsed laser source is within the divided wavelength range of the dichroic mirror, and a first photodetector into which light reflected from the dichroic mirror is incident and a second photodetector into which light transmitted through the dichroic mirror is incident, the light receiving step is a step of receiving light with the first and second photodetectors, and the conversion step is a step of converting the output signals from each of the first and second photodetectors into a spectrum by a calculation means. Further, to solve the above problems, a spectral analysis method according to the invention of this application includes a light receiving step of receiving, with a light receiver, light from an object irradiated with broadband pulsed light from the broadband pulsed light source device, and a step of analyzing the object by processing an output signal from the light receiver with an arithmetic means and comparing the processed signal with a standard value, wherein the intensity width of supercontinuum light emitted from the broadband pulsed light source device is 3 dB or less.

Effects of the Invention

[0015] As described below, according to the broadband pulsed light source device of the invention of this application, the attenuating means attenuates the light at the oscillation wavelength of the pulse laser source, so that a spectrum with a flatter intensity distribution is obtained. Therefore, the broadband pulsed light source device that is suitably used for applications requiring SC light with more uniform intensity over a wide band is provided. Further, when the attenuating means is a notch filter, the above effects can be obtained at low cost with a simple configuration. Further, when the attenuating means is a volume Bragg diffraction grating filter, it is easy to realize selective attenuation in a narrower band, so that only the light at the oscillation wavelength of the pulse laser source can be accurately removed. Further, when the attenuating means is a dichroic mirror, selective attenuation is performed while wavelength-dividing the SC light, so that the SC light can be irradiated by making use of the division. Further, in the configuration provided with the stretching element, the pulse width is expanded in a state where the elapsed time within the pulse and the wavelength of light correspond one-to-one, so that SC light that is easier to handle is emitted. Further, in a configuration that includes a splitter and attenuates, with a filter, the light at the oscillation wavelength of the pulse laser among the light split by the splitter, pulse stretching can be easily optimized by transmitting the split light in each wavelength band through fibers having different lengths or dispersion characteristics to perform pulse stretching. Furthermore, when the arrayed waveguide diffraction grating is provided as an attenuation unit and has a function of performing selective attenuation, the number of components is reduced, which cuts costs and simplifies the structure. In this case, with a configuration where the oscillation wavelength of the pulsed laser source falls within the boundary wavelength band of the output-side waveguide of the arrayed waveguide, an effect is obtained that no new loss occurs in the arrayed waveguide diffraction grating due to attenuation. Furthermore, when spectroscopic measurement is performed using the broadband pulsed light source device that performs pulse stretching such that the elapsed time within a pulse and the wavelength of light are in a one-to-one correspondence, time-consuming operations such as sweeping of a diffraction grating are unnecessary, and high-speed spectroscopic measurement can be achieved. In particular, since the light at the oscillation wavelength of the pulsed laser source is selectively attenuated and spectroscopic measurement can be performed by irradiating broadband light with uniform spectral intensity, measurement results can be obtained without significantly expanding the dynamic range. Accordingly, a spectroscopic measurement apparatus and a spectroscopic measurement method with high intensity resolution are provided. Furthermore, in a configuration using a dichroic mirror as the attenuation unit, in which light of each divided wavelength band is received by a separate light receiver and the output signals thereof are converted into a spectrum, an appropriate light receiver can be selected and used according to the wavelength band, and spectroscopic measurement can be optimized in this respect. Then, in spectroscopic analysis in which the result of spectroscopic measurement is compared with a standard value, when the spectral intensity width is 3 dB or less, the problem that a slight difference in spectrum cannot be captured and measurement becomes impossible is sufficiently avoided. Brief Description of the Drawings

[0016] [Figure 1] It is a schematic diagram of the broadband pulsed light source device of the first embodiment. [Figure 2] It is a schematic diagram of the attenuation unit in the first embodiment. [Figure 3] It is a schematic diagram showing each type of volume Bragg diffraction grating filter that can be used as an attenuation unit. [Figure 4] It is a schematic diagram of the broadband pulsed light source device of the second embodiment. [Figure 5]This is a schematic diagram of the damping means in the second embodiment. [Figure 6] This is a schematic diagram of a broadband pulse light source device according to the third embodiment. [Figure 7] This is a schematic diagram of a broadband pulse light source device according to the fourth embodiment. [Figure 8] This is a schematic diagram illustrating pulse extension. [Figure 9] This is a schematic diagram of a broadband pulsed light source device according to the fifth embodiment. [Figure 10] This is a schematic diagram of the array waveguide diffraction grating used in the fifth embodiment. [Figure 11] This is a schematic diagram illustrating an example in which an array waveguide diffraction grating constitutes an attenuation mechanism. [Figure 12] This is a schematic diagram of the spectroscopic measuring apparatus according to the first embodiment. [Figure 13] This diagram schematically shows the main components of an example of a measurement program included in a spectroscopic measuring device. [Figure 14] This is a schematic diagram of the spectroscopic measurement apparatus according to the second embodiment. [Figure 15] This diagram conceptually illustrates the challenges in SC photogeneration. [Modes for carrying out the invention]

[0017] Next, I will describe embodiments for carrying out the invention of this application. First, an embodiment of the broadband pulsed light source device will be described. Figure 1 is a schematic diagram of the broadband pulsed light source device according to the first embodiment. This broadband pulsed light source device is a device that emits SC light. As shown in Figure 1, this device comprises a pulsed laser source 1, a nonlinear element 2 positioned at the location where light from the pulsed laser source 1 is incident, and attenuation means for selectively attenuating the SC light emitted from the nonlinear element 2.

[0018] As the pulsed laser source 1, an ultrashort pulse laser source is preferably used, such as a gain-switched laser, a microchip laser, or a fiber laser. For example, a fiber laser with an oscillation wavelength of 1064 nm and a pulse width of several picoseconds to several nanoseconds can be used as the pulsed laser source 1.

[0019] Fibers are often used as the nonlinear element 2. For example, photonic crystal fibers and other nonlinear fibers can be used as the nonlinear element 2. The fiber is usually single-mode, but even multimode fibers can be used as the nonlinear element 2 if they exhibit sufficient nonlinearity.

[0020] In this embodiment, a broadband pulsed light source device is assumed, which is provided for use in spectroscopic measurements in the 900-1300 nm range, as will be described later. Therefore, the SC light broadened by the nonlinear element 2 is light broadened in the 900-1300 nm range. There is no particularly established definition of what wavelength range of continuous spectrum can be called "supercontinuous," but for example, it can be said that if the spectrum is continuous for 30 nm or more, it can be said that if the spectrum is continuous for 50 nm or more, it can be said that the spectrum is continuous for at least 50 nm in any of the wavelengths in the 900-1300 nm range.

[0021] The attenuation means that characterizes the broadband pulse light source device of this embodiment is a means for attenuating light in the wavelength range of the seed light, that is, light at the oscillation wavelength of the pulse laser source 1. Several configurations of the attenuation means are possible, but in this embodiment, a notch filter 31 is used. The attenuation means in the first embodiment will be described with reference to Figure 2. Figure 2 is a schematic diagram of the attenuation means in the first embodiment. Of these, Figure 2(1) is a schematic diagram showing the spectrum of the SC light emitted in the first embodiment, and Figure 2(2) is a schematic diagram showing the spectral transmission characteristics of the notch filter used as the attenuation means.

[0022] As shown in Figure 2, the notch filter 31, as an attenuation means, selectively attenuates light at the oscillation wavelength of the pulsed laser source 1. The oscillation wavelength range Rh of the pulsed laser source 1 is defined, as mentioned above, for example, as the wavelength range of the full width at half maximum with respect to the peak wavelength (oscillation wavelength) λs. A more preferred characteristic of the notch filter 31 is that, as shown in Figure 2, the wavelength at which the transmittance is smallest (hereinafter referred to as the bottom wavelength) coincides with the oscillation wavelength λs of the pulsed laser source 1. However, it is not necessary for them to coincide exactly; it is sufficient that the bottom wavelength falls within the oscillation wavelength range Rh of the pulsed laser source 1. Furthermore, if we define the attenuation wavelength range as the wavelength range in which the attenuation rate is 50% or more of the maximum value (attenuation rate at the bottom wavelength) in the characteristics of the notch filter 31, then if the oscillation wavelength λs of the pulsed laser source 1 is within the attenuation wavelength range, the effect is sufficient and the implementation is feasible.

[0023] The extent to which the notch filter 31 attenuates light, that is, the magnitude of the transmittance at the bottom wavelength, depends on the intensity of the ripple in the light of the pulsed laser source 1 at its oscillation wavelength. For example, if the ripple intensity is about twice that of light of other wavelengths, the transmittance at the bottom wavelength is said to be about 50%, and the filter has the characteristic of selectively attenuating by about 50%.

[0024] Figure 2(3) schematically shows the spectrum of the SC light after it has passed through the notch filter 31, which is used as an attenuation means. As shown here, the spectrum of the SC light after passing through the notch filter has no ripple originating from the seed light and has a flatter spectral waveform. Therefore, a broadband pulse light source device is provided that is suitable for applications requiring SC light with a more uniform intensity over a wide bandwidth. In this embodiment, since the notch filter 31 is used as an attenuation means, the configuration is simple and the above effect can be obtained at a low cost. Furthermore, when reducing ripple originating from the seed light, it is not necessary for the intensity to decrease across the entire Rh oscillation wavelength range of pulsed laser source 1. It is sufficient for the intensity to decrease at least at the oscillation wavelength λs.

[0025] The notch filter 31 described above is often a filter element formed from a dielectric multilayer film. As an attenuation means, a volume Bragg grating filter can also be used. A volume Bragg grating (hereinafter referred to as a VBG filter) is a filter in which a fine region with periodically changing refractive index is fabricated within the optical element. By making the period of the refractive index change satisfy the Bragg condition, light of that wavelength can be selectively diffracted. In Japanese, VBG filters are sometimes written as volume Bragg grating, volume Bragg grating, or volume Bragg grating. Furthermore, because holographic technology is used to obtain the periodic refractive index change structure, or because the change structure is considered to correspond to a hologram, it is sometimes called a volume holographic diffraction grating.

[0026] Such VBG filters include transmissive and reflective types, and both can be used as attenuation means in the embodiments. In addition, chirp-type VBG filters (chirp VBG filters) that gradually change the period of low refractive index / high refractive index are also known. Chirp-type filters can also be used as attenuation means in the embodiments. Figure 3 is a schematic diagram showing each type of VBG filter that can be used as an attenuation means.

[0027] Figure 3(1) shows an example using a transmissive VBG filter 351. In a transmissive VBG filter 351, only light of a specific wavelength λc is refracted in a specific direction according to the period of refractive index change, while light of other wavelengths is transmitted as is. Therefore, by selecting the oscillation wavelength λs of the pulsed laser source 1 as λc, it can be suitably used as an attenuation means. Figure 3(2) shows an example using a reflective VBG filter 352. In the case of a reflective filter, only light of a specific wavelength λc is reflected in a specific direction depending on the period of refractive index change, while light of other wavelengths is transmitted as is.

[0028] Figures 3(3) and 3(4) show examples of using chirp VBG filters 353 and 354. Figure 3(3) is a transmissive type, and Figure 3(4) is a reflective type. In chirp VBG filters 353 and 354, the period of the refractive index change is further periodically changed, so light within the wavelength range corresponding to the changing range is selectively extracted. That is, in the transmissive chirp VBG filter 353 in Figure 3(3), only light within a certain wavelength range (λc1 to λc2) is refracted and extracted. In the reflective chirp VBG filter 354 in Figure 3(4), only light between λc1 and λc2 is reflected and extracted.

[0029] In Figures 3(1) to (4), light other than λc, λc1 to λc2, which are selectively refracted or reflected, travels along the original optical path (main optical path). Light from λc, λc1 to λc2 travels along an optical path that deviates from the main optical path, and in many cases, a beam damper or similar device is placed here to perform termination processing to absorb the light. However, if there is no particular problem, the light may be left as is without actively absorbing it. In addition, VBG filters 351 to 354 are often positioned so that the light is incident at an angle to prevent backlighting, and are often at an angle to the main optical path.

[0030] Such VBG filters 351-354 are preferable to dielectric multilayer notch filters because they can narrow the attenuation wavelength range. In the case of dielectric multilayer notch filters, the attenuation wavelength range may be slightly wider than the full width at half maximum of the ripple (peak originating from the seed light) in SC light, and in this case, light of wavelengths that should not be attenuated may be attenuated. VBG filters have the advantage of easily achieving narrow-band selective attenuation of about the full width at half maximum of the ripple, and can accurately remove only the ripple.

[0031] Furthermore, among the VBG filters, the standard VBG filters 351 and 352 are used for applications such as laser wavelength stabilization, and are capable of selective attenuation in a particularly narrow bandwidth. Therefore, when the full width at half maximum (FWHM) of the ripple in SC light is particularly narrow, the standard VBG filters 351 and 352 are preferably used. When the FWHM of the ripple is not that narrow, but is narrower than the attenuation wavelength range of a dielectric multilayer notch filter, the chirp VBG filters 353 and 354 are preferably used. For example, if the full width at half maximum (FWHM) of the ripple in SC light is 40 nm or more, a dielectric multilayer notch filter can be used. However, if the FWHM is narrower, up to about 2 nm, chirp VBG filters 353 and 354 are preferably used. If the FWHM is 2 nm or less, then ordinary VBG filters 351 and 352 are preferably used.

[0032] These VBG filters 351, 352 and chirp VBG filters 353, 354 are available from companies such as OptiGrate Corp. (562 South Econ Circle Oviedo, Florida 32765-4311) in the United States, and custom orders specifying the wavelength to be extracted or the wavelength band are also possible. VBG filters are sometimes referred to as Bragg-Grate notch filters and are sometimes considered a type of notch filter.

[0033] Next, a broadband pulse light source device of the second embodiment will be described. Figure 4 is a schematic diagram of the broadband pulse light source device of the second embodiment. In the second embodiment, a dichroic mirror 32 is used as the attenuation means. Figure 5 is a schematic diagram of the attenuation means in the second embodiment. Of these, Figure 5(1) is a schematic diagram showing the spectrum of the emitted SC light, and Figure 5(2) is a diagram schematically showing the spectral reflectance / transmission characteristics of the dichroic mirror used as the attenuation means. In Figure 5(2), the solid line shows the spectral reflectance characteristics, and the dashed line shows the spectral transmission characteristics.

[0034] A dichroic mirror is an optical element that splits light at a dividing wavelength, transmitting light from one wavelength range and reflecting light from the other. In reality, the transition between transmission and reflection occurs over a certain wavelength range, which is referred to as the dividing wavelength range. In the following example, the overlapping area between the wavelength range where the transmittance is 80% or less of the peak (maximum value) and the wavelength range where the reflectance is 80% or less of the peak is defined as the "dividing wavelength range." As shown in Figure 5, in this embodiment, the oscillation wavelength of the pulsed laser source 1 is within the dividing wavelength range. The wavelength at which the transmission and reflection characteristics intersect (the wavelength at which the transmittance and reflectance are equal) is specifically called the dividing wavelength. The dividing wavelength is usually in the center of the dividing wavelength range. As shown in Figure 4, in this embodiment, a multiplexing element 33 is provided that superimposes the light separated by the dichroic mirror 32. In this example, the multiplexing element 33 is a dichroic mirror. The multiplexing element 33 is a dichroic mirror that reflects light with wavelengths longer than the divided wavelength range and transmits light with wavelengths shorter than the divided wavelength range. Although the reflection / transmission is reversed, the divided wavelength range here almost coincides with the divided wavelength range in the dichroic mirror 32.

[0035] Figure 5(3) shows the spectrum of the SC light after superimposition by the multiplexing element 33. The spectral reflectance / transmission characteristics of the dichroic mirror 32 as an attenuation means are appropriately selected so that the spectral intensity of the emitted SC light is flat. In this example, a dichroic mirror is also used as the multiplexing element 33, so the attenuation there is also taken into consideration. For example, as mentioned above, if the overall attenuation rate is to be about 50%, as shown in Figure 5(2), the spectral reflectance / transmission characteristics of the dichroic mirror 32 as an attenuation means are set to approximately 50% for both transmission and reflection at the divided wavelength. That is, about 50% of the light at the oscillation wavelength of the pulsed laser source 1 is reflected and about 50% is transmitted by the dichroic mirror 32. In this case, the dichroic mirror as the multiplexing element 33 reflects and transmits at approximately 50% at the divided wavelength. In this way, if the oscillation wavelength λs of the Hals laser source 1 is equal to the divided wavelength, the light at the oscillation wavelength λs is ultimately attenuated to about 50%. Therefore, the spectrum of the emitted SC light has a flat intensity distribution overall, as shown in Figure 5(3). As can be seen from the above explanation, in this example, the two dichroic mirrors 32 and 33 serve as attenuation means.

[0036] In a configuration using the dichroic mirror 32 as an attenuation means, selective attenuation is performed while wavelength-splitting the SC light, allowing for SC light irradiation that takes advantage of the splitting. For example, this configuration is convenient when it is necessary to irradiate an object with light divided into two wavelength ranges, or when it is necessary to irradiate light in different wavelength ranges under different conditions. Furthermore, the oscillation wavelength λs of the pulsed laser source 1 does not necessarily have to match the splitting wavelength; sufficient effect can be obtained as long as it is within the splitting wavelength range. Defining the splitting wavelength range as 70% or less, rather than 80% or less, is preferable because it is more likely to result in attenuation, and 60% or less is even preferable.

[0037] Next, the third and fourth embodiments will be described. Figure 6 is a schematic diagram of the broadband pulsed light source device of the third embodiment, and Figure 7 is a schematic diagram of the broadband pulsed light source device of the fourth embodiment. As shown in Figures 6 and 7, these broadband pulse light source devices are equipped with a pulse extension element 4 that extends the pulse width of the supercontinuous light emitted from the nonlinear element 2. The third embodiment shown in Figure 6 is an embodiment in which the pulse extension element 4 is added to the first embodiment, and the fourth embodiment shown in Figure 7 is an embodiment in which the pulse extension element 4 is added to the second embodiment. The pulse extension element 4 will be described below. Figure 8 is a schematic diagram showing pulse extension.

[0038] The generated SC light has a broadened wavelength band, but its pulse width remains on the order of femtoseconds or picoseconds, making it difficult to use in certain applications. Therefore, pulse extension is performed. As the extension element 4, a configuration utilizing a fiber with specific group delay characteristics, such as a dispersion-compensated fiber (DCF), can be adopted. For example, if SC light L1, which has a continuous spectrum in a certain wavelength range, is passed through a group delay fiber 41 having positive dispersion characteristics in that wavelength range, the pulse width is effectively extended. That is, as shown in Figure 8, in SC light L1, although it is an ultrashort pulse, the longest wavelength λ1 light is present at the beginning of one pulse, and as time progresses, light with gradually shorter wavelengths is present, and at the end of the pulse, the shortest wavelength λ nLight exists. When this light is passed through a group delay fiber 41 with normal dispersion, shorter wavelength light propagates more slowly in a group delay fiber 41 with normal dispersion, so the time difference within one pulse is increased, and when the light exits the fiber 41, the shorter wavelength light is even more delayed than the longer wavelength light. As a result, the emitted SC light L2 becomes light with an extended pulse width while ensuring uniqueness between time and wavelength. That is, as shown in the lower part of Figure 8, from time t1 to t n The wavelengths are λ1 to λ n Each element is pulsed in a one-to-one correspondence.

[0039] Furthermore, an anomalous dispersion fiber can also be used as the fiber 41 for pulse extension. In this case, the longer wavelength light present at the beginning of the pulse lags behind the shorter wavelength light present at later times, causing the temporal relationship within a single pulse to reverse. As a result, the pulse is extended with shorter wavelength light present at the beginning and longer wavelength light present as time progresses. However, compared to the normal dispersion case, a longer propagation distance is often required for pulse extension, which tends to increase losses. Therefore, normal dispersion is preferable in this respect.

[0040] Thus, according to the broadband pulse light source devices of the third and fourth embodiments, broadband pulsed light is emitted with a broadened wavelength range as well as a widened pulse width, making it usable for various purposes. In particular, in these embodiments, the elapsed time within the pulse and the wavelength of the light correspond one-to-one, resulting in the emission of broadband pulsed light that is easier to handle.

[0041] Next, a broadband pulsed light source device of the fifth embodiment will be described. Figure 9 is a schematic diagram of the broadband pulsed light source device of the fifth embodiment. The broadband pulse light source device of the fifth embodiment also includes an extension element 4. In this embodiment, a divider is provided that spatially divides the SC light emitted from the nonlinear element 2 into light in each wavelength range. In this embodiment, an array waveguide grating (AWG) 51 is used as the divider.

[0042] Figure 10 is a schematic diagram of an array waveguide diffraction grating used in the fifth embodiment. As shown in Figure 10, the array waveguide diffraction grating 51 is constructed by forming functional waveguides 512 to 516 on a substrate 511. Each functional waveguide consists of a number of grating waveguides 512 with slightly different optical path lengths, slab waveguides 513 and 514 connected to both ends (incident and exit sides) of the grating waveguides 512, an incident waveguide 515 that causes light to be incident on the incident slab waveguide 513, and exit waveguides 516 that extract light of each wavelength from the exit slab waveguide 514.

[0043] The slab waveguides 513 and 514 are free space, and light incident through the incident waveguide 515 spreads out in the incident slab waveguide 513 and is incident on each grating waveguide 512. Since each grating waveguide 512 is slightly different in length, the light that reaches the end of each grating waveguide 512 is phase-shifted by this difference. Light is diffracted and emitted from each grating waveguide 512, and the diffracted light interferes with each other as it passes through the exit slab waveguide 514 and reaches the incident end of the exit waveguide 516. At this time, due to interference and phase shift, particularly strong light appears at the incident end of the exit waveguide 516 at a position corresponding to the wavelength. In other words, light of sequentially different wavelengths is incident on each exit waveguide 516, and the light is spatially spectrally separated. Each exit waveguide 516 is formed so that each incident end is located at the position where the light is spectrally separated.

[0044] Such array waveguide diffraction gratings 51 can be fabricated, for example, by surface-treating a silicon substrate 511. Specifically, a cladding layer (SiO2 layer) is formed on the surface of the silicon substrate 511 by flame deposition, and a core SiO2-GeO2 layer is similarly formed by flame deposition. Then, the SiO2-GeO2 layer is patterned by photolithography to form the waveguides 512 to 516. The line width of each grating waveguide 512 can be, for example, about 5 to 6 μm. The number of output waveguides 516 formed depends on the wavelength range of the broadband pulsed light. For example, when used with light that has a continuous spectrum over a wavelength range of approximately 900 to 1700 nm, the number of output waveguides 516 is about 10 to 100, and the light is split into wavelengths of 3 to 60 nm apart before being emitted.

[0045] In this embodiment as well, a fiber 42 is used as the extension element 4. In this embodiment, multiple fibers 42 are provided as extension elements 4 and are connected to each output-side waveguide 516 of the array waveguide diffraction grating 51. Each fiber 42 may be the same (made of the same material and structure) and the same length, but it is preferable to use different fibers or to use the same fiber but with different lengths. In this embodiment, each fiber 42 transmits light in each wavelength range divided by the divider, and pulse extension occurs at that time, so pulse extension can be optimized by using fibers with characteristics and lengths corresponding to the wavelength range. As mentioned above, pulse extension utilizes group velocity dispersion in the fiber, so the characteristic here is the dispersion characteristic.

[0046] For example, even with the same fiber, it is preferable to use fibers of different lengths depending on the wavelength range. Since the amount of group delay in a fiber depends on the length of the fiber, by using fibers of appropriate lengths according to the wavelength range, the group delay in each wavelength range can be made appropriate, thereby achieving optimal pulse extension. For example, even when using a fiber with normal dispersion characteristics within a certain wavelength range, the absolute value of the dispersion value (negative value) differs depending on the wavelength, so the slope of time versus wavelength (Δλ / Δt in Figure 8) of the light emitted from the fiber (light after pulse extension) is not uniform. In this case, by appropriately selecting the length of each fiber 42 in the above configuration, Δλ / Δt can be made more uniform. In addition to changing the length of the fiber 42, fibers with different dispersion characteristics may also be used. That is, it is preferable to connect and use fibers 42 having appropriate dispersion characteristics according to the wavelength of light emitted from each output-side waveguide 516.

[0047] As shown in Figures 9 and 10, in this embodiment, multiplexing elements 52 are provided on the output side of the multiple fibers 42 that serve as the extension element 4. The multiplexing element 52 is an element that superimposes the light emitted from each fiber 42 and emits it as a single light beam from the device. For example, a fan-in / fan-out device is preferably used as the multiplexing element 52. As fan-in / fan-out devices, fiber melting type and spatial type are known, and any of them may be used.

[0048] In this fifth embodiment, the attenuation means selectively attenuates the light of the pulse laser source 1 at its oscillation wavelength from the light emitted by the array waveguide diffraction grating 51 acting as a divider. Specifically, as shown in Figure 10, a dimming filter 34 is provided between the fiber 42 corresponding to the output-side waveguide 516 of the array waveguide diffraction grating 51 that emits light of the pulse laser source 1 at its oscillation wavelength. The dimming filter 34 may be an ND filter, a notch filter, or a VBG filter that selectively attenuates light of the pulse laser source 1 at its oscillation wavelength. In this way, as in the embodiments described above, SC light with an intensity-flat spectral distribution is emitted. The dimming filter 34 may also be provided between the fiber 42 that transmits light of the pulse laser source 1 at its oscillation wavelength and the multiplexing element 52.

[0049] In addition to using the attenuation filter 34, it is also possible to incorporate a selective attenuation function into the configuration of the array waveguide diffraction grating itself. This point will be explained with reference to Figure 11. Figure 11 is a schematic diagram showing an example in which the array waveguide diffraction grating constitutes an attenuation means. There are several possible examples in which the array waveguide grating itself constitutes an attenuation mechanism, but one preferred example is to design and fabricate the array waveguide grating such that the oscillation wavelength of the pulsed laser source 1 falls within a single boundary wavelength range in the output-side slab waveguide of the array waveguide grating. Figure 11 shows this example. The boundary wavelength range is the region in which the coupling intensity is, for example, 80% or less of the peak.

[0050] In the array waveguide diffraction grating 51, as described above, a phase difference is given in the grating waveguide 512, and the diffracted light in the exit-side slab waveguide 514 appears strongly at sequentially different positions depending on the wavelength due to the phase difference and interference. The incident end of the exit-side waveguide 516 is positioned at each of the positions where the intensity increases. Hereinafter, the intensity of the light in the exit-side waveguide 516 will be called the coupling intensity. The position at which the coupling intensity of the diffracted light of which wavelength is strongest is determined by the design of the optical path length difference of each grating waveguide 512 and the design of the exit-side slab waveguide 514, etc. That is, as shown in Figure 11, λ1, λ2, λ3, ...λ n The light from each position has a high coupling strength. In this case, λ1, λ2, λ3, ...λ n The oscillation wavelength of pulsed laser source 1 is positioned within the boundary wavelength range of any of the wavelengths. In this way, the SC light is spatially wavelength-divided while the light of the oscillation wavelength is effectively attenuated.

[0051] In the above configuration, λ1, λ2, λ3, ...λ n δλ in this context corresponds to the wavelength resolution in the array waveguide grating 51, but the boundary wavelength range is slightly narrower than the width of δλ. As an example of a suitable design, as shown in Figure 11, the wavelength at the center of one boundary wavelength range is matched to the oscillation wavelength λs of the pulsed laser source 1.

[0052] Thus, by enabling selective attenuation as a function of the array waveguide diffraction grating 51 itself, a light-reducing filter becomes unnecessary, resulting in structural simplification and cost reduction. In the example above, the oscillation wavelength λs of the pulsed laser source 1 was in the center of the boundary wavelength range, but the effect can be obtained if it is within the boundary wavelength range. Furthermore, defining the boundary wavelength range as 60% or less instead of 80% or less is preferable as it provides greater attenuation, and 40% or less is even preferable. In addition to the above configuration, the oscillation wavelength of the pulsed laser source 1 may be located within one of the wavelength ranges divided by the array waveguide diffraction grating 51, and a region that attenuates light may be provided in the waveguide (for example, the corresponding grating waveguide 512) in that wavelength range. However, in this configuration, one of the wavelength ranges divided by the array waveguide diffraction grating 51 is attenuated as a whole, resulting in new losses. The configuration in which the oscillation wavelength of the pulsed laser source 1 is located within one boundary wavelength range does not result in new losses and is therefore preferable.

[0053] In the fifth embodiment, as constituting the extension element 4, each output-side waveguide 516 is connected to a fiber 42, and pulse extension is performed so that there is a one-to-one correspondence between time and wavelength. Each fiber 42 has characteristics and / or length appropriate to the wavelength range to be transmitted, and pulse extension is optimized.

[0054] Next, embodiments of the spectroscopic measurement device and spectroscopic measurement method will be described. Figure 12 is a schematic diagram of the spectroscopic measurement device of the first embodiment. The spectroscopic measurement device shown in Figure 12 comprises a broadband pulse light source device 10, an irradiation optical system 100 that irradiates an object S with broadband pulse light emitted from the broadband pulse light source device 10, a photodetector 6 positioned at the location where light from the irradiated object S enters, and a calculation means 7 that calculates the spectral spectrum of the object S according to the output from the photodetector 6.

[0055] In this embodiment, the broadband pulsed light source device (hereinafter simply referred to as the light source device) 10 is the fourth embodiment equipped with an extension element 4, but the third or fifth embodiment may also be used. In this embodiment, the irradiation optical system 100 includes a beam expander 101. The light from the light source device 10 is time-extended broadband pulsed light, but it is light from the pulsed laser source 1, and this takes into account the small beam diameter. In addition, a scanning mechanism such as a galvanometer mirror may be provided to cover a wide irradiation area by beam scanning.

[0056] The photodetector 6 is one that converts the intensity of the received light into an electrical signal and outputs that signal. Specifically, a photodetector such as a photodiode with sensitivity in the measurement wavelength range is used. In this embodiment, it is assumed that the absorption spectrum of the object S is to be measured, and therefore the photodetector 6 is placed at a position where transmitted light from the object S is incident. A transparent receiving plate 8 is provided to hold the object S. The illumination optical system 100 is configured to emit light from above, and the photodetector 6 is positioned below the receiving plate 8.

[0057] In this embodiment, a general-purpose PC is used as the calculation means 7. An AD converter 61 is provided between the light receiver 6 and the calculation means 7, and the output of the light receiver 6 is input to the calculation means 7 via the AD converter 61. The calculation means 7 includes a processor 71 and a storage unit (hard disk, memory, etc.) 72. The storage unit 72 has a measurement program 73 installed that converts the output signal from the photodetector 6 into a spectrum, and other necessary programs.

[0058] In this embodiment, a light source device 10 that emits broadband extended pulsed light with unique time and wavelength is used, and the measurement program 73 is optimized accordingly. Figure 13 is a schematic diagram showing the main parts of an example of a measurement program 73 provided in a spectroscopic measurement device.

[0059] The example in Figure 13 shows that the measurement program 73 measures an absorption spectrum (spectral absorptivity). Reference spectral data is used when calculating the absorption spectrum. Reference spectral data are wavelength-specific values ​​that serve as a reference for calculating the absorption spectrum. Reference spectral data is acquired by directing light from the light source device 10 into the photodetector 6 without passing through the object S. That is, light is directly incident on the photodetector 6 without passing through the object S, and the output of the photodetector 6 is input to the calculation means 7 via the AD converter 61 to acquire values ​​for each time resolution Δt. Each value is stored as the reference intensity for each time t1, t2, t3, ... for each Δt (V1, V2, V3, ...). The time resolution Δt is a quantity determined by the response speed (signal output period) of the photodetector 6, and means the time interval at which the signal is output.

[0060] The reference intensities V1, V2, V3, ... at each time t1, t2, t3, ... are the intensities (spectrums) of the corresponding wavelengths λ1, λ2, λ3, .... The relationship between time t1, t2, t3, ... and wavelength within a single pulse has been investigated in advance, and the values ​​V1, V2, V3, ... at each time are treated as the values ​​of λ1, λ2, λ3, .... Then, when the light that has passed through the object S is incident on the photodetector 6, the output from the photodetector 6 is similarly stored in memory as values ​​(measured values) at each time t1, t2, t3, ... via the AD converter 61 (v1, v2, v3, ...). Each measured value is compared with the reference spectral data (v1 / V1, v2 / V2, v3 / V3, ...), and the result is the absorption spectrum (strictly speaking, each value is obtained by taking the logarithm of the reciprocal). The measurement program 73 is programmed to perform the above calculations.

[0061] Next, the operation of the spectroscopic measuring device described above will be explained. The following explanation also describes an embodiment of the spectroscopic measuring method. When performing spectroscopic measurement using the spectroscopic measuring device of this embodiment, the light source device 10 is operated without the object S in place, and light that has not passed through the object S is directly incident on the photodetector 6, and the output signal from the photodetector 6 is processed to obtain reference spectral data in advance. Then, the object S is placed on the receiving plate 6, and the light source device 10 is operated again. Then, the light that has passed through the object S is incident on the photodetector 6, and the output signal from the photodetector 6 is input to the calculation means 7 via the AD converter 61, and the spectrum is obtained by the measurement program 73.

[0062] In the example above, the absorption spectrum was measured using transmitted light from the object S. However, it is also possible to measure the reflectance spectrum (spectral reflectance) using reflected light from the object S, or to measure spectral characteristics such as internal scattered light from the object S. In other words, the light from the object S can be transmitted light, reflected light, or scattered light from the illuminated object S. Furthermore, if the measurements of the light source device 10 or the sensitivity characteristics of the photodetector 6 change over time, a calibration procedure is periodically performed to update the reference spectrum by taking measurements to acquire a reference spectrum (measurements taken without the object S in place).

[0063] According to the spectroscopic measurement apparatus and spectroscopic measurement method of this embodiment, the pulse width of broadband pulsed light from the pulsed light source 1 is extended so that the relationship between the elapsed time and wavelength within one pulse is one-to-one, and the object S is irradiated with this extended pulse for spectroscopic measurement. Therefore, time-consuming operations such as sweeping of a diffraction grating are unnecessary, and high-speed spectroscopic measurement can be performed. In particular, since the light at the oscillation wavelength of the pulsed laser source 1 is selectively attenuated, and spectroscopic measurements can be performed by irradiating broadband light with uniform spectral intensity, measurement results can be obtained without significantly widening the dynamic range. Therefore, a spectroscopic measurement device with high intensity resolution is provided.

[0064] The points mentioned above are particularly evident in applications where material analysis is performed based on subtle differences in spectra. This point will be explained further with more specific analytical examples. A more specific example of the spectroscopic measurement method described above is near-infrared spectroscopy. Near-infrared spectroscopy is a technique that quantifies materials based on slight differences in absorption spectra. Since various factors influence the absorption of light in the near-infrared region, resulting in many variables, chemometrics (multivariate analysis) methods are often employed. In this type of spectroscopic analysis, similar spectroscopic measurements are performed on numerous samples with known amounts of the target component to obtain absorption spectra, and regression analysis (such as PLS regression) is performed on the numerous measurement results to determine the regression coefficients. Then, similar spectroscopic measurements are performed on an unknown sample (target object), and the regression coefficients are applied to the obtained absorption spectrum to quantify the target component.

[0065] When performing such spectroscopic analysis, a wide dynamic range leads to a decrease in intensity resolution due to the limitations of the number of bits in data processing. A decrease in intensity resolution makes it impossible to capture slight differences in absorption spectra, rendering the analysis impossible. However, by using the broadband pulsed light source device of the embodiment described above, the dynamic range is reduced, allowing for the capture of slight differences in absorption spectra and enabling quantitative analysis. In spectroscopic analysis performed by comparing the values ​​obtained from such spectroscopic measurements with a reference value, the above problem does not occur if the spectral intensity width of the SC light is set to, for example, 3 dB or less. Note that 3 dB or less may apply to the entire wavelength range of the light output from the broadband pulsed light source device, but even if it does not apply to the entire wavelength range, it is sufficient if it is 3 dB or less in the wavelength range used for analysis, and such light source devices may be used. For example, the spectral intensity width may be set to 3 dB or less in the wavelength range of 900 to 1300 nm, or it may be set to 3 dB or less in a wavelength range of 30 nm or more, 50 nm or more, or 100 nm or more within the 900 to 1300 nm wavelength range.

[0066] Next, a spectroscopic measuring apparatus and spectroscopic measuring method of the second embodiment will be described. Figure 14 is a schematic diagram of the spectroscopic measuring apparatus of the second embodiment. The spectroscopic measuring device of the second embodiment, like the first embodiment, is equipped with a light source device 10 that includes a dichroic mirror 32 as an attenuation means. The difference between the spectroscopic measuring device of the second embodiment and the first embodiment is that there is no multiplexing element, and the light from each wavelength range after division by the dichroic mirror 32 is irradiated onto the object S, and the light from the object S irradiated with light of each wavelength range is received by separate photodetectors 601 and 602.

[0067] In this example, receiving plates 8 are provided on each of the two optical paths on the output side of the dichroic mirror 32, and photodetectors 601 and 602 are positioned on the receiving plates 8 at locations that receive light transmitted through the object S. For example, if the dichroic mirror 32 has the characteristic of transmitting wavelengths longer than the splitting wavelength and reflecting shorter wavelengths, the light on the longer wavelength side is received by the first photodetector 601, and the light on the shorter wavelength side is received by the second photodetector 602. In addition, a fiber 41 is provided as an extension element 4 in each optical path, as in the fourth embodiment. In this configuration as well, the oscillation wavelength of the pulsed laser source 11 is within the divided wavelength range of the dichroic mirror 32. The calculation means 7 converts the output signal from the first photodetector 601 to obtain a spectrum in the wavelength range longer than the divided wavelength, and converts the output signal from the second photodetector 602 to obtain a spectrum in the wavelength range shorter than the divided wavelength. For the divided wavelength, the output signal from either photodetector 601 or 602 is converted to obtain the spectrum. For example, if the seed light has twice the spectral intensity, and the reflectance and transmittance are set to 50%, then the light will be incident on either photodetector 601 or 602 at a 50% reduction, so the measurement system as a whole can be measured without being affected by the ripple of the seed light.

[0068] In this configuration, where the light divided by the dichroic mirror 32 is received by separate photodetectors 601 and 602, it is possible to use appropriate photodetectors depending on the wavelength range, thereby optimizing the spectroscopic measurement. The above points are closely related to the adoption of the light source device 10 that emits SC light. The light source device 10, which is an SC light source, can emit pulsed light with a wider bandwidth, but on the other hand, it is difficult to cover a wide bandwidth with a single photodetector. For example, when performing spectroscopic measurements in the near-infrared region, an InGaAs diode photodetector using InGaAs as the photodetector cell can be suitably used. However, when attempting to perform spectroscopic measurements over a wide bandwidth from the visible region to the near-infrared region, the InGaAs diode photodetector does not have sufficient sensitivity in the short wavelength range of less than 900 nm. An example of a photodetector that has sufficient sensitivity in the wavelength range of less than 900 nm is a Si diode photodetector that uses a Si photodiode as the photodetector cell. Therefore, using an InGaAs photodetector and a Si diode photodetector as the first and second photodetectors 601 and 602 is an extremely suitable configuration for spectroscopic measurements that cover a wider wavelength range from the visible to the near-infrared region. To give examples of other photodetectors, for instance, a CdS photodetector can be used in the visible range, while a PbS photodetector or InSb photodetector can be used in the near-infrared range.

[0069] In the embodiment shown in Figure 14, since receiving plates 8 are provided on each optical path, the spectroscopic measurement configuration involves sequentially placing one object S on the receiving plate 8, performing spectroscopic measurements in each wavelength range, and integrating these results to obtain spectroscopic measurement results for all wavelengths. In some cases, a single receiving plate 8 may be used, and switching may be performed using a shutter or the like. The branched optical paths are superimposed again using a dichroic mirror or the like, and the receiving plate is placed there. The shutter is used to switch so that light of each wavelength range is sequentially irradiated onto the object on the receiving plate. The photodetector is also switched along with the shutter switching, and spectroscopic measurements are performed sequentially in each wavelength range.

[0070] Furthermore, although a detailed explanation will be omitted, the configuration of employing separate photodetectors for each wavelength range can also be used in configurations that use dividers that finely divide wavelengths, such as array waveguide diffraction gratings. For example, when employing the aforementioned array waveguide diffraction grating 51, each fiber 42 connected to the output waveguide 516 is divided into two groups according to wavelength, and each group is combined with a multiplexing element and irradiated onto the target object S. Then, the light from the target object S irradiated with light from the long-wavelength group is received by one photodetector, and the light from the target object S irradiated with light from the short-wavelength group is received by the other photodetector. Furthermore, in both the case of using a dichroic mirror 32 and the case of using a divider such as an array waveguide diffraction grating 51, there may be three or more photodetector bands. That is, it may be possible to use three or more photodetectors to perform photoelectric conversion according to the band.

[0071] Furthermore, in the configurations of each embodiment using dividers such as a dichroic mirror 32 or an array waveguide diffraction grating 51, if an extension element 4 is provided, the extension element 4 may be positioned on the incident side of the dichroic mirror 32 or divider. That is, it may be a configuration in which pulse extension is performed first, followed by division by the dichroic mirror 32 or divider. However, in the case of a configuration in which division is performed by the dichroic mirror 32 or divider first, and then pulse extension is performed, as described above, a pulse extension configuration corresponding to the wavelength range can be adopted, and also, since sharp ripples of the oscillation wavelength of the pulse laser source 1 do not incident on the extension element 4, it is also preferable in terms of protecting the extension element 4.

[0072] Furthermore, the selective attenuation of light at the oscillation wavelength of the pulsed laser source 1 is a matter of dynamic range in measurement, so attenuation only needs to occur at any point in the optical path between the nonlinear element 2 and the photodetector 6, and in some cases, attenuation means may be provided between the object S and the photodetector 6. However, in terms of protecting the object S from sharp ripples originating from the seed light, it is preferable that the attenuation means be provided in the optical path before the object S.

[0073] Furthermore, the term "attenuation" by attenuation means has a broad meaning and is not limited to cases where light is absorbed by an element and its intensity weakens. The purpose is to prevent the dynamic range in the photodetector from widening, so it also includes cases where a portion of the light at the oscillation wavelength of the pulsed laser source is reflected or scattered and excluded from the optical path, resulting in a decrease in the intensity when incident on the photodetector.

[0074] Furthermore, in the configuration of the spectroscopic measurement device and spectroscopic measurement method described above, a configuration may be adopted in which the light from the light source device 10 is split into measurement and reference beams using a beam splitter or the like, the light that has passed through the object S is detected by a photodetector 6, and a reference photodetector is provided to receive the light directly without passing through the object S. In this configuration, reference spectral data is acquired in real time, eliminating the need for separate calibration work and offering the advantage of increased measurement efficiency.

[0075] In addition to the spectroscopic measurements and analyses mentioned above, broadband pulsed light sources can be used for a variety of other applications. For example, they can be used for imaging and observing objects, such as in optical coherence tomography (OCT) and fluorescence microscopy. Furthermore, while pulsed laser source 1 is often an ultrashort pulse laser source, in some cases, a pulsed laser source with a wider pulse width than an ultrashort pulse laser source is used to generate SC light, and such laser sources are also sometimes used. [Explanation of Symbols]

[0076] 1. Pulsed laser source 10 Light source device 2 Nonlinear elements 31 Notch Filter 32 Dichroic Mirrors 33 Multiplexing elements 351 Transmissive VBG Filter 352 Reflective VBG Filter 353 Transmissive Chirp VBG Filter 354 Reflective Chirp VBG Filter 4. Extension element 41 Fiber 42 Fibers 51 Array waveguide diffraction grating 52 Multiplexing elements 6 Receiver 601 Photoreceiver 602 Receiver 61 AD Converters 7 Calculation means S Object

Claims

1. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, It includes attenuation means that attenuates the light of the oscillation wavelength of the pulsed laser source contained in the supercontinuous light emitted from the nonlinear element without reducing its intensity to zero. The attenuation means is a volume Bragg diffraction grating filter, The device includes an extension element that extends the pulse width of the supercontinuous light emitted from the nonlinear element so that the relationship between the wavelength of light and time within the pulse becomes one-to-one. The broadband pulse light source device is characterized in that the extension element is provided at a position where the supercontinuum light, whose oscillation wavelength has been attenuated by the attenuation means, is incident.

2. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, It includes attenuation means for attenuating the light of the oscillation wavelength of the pulsed laser source contained in the supercontinuous light emitted from the nonlinear element, The broadband pulsed light source device is characterized in that the attenuation means is a dichroic mirror, and the oscillation wavelength of the pulsed laser source is within the divided wavelength range of the dichroic mirror.

3. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, It includes attenuation means for attenuating the light of the oscillation wavelength of the pulsed laser source contained in the supercontinuous light emitted from the nonlinear element, The broadband pulsed light source device is characterized in that the attenuation means is a first and second dichroic mirror, the oscillation wavelength of the pulsed laser source is within the divided wavelength range of these dichroic mirrors, and the second dichroic mirror is a multiplexing element that combines the light divided by the first dichroic mirror.

4. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, An attenuation means for attenuating the light of the oscillation wavelength of a pulsed laser source contained in the supercontinuous light emitted from a nonlinear element without reducing its intensity to zero, The system includes a divider that spatially divides the supercontinuous light emitted from the nonlinear element into light in each wavelength range, The broadband pulsed light source device as described above, characterized in that the attenuation means is a filter that attenuates the light of the oscillation wavelength of the pulsed laser source from among the light of each wavelength range divided by the divider (excluding one that reduces the intensity of the light of the oscillation wavelength of the pulsed laser source to zero).

5. The broadband pulse light source device according to claim 4, characterized in that the divider is an array waveguide diffraction grating.

6. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, It includes attenuation means that attenuates the light of the oscillation wavelength of the pulsed laser source contained in the supercontinuous light emitted from the nonlinear element without reducing its intensity to zero. The broadband pulsed light source device is characterized in that the attenuation means is an array waveguide diffraction grating that spatially divides the supercontinuous light emitted from the nonlinear element into light in each wavelength range while the light at the oscillation wavelength of the pulsed laser source is attenuated (excluding one that reduces the intensity of the light at the oscillation wavelength of the pulsed laser source to zero).

7. The broadband pulsed light source device according to claim 6, characterized in that the oscillation wavelength of the pulsed laser source is within the boundary wavelength range of the output waveguide of the array waveguide diffraction grating.

8. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, An attenuation means for attenuating the light of the oscillation wavelength of the pulsed laser source contained in the supercontinum light emitted from a nonlinear element, It includes a stretching element that stretches the pulse width of supercontinium light emitted from a nonlinear element so that the relationship between the wavelength of light and time within the pulse is one-to-one. The attenuation means is a dichroic mirror, and the oscillation wavelength of the pulsed laser source is within the divided wavelength range of this dichroic mirror. The broadband pulse light source device is characterized in that the stretching element comprises a first stretching element that stretches the pulse width of light reflected by a dichroic mirror and a second stretching element that stretches the pulse width of light transmitted through the dichroic mirror.

9. The broadband pulse light source device according to claim 8, characterized in that the first extension element and the second extension element are fibers with different lengths or dispersion characteristics.

10. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, An attenuation means for attenuating the light of the oscillation wavelength of the pulsed laser source contained in the supercontinum light emitted from a nonlinear element, It includes a stretching element that stretches the pulse width of supercontinium light emitted from a nonlinear element so that the relationship between the wavelength of light and time within the pulse is one-to-one. The broadband pulsed light source device is characterized in that the attenuation means is a dichroic mirror, the oscillation wavelength of the pulsed laser source is within the divided wavelength range of the dichroic mirror, and the dichroic mirror is arranged on the output side of the extension element.

11. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, An attenuation means for attenuating the light of the oscillation wavelength of the pulsed laser source contained in the supercontinum light emitted from a nonlinear element, It includes a stretching element that stretches the pulse width of supercontinium light emitted from a nonlinear element so that the relationship between the wavelength of light and time within the pulse is one-to-one. The attenuation means is a first and second dichroic mirror, and the oscillation wavelength of the pulsed laser source is within the divided wavelength range of these dichroic mirrors. The stretching element comprises a first stretching element that stretches the pulse width of light reflected by the first dichroic mirror, and a second stretching element that stretches the pulse width of light transmitted through the first dichroic mirror. A broadband pulsed light source device characterized in that the second dichroic mirror is a multiplexing element that combines the light emitted from the first and second extension elements.

12. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, An attenuation means for attenuating the light of the oscillation wavelength of the pulsed laser source contained in the supercontinum light emitted from a nonlinear element, It includes a stretching element that stretches the pulse width of supercontinium light emitted from a nonlinear element so that the relationship between the wavelength of light and time within the pulse is one-to-one. The system includes a divider that spatially divides the supercontinuous light emitted from the aforementioned nonlinear element into light in each wavelength range. The attenuation means is a filter that attenuates the light of the oscillation wavelength of the pulsed laser source from among the light of each wavelength range divided by the divider. The extension element consists of multiple fibers arranged in parallel on the output side of the divider. A broadband pulsed light source device characterized in that each fiber is a fiber into which light of each divided wavelength range is incident, and the length or dispersion characteristics of the fiber differ depending on the wavelength range of the incident light.

13. The broadband pulse light source device according to claim 12, characterized in that the divider is an array waveguide diffraction grating.

14. A pulsed laser source, A nonlinear element that emits supercontinuous light by generating a nonlinear effect on light from a pulsed laser source, An attenuation means for attenuating the light of the oscillation wavelength of the pulsed laser source contained in the supercontinum light emitted from a nonlinear element, It includes a stretching element that stretches the pulse width of supercontinium light emitted from a nonlinear element so that the relationship between the wavelength of light and time within the pulse is one-to-one. The attenuation means is an array waveguide diffraction grating that spatially divides the supercontinuous light emitted from the nonlinear element into light in each wavelength range while attenuating the light at the oscillation wavelength of the pulsed laser source. The extension element is a fiber connected to each output-side waveguide of the array waveguide diffraction grating. A broadband pulsed light source device characterized in that each fiber has different length or dispersion characteristics depending on the wavelength range of the incident light.

15. The broadband pulsed light source device according to claim 14, characterized in that the oscillation wavelength of the pulsed laser source is within the boundary wavelength range of the output waveguide of the array waveguide diffraction grating.

16. A broadband pulse light source device according to claim 1 or any of claims 10 to 15, A light receiver receives light from an object irradiated with broadband pulsed light from this broadband pulsed light source device, A computation means for converting the output signal from the photodetector into a spectrum, A spectroscopic measuring device characterized by being equipped with the following features.

17. A broadband pulse light source device according to claim 8 or 9, A light receiver receives light from an object irradiated with broadband pulsed light from this broadband pulsed light source device, A computation means for converting the output signal from the photodetector into a spectrum, It is equipped with, A spectroscopic measuring device characterized by having a first photodetector into which light reflected from a dichroic mirror is incident, and a second photodetector into which light transmitted through the dichroic mirror is incident.

18. A light receiving step of receiving light from an object irradiated with broadband pulsed light from a broadband pulsed light source device according to claim 1 or any of claims 10 to 15 using a light receiver, A conversion step in which the output signal from the photodetector is converted into a spectrum by a calculation means, A spectroscopic measurement method characterized by comprising the following features.

19. A light receiving step of receiving light from an object irradiated with broadband pulsed light from the broadband pulsed light source device according to claim 8 or 9 using a light receiver, A conversion step in which the output signal from the photodetector is converted into a spectrum by a calculation means, It is equipped with, The system is provided with a first light receiver into which light reflected from the dichroic mirror is incident, and a second light receiver into which light transmitted through the dichroic mirror is incident, and the light receiving step is a step in which light is received by the first and second light receivers. A spectroscopic measurement method characterized in that the conversion step is a step of converting the output signals from the first and second photodetectors into spectra using a calculation means.

20. A light receiving step of receiving light from an object irradiated with broadband pulsed light from a broadband pulsed light source device according to claim 1 or any of claims 10 to 15 using a light receiver, The process involves analyzing the object by processing the output signal from the light receiver using a calculation means and comparing it with a standard value. It is equipped with, A spectroscopic analysis method characterized in that the intensity range of supercontinium light emitted from a broadband pulsed light source device is 3 dB or less.

21. A light receiving step of receiving light from an object irradiated with broadband pulsed light from the broadband pulsed light source device according to claim 8 or 9 using a light receiver, The process involves analyzing the object by processing the output signal from the light receiver using a calculation means and comparing it with a standard value. It is equipped with, The system is provided with a first light receiver into which light reflected from the dichroic mirror is incident, and a second light receiver into which light transmitted through the dichroic mirror is incident, and the light receiving step is a step in which light is received by the first and second light receivers. A spectroscopic analysis method characterized in that the intensity range of supercontinium light emitted from a broadband pulsed light source device is 3 dB or less.

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