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

Abstract

The present application provides a kind of wideband pulse light source device with excellent performance, which solves the problem of SC light with seed light wavelength region remaining at high intensity. The light from the pulse laser source (1) is made to generate nonlinear effect by the nonlinear element (2) to generate supercontinuum light, and the light of the oscillation wavelength of the residual pulse laser source (1) is attenuated when being split by the dichroic mirror (32). The split light is pulse stretched by the optical fiber (41), and is multiplexed by the multiplexing element (33) to irradiate the object (S). The light transmitted through the object (S) is received by the light receiver (6), and the output signal thereof is converted into a spectrum by the operation unit (7).

Description

Technical Field

[0001] The invention of this application relates to a light source device that emits broadband pulsed light, and also to a device and method for performing spectroscopic measurement or analysis of objects using broadband pulsed light. Background Technology

[0002] A typical pulsed light source is the pulsed laser (pulsed laser). In recent years, research on widening the wavelength of pulsed lasers has become prevalent, with a typical example being the generation of supercontinuum light (hereinafter referred to as SC light), which utilizes nonlinear optical effects. SC light utilizes the nonlinear effects generated when high-intensity light interacts with matter; by increasing photon density, nonlinear effects can be actively generated. For example, by focusing high-peak-power light, such as that of a pulsed laser, into an optical fiber with a core diameter of several μm, highly efficient SC light can be generated. Because it is an optical fiber, nonlinear effects are continuously generated during long-distance propagation at high photon density, resulting in a wider bandwidth of SC light. The main nonlinear effects in SC light generation are self-phase modulation, cross-phase modulation, Raman scattering, and four-wave mixing.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-205390 Summary of the Invention

[0006] It is believed that SC light, due to its wide wavelength bandwidth, can be applied to a variety of uses. That is, its properties are expected to be effectively utilized not only in optical communication fields such as multi-wavelength multiplexing communication, but also in fields such as material analysis to investigate the wavelength dependence of materials, and image observation fields such as OCT or fluorescence microscopy.

[0007] In particular, it is believed that broadband pulsed light (wideband-stretched pulsed light), obtained by pulse stretching the pulse width of SC light using a stretching element, can be appropriately used in fields such as spectrometry. With broadband pulsed light, the wavelength range is broadened, but the pulse width (time width) remains narrow. However, if the group delay in a transmission element such as an optical fiber is used, the pulse width can also be broadened. In this case, if an element with appropriate wavelength dispersion characteristics is selected, pulse stretching can be performed in a one-to-one correspondence between the time (elapsed time) and wavelength within the pulse.

[0008] The time-wavelength correspondence of broadband pulsed light, obtained through pulse broadening, can be effectively used for spectroscopic measurements. When broadband pulsed light is received by a receiver, the time-varying intensity of the light detected by the receiver corresponds to the intensity of light at each wavelength, i.e., the spectrum. Therefore, the time-varying output signal of the receiver can be converted into a spectrum, enabling spectroscopic measurements even without the use of special dispersive elements such as diffraction gratings. In other words, by irradiating an object with broadband pulsed light, receiving the light from the object with a receiver, and measuring its time-varying characteristics, the spectroscopic properties of the object (e.g., spectroscopic transmittance) can be determined.

[0009] Thus, the application of SC light in various fields can be expected. However, unique challenges also exist. One is the issue of the peak intensity of the pulsed laser used to generate SC light. The following refers to... Figure 15 This point needs clarification. Figure 15 This is a diagram that conceptually represents the issues in SC light generation.

[0010] As mentioned above, SC light utilizes nonlinear optical effects such as self-phase modulation, four-wave mixing, and Raman scattering generated when ultrashort pulses of light are incident on nonlinear optical elements to generate light of new wavelengths, thereby producing broadband light. Currently, most commercially available SC light sources use ultrashort pulses of light ranging from picoseconds to nanoseconds.

[0011] like Figure 15 As shown in (1), the original ultrashort pulse light (sometimes called seed light, or seeder; hereinafter referred to as seed light) is light with a very narrow frequency band centered on the oscillation wavelength λs. However, if it passes through a nonlinear element such as a nonlinear optical fiber, it becomes like... Figure 15 Broadbanding is performed as shown in (2). At this time, although broadbanding is performed, the seed light spectrum mostly remains wavy in the SC light spectrum. Furthermore, for ease of explanation, the wavelength width (half-value width) that becomes half the intensity of the oscillation wavelength (peak wavelength) λs is taken as the oscillation wavelength region. Figure 15 In (1), Rh is used to represent it.

[0012] Thus, the wavy pattern remaining in the spectrum of seed light can potentially become a problem depending on the application of SC light. This is generally not a major issue when utilizing only a specific wavelength from the broadband of SC light, where that wavelength is not included in the wavelength range of seed light. However, it can become problematic, as in cases where the wavelength dependence of a material needs to be investigated, where it is necessary to irradiate light of the most uniform intensity possible across all wavelengths.

[0013] To illustrate with a more concrete example, when SC light pulses are broadened and used for spectroscopic measurements as described above, the intensity deviation in the SC light spectrum significantly affects the dynamic range of the measurement. Specifically, if the seed light ripple is strongly retained, the light is captured by the receiver and spectroscopically measured with a correspondingly wider dynamic range. In this case, due to the limited number of bits in data processing, the intensity resolution in the measurement reduces the amount of dynamic range expansion. This reduction in intensity resolution, as seen in material analysis in the near-infrared region, leads to a significant decrease in analytical precision or even the inability to analyze minute differences in measured values—a fundamental problem.

[0014] The invention of this application was made to solve the above-mentioned problems of broadband pulsed light sources emitting SC light. Its purpose is to provide a high-performance broadband pulsed light source device that solves the problem of SC light remaining at a high intensity in the wavelength region of seed light, and to develop application technologies using such a light source device.

[0015] Methods used to solve problems

[0016] To address the aforementioned issues, the broadband pulsed light source device of this application is characterized by comprising: a pulsed laser source; a nonlinear element that causes light from the pulsed laser source to produce a nonlinear effect and emit supercontinuum light; and an attenuation unit that attenuates the light of the pulsed laser source's oscillation wavelength contained in the supercontinuum light emitted from the nonlinear element.

[0017] In addition, to solve the above problems, a broadband pulsed light source device can be equipped with a broadening element that broadens the pulse width of the supercontinuous light emitted from the nonlinear element in a one-to-one manner with respect to the wavelength of the light within the pulse and time.

[0018] In addition, to solve the above problems, the attenuation unit can be a notch filter.

[0019] In addition, to address the aforementioned issues, the attenuation unit can be a volumetric Bragg diffraction grating filter.

[0020] In addition, to solve the above problems, the attenuation unit can be a dichroic mirror, and the oscillation wavelength of the pulsed laser source can be within the segmented wavelength region of the dichroic mirror.

[0021] In addition, to solve the above problems, a broadband pulsed light source device can have the following configuration: the attenuation unit is a first and a second dichroic mirror, the oscillation wavelength of the pulsed laser source is within the wavelength division region of these dichroic mirrors, and the second dichroic mirror is a multiplexing element that combines the light divided by the first dichroic mirror.

[0022] In addition, to solve the above problems, a broadband pulsed light source device can be configured as follows: a splitter that spatially divides the supercontinuous light emitted from a nonlinear element into light of various wavelength regions, and an attenuation unit that attenuates the oscillation wavelength of the pulsed laser in the light of each wavelength region divided by the splitter.

[0023] In addition, to address the aforementioned issues, the divider can be an arrayed waveguide diffraction grating.

[0024] In addition, to solve the above problems, the attenuation unit can be an arrayed waveguide diffraction grating, which spatially divides the supercontinuum into light of each wavelength region in a state where the oscillation wavelength of the pulsed laser source in the supercontinuum emitted from the nonlinear element is attenuated.

[0025] In addition, to solve the above problems, the oscillation wavelength of the pulsed laser source can be located within the boundary wavelength region of the exit waveguide of the arrayed waveguide diffraction grating.

[0026] In addition, to solve the above problems, a broadband pulsed light source device can have the following configuration: the attenuation unit is a dichroic mirror, the oscillation wavelength of the pulsed laser source is within the wavelength division region of the dichroic mirror, and the broadening element is a first broadening element that broadens the pulse width of the light reflected to the dichroic mirror, and a second broadening element that broadens the pulse width of the light transmitted through the dichroic mirror.

[0027] In addition, to address the aforementioned issues, the first and second stretching elements can be optical fibers with different lengths or dispersion characteristics.

[0028] In addition, to solve the above problems, a broadband pulsed light source device can have the following configuration: the attenuation unit is a dichroic mirror, the oscillation wavelength of the pulsed laser source is within the segmented wavelength region of the dichroic mirror, and the dichroic mirror is disposed on the emission side of the broadening element.

[0029] In addition, to solve the above problems, a broadband pulsed light source device can have the following configuration: a splitter that spatially divides the supercontinuous light emitted from the nonlinear element into light of various wavelength regions; an attenuation unit that attenuates the oscillation wavelength of the pulsed laser in the light of each wavelength region after being split by the splitter; and a broadening element that consists of multiple optical fibers arranged in parallel on the emission side of the splitter, each optical fiber being the incident optical fiber of the light of each wavelength region after being split, and having a length or dispersion characteristic that varies depending on the wavelength region of the incident light.

[0030] In addition, to solve the above problems, a broadband pulsed light source device can have the following configuration: the attenuation unit is an arrayed waveguide diffraction grating that spatially divides the supercontinuous light into wavelength regions in a state where the oscillation wavelength of the pulsed laser source in the supercontinuous light emitted from the nonlinear element is attenuated; the stretching element is an optical fiber connected to each exit side waveguide of the arrayed waveguide diffraction grating; and the length or dispersion characteristics of each optical fiber are different according to the wavelength region of the incident light.

[0031] In addition, in order to solve the above-mentioned problems, the spectrophotometer of the present invention includes: a light receiver for receiving light from an object irradiated with broadband pulse light from the broadband pulse light source device described above; and a processing unit for converting the output signal from the light receiver into a spectrum.

[0032] In addition, to solve the above-mentioned problems, the spectrophotometer of the present invention includes: the aforementioned broadband pulsed light source device; a light receiver for receiving light from an object, the object being irradiated with broadband pulsed light from the broadband pulsed light source device; and a processing unit for converting the output signal from the light receiver into a spectrum, the attenuation unit being a dichroic mirror, the oscillation wavelength of the pulsed laser source being within the wavelength division region of the dichroic mirror, and a first light receiver and a second light receiver being provided as the light receiver, the light reflected by the dichroic mirror being incident on the first light receiver, and the light transmitted through the dichroic mirror being incident on the second light receiver.

[0033] In addition, in order to solve the above-mentioned problems, the spectrophotometric method of the present invention includes: a light receiving step, wherein a light receiver receives light from an object irradiated with broadband pulse light from the broadband pulse light source device; and a conversion step, wherein an arithmetic unit converts the output signal from the light receiver into a spectrum.

[0034] In addition, to solve the above-mentioned problems, the spectrophotometry method of this application includes: a light receiving step, in which a light receiver receives light from an object irradiated with broadband pulsed light from the broadband pulsed light source device; and a conversion step, in which an arithmetic unit converts the output signal from the light receiver into a spectrum, the attenuation unit is a dichroic mirror, the oscillation wavelength of the pulsed laser source is within the wavelength division region of the dichroic mirror, a first light receiver and a second light receiver are provided as light receivers, light reflected by the dichroic mirror is incident on the first light receiver, and light transmitted through the dichroic mirror is incident on the second light receiver, the light receiving step is the step of receiving light by the first and second light receivers, and the conversion step is the step of converting the output signal from the first and second light receivers into a spectrum using the arithmetic unit.

[0035] In addition, in order to solve the above-mentioned problems, the spectroscopic analysis method of the present invention includes: a light receiving step, wherein a light receiver receives light from an object irradiated by broadband pulse light from the broadband pulse light source device; and a step of analyzing the object by processing the output signal from the light receiver using a processing unit and comparing it with a standard value, wherein the intensity width of the supercontinuous light emitted from the broadband pulse light source device is less than 3 dB.

[0036] Invention Effects

[0037] As explained below, the broadband pulsed light source device of the invention according to this application produces a more flat intensity distribution spectrum because the attenuation unit attenuates the light of the oscillation wavelength of the pulsed laser source. Therefore, a broadband pulsed light source device suitable for applications requiring more uniform intensity SC light over a wide bandwidth can be provided.

[0038] Furthermore, when the attenuation unit is a notch filter, the above-mentioned effects can be obtained cheaply through a simple configuration.

[0039] Furthermore, when the attenuation unit is a volumetric Bragg diffraction grating filter, it is easy to achieve selective attenuation with a narrower frequency band, thus enabling the removal of light from only the oscillation wavelength of the pulsed laser source with high precision.

[0040] Furthermore, when the attenuation unit is a dichroic mirror, since the SC light is wavelength-splitting and selectively attenuated at the same time, the splitting can be effectively used to illuminate the SC light.

[0041] Furthermore, in a configuration equipped with a pulse broadening element, the pulse width is broadened when the elapsed time within the pulse corresponds one-to-one with the wavelength of the light, thus allowing for the emission of SC light that is easier to process.

[0042] Furthermore, in a configuration that includes a splitter and uses a filter to attenuate the oscillation wavelength of the pulsed laser in the split light, pulse broadening can be easily optimized by using optical fibers of different lengths or dispersion characteristics to transmit the light in each wavelength region after the splitting and to broaden the pulses.

[0043] Furthermore, if the arrayed waveguide diffraction grating is configured as an attenuation unit and has the function of selective attenuation, the cost is reduced due to the decrease in the number of components, and the structure becomes simpler. In this case, with the oscillation wavelength of the pulsed laser source located in the boundary wavelength region of the exit waveguide of the arrayed waveguide, it is possible to obtain an effect where no new loss is generated in the arrayed waveguide diffraction grating due to attenuation.

[0044] Furthermore, if the aforementioned broadband pulse light source device, which broadens the pulse in a one-to-one manner with the wavelength of the light within the pulse, is used for spectroscopic measurement, then the time-consuming operation required for scanning a diffraction grating is not needed, and high-speed spectroscopic measurement can be performed.

[0045] In particular, since the oscillation wavelength of the pulsed laser source is selectively attenuated to illuminate a broadband light with uniform spectral intensity for spectroscopic measurement, measurement results can be obtained without significantly expanding the dynamic range. Therefore, a spectroscopic measurement device and method with high intensity resolution can be provided.

[0046] Furthermore, in a configuration that uses a dichroic mirror as an attenuation unit, and in a configuration where different photodetectors receive light from each wavelength region after the segmentation and convert their output signals into a spectrum, it is possible to select an appropriate photodetector based on the wavelength region, thereby optimizing spectrophotometry.

[0047] Furthermore, in spectrophotometric analysis that compares the results of spectrophotometric measurements with standard values, if the spectral intensity width is less than 3 dB, the problem of being unable to capture minute differences in the spectrum and thus being unable to make measurements can be largely avoided. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the broadband pulsed light source device according to the first embodiment.

[0049] Figure 2 This is a schematic diagram of the attenuation unit in the first embodiment.

[0050] Figure 3 This is a schematic diagram showing the various types of volumetric Bragg diffraction grating filters that can be used as attenuation units.

[0051] Figure 4 This is a schematic diagram of the broadband pulsed light source device according to the second embodiment.

[0052] Figure 5 This is a schematic diagram of the attenuation unit in the second embodiment.

[0053] Figure 6 This is a schematic diagram of the broadband pulsed light source device according to the third embodiment.

[0054] Figure 7 This is a schematic diagram of the broadband pulsed light source device according to the fourth embodiment.

[0055] Figure 8 This is a schematic diagram representing pulse broadening.

[0056] Figure 9 This is a schematic diagram of the broadband pulsed light source device according to the fifth embodiment.

[0057] Figure 10 This is a schematic diagram of the arrayed waveguide diffraction grating used in the fifth embodiment.

[0058] Figure 11 This is a schematic diagram illustrating an example of an array of waveguide diffraction gratings forming an attenuation unit.

[0059] Figure 12 This is a schematic diagram of the spectrophotometer according to the first embodiment.

[0060] Figure 13 This is a diagram of the main part of an example of a measurement procedure provided by a spectrophotometer.

[0061] Figure 14 This is a schematic diagram of the spectrophotometer according to the second embodiment.

[0062] Figure 15 This is a diagram that conceptually represents the issues in SC light generation. Detailed Implementation

[0063] Next, the method (implementation method) for carrying out the invention of this application will be described.

[0064] First, the implementation method of the invention of the broadband pulsed light source device will be described. Figure 1 This is a schematic diagram of the broadband pulsed light source device according to the first embodiment.

[0065] This broadband pulsed light source device is a device that emits SC light. For example... Figure 1 As shown, the device includes a pulsed laser source 1, a nonlinear element 2 disposed at the incident position of light from the pulsed laser source 1, and an attenuation unit that selectively attenuates the SC light emitted from the nonlinear element 2.

[0066] As the pulsed laser source 1, an ultrashort pulsed 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 a few picoseconds to a few nanoseconds can be used as the pulsed laser source 1.

[0067] As nonlinear element 2, optical fiber is mostly used. For example, photonic crystal fiber and other nonlinear optical fibers can be used as nonlinear element 2. Single-mode optical fibers are more common, but even multimode fibers can be used as nonlinear element 2 as long as they exhibit sufficient nonlinearity.

[0068] In this embodiment, as described later, a broadband pulsed light source device is envisioned for spectroscopic measurement in the 900–1300 nm range. Therefore, the SC light, broadbanded by the nonlinear element 2, becomes broadband light in the 900–1300 nm range. Furthermore, there is no particularly defined definition for what extent a wavelength region covered as a continuous spectrum can be called a "supercontinuum spectrum." For example, it could be defined as SC light if it is continuous for 30 nm or more, SC light if it is continuous for 50 nm or more, or SC light if it is continuous for 100 nm or more. In the following description, as an example, light generated using nonlinear optical effects that is continuous for 50 nm or more will be defined as SC light. Therefore, the broadband pulsed light source device of this embodiment is a device that emits light with a continuous spectrum of at least 50 nm in any range of 900–1300 nm.

[0069] The attenuation unit, a feature of the broadband pulsed light source device implemented as an example, is a unit that attenuates the light in the wavelength region of the seed light, i.e., the oscillation wavelength of the pulsed laser source 1. Several configurations can be considered for the attenuation unit; in this embodiment, a notch filter 31 is used. (Refer to...) Figure 2 The attenuation unit in the first embodiment will be described. Figure 2 This is a schematic diagram of the attenuation unit in the first embodiment. Wherein, Figure 2 (1) is a schematic diagram showing the spectrum of the SC light emitted in the first embodiment. Figure 2 (2) is a diagram that roughly represents the spectral transmission characteristics of a notch filter used as an attenuation unit.

[0070] like Figure 2 As shown, the notch filter 31, as an attenuation unit, selectively attenuates the light of the oscillation wavelength of the pulsed laser source 1. As described above, the oscillation wavelength region Rh of the pulsed laser source 1 is, for example, defined as the wavelength region with half the width of the peak wavelength (oscillation wavelength) λs. A more preferred characteristic of the notch filter 31 is... Figure 2 As shown, the wavelength with the lowest transmittance (hereinafter referred to as the valley wavelength) can be listed as being consistent with the oscillation wavelength λs of the pulsed laser source 1. However, it is not strictly necessary for them to be consistent, as long as the valley wavelength falls within the range of the oscillation wavelength region Rh of the pulsed laser source 1. Moreover, in the characteristics of the notch filter 31, if the wavelength region where the attenuation rate is 50% or more relative to the maximum value (attenuation rate at the valley wavelength) is defined as the attenuation wavelength region, then as long as the oscillation wavelength λs of the pulsed laser source 1 is within the attenuation wavelength region, the effect is sufficient and it can be implemented.

[0071] The degree to which the notch filter 31 attenuates the light, and even the magnitude of the transmittance at the valley wavelength, depends on the intensity of the ripple of the light at the oscillation wavelength of the pulsed laser source 1. For example, if the intensity is about twice that of light at other wavelengths, the transmittance at the valley wavelength is about 50%, exhibiting a selective attenuation characteristic of about 50%.

[0072] exist Figure 2 In (3), the spectrum of SC light after passing through the notch filter 31, which serves as an attenuation unit, is shown schematically. As shown here, the ripple from the seed light disappears from the spectrum of the SC light after passing through the notch filter, resulting in a flatter spectral waveform. Therefore, a broadband pulsed light source device suitable for applications requiring more uniform intensity of SC light over a wide bandwidth can be provided. In this embodiment, since the notch filter 31 is used as an attenuation unit, the configuration is simple, and the above-mentioned effects can be obtained at a low cost.

[0073] Alternatively, when reducing the ripple from the seed light, the intensity need not be reduced across the entire oscillation wavelength region Rh of the pulsed laser source 1. It is sufficient to reduce the intensity only within the oscillation wavelength λs.

[0074] The notch filter 31 described above is, in most cases, a filter element formed of a dielectric multilayer film. In addition to this, a volume Bragg grating filter can also be used as an attenuation unit. A volume Bragg grating (hereinafter referred to as a VBG filter) is a filter that forms a small region with a periodically changing refractive index in an optical element. By making the period of the refractive index change satisfy the Bragg condition, light of that wavelength can be selectively diffracted. Furthermore, VBG filters, as a Japanese term, are sometimes also labeled as volume Bragg grating, volume-type Bragg grating, or volume Bragg grating. Additionally, because holographic techniques are used to obtain the periodic refractive index change structure, or because the change structure is considered equivalent to a hologram, it is sometimes called a volumetric holographic diffraction grating.

[0075] Such VBG filters include both transmission and reflection types, but either type can be used as the attenuation unit in the implementation. Additionally, chirped VBG filters (chirped VBG filters) are also known, which slightly vary the period of the low / high refractive index. Chirped filters can also be used as attenuation units in the implementation. Figure 3 This is a schematic diagram showing the various types of VBG filters that can be used as these attenuation units.

[0076] exist Figure 3In (1), an example of using a transmission-type VBG filter 351 is shown. In the transmission-type 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 appropriately used as an attenuation unit.

[0077] exist Figure 3 In (2), an example of using a reflective VBG filter 352 is shown. In the case of the reflective type, only light of a specific wavelength λc is reflected in a specific direction according to the period of the refractive index change, while light of other wavelengths is transmitted as is.

[0078] exist Figure 3 Examples of using chirped VBG filters 353 and 354 are shown in (3) and (4). Figure 3 (3) is a transmissive type. Figure 3 (4) is a reflective type.

[0079] In chirped VBG filters 353 and 354, the period of refractive index variation is further periodically changed, thus selectively extracting light within a wavelength range corresponding to this range of variation. That is, in Figure 3 In the (3) transmission-type chirped VBG filter 353, only light with a certain wavelength width (λc1~λc2) is refracted and extracted. Figure 3 In the (4) reflective chirped VBG filter 354, only the light λc1~λc2 is reflected.

[0080] exist Figure 3 In (1) to (4), the light other than λc, λc1 to λc2, which is selectively refracted or reflected, travels along the original optical path (main optical path). The light of λc, λc1 to λc2 travels along an optical path that deviates from the main optical path, but in many cases, beam dampers or other terminal processing for light absorption is configured here. However, if there are no special problems, there are also cases where absorption is not actively performed and the light remains as is. In addition, in order to prevent the return light, VBG filters 351 to 354 are mostly configured with the light incident at an angle, and are mostly in an angled position relative to the main optical path.

[0081] Such VBG filters 351-354 are preferred because they enable a narrower attenuation wavelength range compared to dielectric multilayer notch filters. In the case of dielectric multilayer notch filters, the attenuation wavelength range is sometimes slightly wider than the half-width of the ripple (peak from the seed light) in the SC light, potentially causing attenuation of wavelengths that should not be attenuated. VBG filters offer the advantages of easily achieving narrow-band selective attenuation at the level of the ripple's half-width and removing only the ripple with high precision.

[0082] In addition, conventional VBG filters 351 and 352 are sometimes used for applications such as laser wavelength stabilization, particularly for selective attenuation within a narrow frequency band. Therefore, conventional VBG filters 351 and 352 are preferred when the ripple half-width in SC light is particularly narrow. When the ripple half-width is not so narrow but the attenuation wavelength range is narrower than that of a dielectric multilayer notch filter, chirped VBG filters 353 and 354 are preferred.

[0083] As an example, if the half-width at half-maximum (WWHM) of the ripple in the SC light is 40 nm or more, a notch filter made of dielectric multilayer film can be used. However, if the WWHM is narrower, around 2 nm, a chirped VBG filter 353 or 354 is preferred. Moreover, if it is less than 2 nm, a conventional VBG filter 351 or 352 is preferred.

[0084] Additionally, such VBG filters 351, 352, and chirped VBG filters 353, 354 can be purchased, for example, from OptiGrate Corp. (562 South Econ Circle Oviedo, Florida 32765-4311), or can be specially ordered with a specified wavelength or wavelength band. Furthermore, VBG filters are sometimes labeled as Bragg grating notch filters and are sometimes considered a type of notch filter.

[0085] Next, the broadband pulsed light source device of the second embodiment will be described. Figure 4 This is a schematic diagram of the broadband pulsed light source device according to the second embodiment. In the second embodiment, a dichroic mirror 32 is used as an attenuation unit. Figure 5 This is a schematic diagram of the attenuation unit in the second embodiment. Wherein, Figure 5 Similarly, (1) represents a schematic diagram of the spectrum of the emitted SC light. Figure 5 (2) is a diagram that roughly represents the spectral reflection / transmission characteristics of the dichroic mirror used as an attenuation unit. Figure 5 In (2), the solid line represents the spectral reflection characteristic, and the dashed line represents the spectral transmission characteristic.

[0086] A dichroic mirror is an optical element that splits light into wavelengths, allowing light from one wavelength region to pass through and light from the other wavelength region to reflect. In reality, the transition between transmission and reflection occurs throughout a certain wavelength region; this will be referred to as the "segmented wavelength region." In the following examples, the overlap between the wavelength region where transmittance is less than 80% of its peak value and the wavelength region where reflectance is less than 80% of its peak value is defined as the "segmented wavelength region." Figure 5 As shown, in this embodiment, the oscillation wavelength of the pulsed laser source 1 is within the segmented wavelength region. Furthermore, the wavelength where the transmission and reflection characteristics intersect (the wavelength where transmittance and reflectance are equal) is specifically referred to as the segmented wavelength. The segmented wavelength is typically the center of the segmented wavelength region.

[0087] like Figure 4 As shown, in this embodiment, a multiplexing element 33 is provided to overlap 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 segmented wavelength region and transmits light with wavelengths shorter than the segmented wavelength region. Although the reflection / transmission is reversed, the segmented wavelength region here is approximately the same as the segmented wavelength region in the dichroic mirror 32.

[0088] exist Figure 5 In (3), the spectrum of the SC light superimposed by the multiplexing element 33 is shown. The spectral reflection / transmission characteristics of the dichroic mirror 32, which serves as an attenuation unit, are appropriately selected to flatten the spectral intensity of the emitted SC light. In this example, a dichroic mirror is also used as the multiplexing element 33, so attenuation is also considered here. For example, with an overall attenuation rate of approximately 50% as described above, such as... Figure 5 As shown in (2), the dichroic mirror 32, which serves as an attenuation unit, exhibits a beam splitting reflection / transmission characteristic with both transmission and reflection rates of approximately 50% at the split wavelength. That is, the light at the oscillation wavelength of the pulsed laser source 1 is reflected by approximately 50% and transmitted by approximately 50% in the dichroic mirror 32. In this case, the dichroic mirror 33, serving as a multiplexing element, also exhibits approximately 50% reflection and transmission rates at the split wavelength. Thus, when the oscillation wavelength λs of the pulsed laser source 1 is equal to the split wavelength, the light at the oscillation wavelength λs is ultimately attenuated to approximately 50%. Therefore, the spectrum of the emitted SC light is as follows: Figure 5 As shown in (3), the intensity distribution is flat overall. As can be seen from the above description, in this example, the two dichroic mirrors 32 and 33 become attenuation units.

[0089] In a configuration that uses a dichroic mirror 32 as an attenuation unit, selective attenuation is performed while wavelength division of the SC light, thus enabling efficient SC light illumination through division. This configuration is convenient for situations where it is desirable to illuminate an object with light in two wavelength regions, or where different wavelength regions are to be illuminated in different states.

[0090] Furthermore, the oscillation wavelength λs of the pulsed laser source 1 does not necessarily have to match the segmentation wavelength; as long as it is within the segmentation wavelength region, sufficient effect can be obtained. Additionally, if the segmentation wavelength region is defined as 70% or less instead of 80% or less, the possibility of further attenuation is higher; therefore, 60% or less is preferred, and more preferably preferred.

[0091] Next, the third and fourth embodiments will be described. Figure 6 This is a schematic diagram of the broadband pulsed light source device according to the third embodiment. Figure 7 This is a schematic diagram of the broadband pulsed light source device according to the fourth embodiment.

[0092] like Figure 6 as well as Figure 7 As shown, these broadband pulsed light source devices have a widening element 4 that widens the pulse width of the supercontinuous light emitted from the nonlinear element 2. Figure 6 The third embodiment shown is an embodiment in which a widening element 4 is added to the first embodiment. Figure 7 The fourth embodiment shown is an embodiment in which a widening element 4 is added to the second embodiment. Hereinafter, the widening element 4 will be described. Figure 8 This is a schematic diagram representing pulse broadening.

[0093] The generated SC light has a wide wavelength bandwidth, but the pulse width is still an ultrashort pulse in the femtosecond to picosecond range. In its original state, it is difficult to use depending on the application, therefore pulse broadening is performed. The broadening element 4 can be constructed using an optical fiber with specific group delay characteristics, such as a dispersion-compensating fiber (DCF). For example, if SC light L1, which has a continuous spectrum within a certain wavelength range, is passed through a group delay fiber 41 that has positive dispersion characteristics within that wavelength range, the pulse width is effectively broadened. That is, as... Figure 8 As shown, in SC light L1, although it is an ultrashort pulse, there is light with the longest wavelength λ1 at the beginning of a pulse, and shorter wavelengths gradually appear as time goes by, with the shortest wavelength λ at the end of the pulse. nIf this light is passed through a normally dispersed group-delay fiber 41, then in the normally dispersed group-delay fiber 41, shorter wavelengths of light are delayed in propagation, thus increasing the time difference within a pulse. As a result, when exiting the fiber 41, shorter wavelengths of light are further delayed compared to longer wavelengths. Consequently, the exited SC light L2 becomes light with a broadened pulse width while ensuring the uniqueness of time relative to wavelength. That is, as... Figure 8 As shown on the lower side, at times t1 to t n Relative to wavelengths λ1~λ n The pulses broaden the pulses in a one-to-one correspondence.

[0094] Alternatively, anomalous dispersion fiber can be used as the fiber 41 for pulse broadening. In this case, the SC light is dispersed in a state where the longer wavelength side exists at the beginning of the pulse is delayed, and the shorter wavelength side exists at a later time, thus reversing the time relationship within a pulse. Pulse broadening is performed in a state where the shorter wavelength side exists at the beginning of the pulse, and the longer wavelength side exists as time passes. However, compared to the case of normal dispersion, there are more cases where the propagation distance for pulse broadening needs to be further extended, and the loss is more likely to increase. Therefore, normal dispersion is preferred in this respect.

[0095] Thus, the broadband pulsed light source apparatus according to the third and fourth embodiments can be used for various purposes because it emits broadband pulsed light with both a wider wavelength bandwidth and a wider pulse width. In particular, in these embodiments, the elapsed time within the pulse corresponds one-to-one with the wavelength of the light, thus enabling the emission of broadband pulsed light that is easier to process.

[0096] Next, the broadband pulsed light source device of the fifth embodiment will be described. Figure 9 This is a schematic diagram of the broadband pulsed light source device according to the fifth embodiment.

[0097] The broadband pulsed light source device of the fifth embodiment also includes a broadening element 4. In this embodiment, a splitter is provided to spatially divide the SC light emitted from the nonlinear element 2 into light of various wavelength regions. As the splitter, an array waveguide grating (AWG) 51 is used in this embodiment.

[0098] Figure 10 This is a schematic diagram of the arrayed waveguide diffraction grating used in the fifth embodiment. (See diagram below.) Figure 10As shown, the arrayed waveguide diffraction grating 51 is constructed by forming functional waveguides 512 to 516 on a substrate 511. Each functional waveguide consists of multiple grating waveguides 512 with slightly different optical path lengths, planar waveguides 513 and 514 connected to both ends (incident side and emission side) of the grating waveguides 512, an incident side waveguide 515 that allows light to be incident onto the incident side planar waveguide 513, and emission side waveguides 516 that extract light of various wavelengths from the emission side planar waveguide 514.

[0099] Planar waveguides 513 and 514 are free space. Light incident through the incident-side waveguide 515 is expanded in the incident-side planar waveguide 513 and incident on each grating waveguide 512. The lengths of each grating waveguide 512 are slightly different, thus the phase of the light reaching the end of each grating waveguide 512 is shifted by this difference. Light diffracts from each grating waveguide 512 and exits, but the diffracted light interferes with each other as it passes through the exit-side planar waveguide 514 and reaches the incident end of the exit-side waveguide 516. At this time, due to interference and phase shift, at the incident end of the exit-side waveguide 516, it exhibits particularly strong light at a position corresponding to the wavelength. That is, light of successively different wavelengths is incident on each exit-side waveguide 516, and the light is spatially split. Then, each exit-side waveguide 516 is formed such that each incident end is located at this beam-splitting position.

[0100] Such an array of waveguide diffraction gratings 51 can be fabricated, for example, by surface treatment of a silicon substrate 511. Specifically, a cladding layer (SiO2 layer) is formed on the surface of the silicon substrate 511 using flame deposition, and a core SiO2-GeO2 layer is formed using the same flame deposition method. Then, the SiO2-GeO2 layer is patterned using photolithography to form waveguides 512 to 516. The linewidth of each grating waveguide 512 can be, for example, about 5 to 6 μm.

[0101] The number of emitted waveguides 516 formed also depends on the wavelength width of the broadband pulsed light. However, in the case of light with a continuous spectrum in a wavelength width of about 900 to 1700 nm, for example, the number of emitted waveguides 516 is about 10 to 100, and the light is divided into wavelengths of 3 to 60 nm and emitted.

[0102] In this embodiment, optical fiber 42 is also used as the stretching element 4. In this embodiment, multiple optical fibers 42 are provided as the stretching element 4, which are respectively connected to each of the emission side waveguides 516 of the array waveguide diffraction grating 51.

[0103] Each optical fiber 42 can be identical (of the same material and structure) and of the same length, but it is preferable to use different optical fibers, or even if they are the same fiber, to use different lengths. In this embodiment, the optical fibers 42 transmit light in each wavelength region segmented by the splitter, and pulse broadening is performed during this process. Therefore, pulse broadening can be optimized by using optical fibers with characteristics and lengths corresponding to the wavelength regions. As described above, pulse broadening utilizes group velocity dispersion in the optical fiber; therefore, the characteristic here is dispersion characteristic.

[0104] For example, even with the same optical fiber, it is preferable to use it with varying lengths according to the wavelength region. The amount of group delay in an optical fiber depends on its length; therefore, by using an appropriate fiber length for each wavelength region, optimal pulse broadening can be achieved by ensuring proper group delay in each wavelength region. For example, even when using an optical fiber with normal dispersion characteristics within a certain wavelength range, the absolute value of the dispersion value (negative value) varies with wavelength, thus affecting the slope of time versus wavelength of the light exiting the fiber (pulse-broadened light). Figure 8 The Δλ / Δt ratio is not uniform. In this case, by appropriately selecting the length of each fiber 42 in the above configuration, the Δλ / Δt ratio can be made more uniform. In addition to changing the length of the fiber 42, fibers with different dispersion characteristics can also be used. That is, it is preferable to connect and use fibers 42 with appropriate dispersion characteristics that match the wavelength of the light emitted from each emitting side waveguide 516.

[0105] In addition, such as Figure 9 as well as Figure 10 As shown, in this embodiment, a multiplexing element 52 is provided on the emission side of the multiple optical fibers 42 that serve as the stretching element 4. The multiplexing element 52 is an element that overlaps the light emitted from each optical fiber 42 into a single beam that is emitted 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 fusion type, spatial type, etc., are known, but any type can be used.

[0106] In this fifth embodiment, the attenuation unit is a unit that selectively attenuates the oscillation wavelength of the pulsed laser source 1 in the emitted light of the arrayed waveguide diffraction grating 51, which serves as a divider. Specifically, as... Figure 10As shown, an attenuation filter 34 is provided between the emission-side waveguide 516 of the arrayed waveguide diffraction grating 51, which emits light of the oscillation wavelength of the pulsed laser source 1, and the corresponding optical fiber 42. The attenuation filter 34 can be an ND filter, or a notch filter or VBG filter that selectively attenuates the light of the oscillation wavelength of the pulsed laser source 1. Thus, similar to the embodiments described above, SC light with a flat spectral distribution in intensity is emitted. The attenuation filter 34 can also be provided between the optical fiber 42 transmitting the light of the oscillation wavelength of the pulsed laser source 1 and the multiplexing element 52.

[0107] Besides using the light-reducing filter 34, it can also have selective attenuation capabilities as part of the arrayed waveguide diffraction grating itself. For more information, see [reference needed]. Figure 11 Please provide an explanation. Figure 11 This is a schematic diagram illustrating an example of an array of waveguide diffraction gratings forming an attenuation unit.

[0108] Several examples can be considered where the arrayed waveguide diffraction grating itself constitutes the attenuation unit, but a preferred example is one where the arrayed waveguide diffraction grating is designed and fabricated in such a way that the oscillation wavelength of the pulsed laser source 1 is within a boundary wavelength region of the exit-side planar waveguide of the arrayed waveguide diffraction grating. Figure 11 This example is illustrated below. The boundary wavelength region refers to the area where the coupling strength is below, for example, 80% of the peak value.

[0109] In the arrayed waveguide diffraction grating 51, as described above, a phase difference is imparted in the grating waveguide 512. Taking advantage of the fact that the diffracted light in the exit-side planar waveguide 514 exhibits stronger intensity at different positions according to wavelength due to the phase difference and interference, the incident ends of the exit-side waveguide 516 are positioned at these increasingly stronger positions. Hereinafter, the intensity of the light in the exit-side waveguide 516 will be referred to as the coupling strength. The location and wavelength of the diffracted light where the coupling strength increases is determined by the design of the optical path length difference between each grating waveguide 512, the design of the exit-side planar waveguide 514, etc. That is, as... Figure 11 As shown, λ1, λ2, λ3,···λ n The coupling intensity of the light increases at their respective positions. At this time, the oscillation wavelength of pulsed laser source 1 is located at λ1, λ2, λ3, ..., λ... n Within any boundary wavelength region of each wavelength. In this way, with the light of the oscillating wavelength effectively attenuated, the SC light is spatially divided by wavelength.

[0110] In the above configuration, λ1, λ2, λ3, ..., λ n δλ in the diagram corresponds to the wavelength resolution in the arrayed waveguide diffraction grating 51, but the boundary wavelength region is slightly narrower than the width of δλ. If an example of a preferred design is shown, then... Figure 11 As shown, the wavelength at the center of a boundary wavelength region is made to match the oscillation wavelength λs of pulsed laser source 1.

[0111] Thus, if selective attenuation can be achieved as a function of the arrayed waveguide diffraction grating 51 itself, a light-attenuating filter is unnecessary, thus simplifying the structure and reducing costs. In the above example, the oscillation wavelength λs of the pulsed laser source 1 is at the center of the boundary wavelength region, but the effect is achieved as long as it is within the boundary wavelength region. Furthermore, if the boundary wavelength region is defined as 60% or less instead of 80% or less, further attenuation can be achieved, so it is preferable, and more preferably, 40% or less. In addition to the above configuration, the oscillation wavelength of the pulsed laser source 1 can also be placed within one of the wavelength regions divided by the arrayed waveguide diffraction grating 51, and a portion for light attenuation can be provided in the waveguide (e.g., the corresponding grating waveguide 512) of that wavelength region. However, in this configuration, the entire wavelength region divided by the arrayed waveguide diffraction grating 51 is attenuated, thus generating new losses accordingly. In the configuration where the oscillation wavelength of the pulsed laser source 1 is placed within a boundary wavelength region, there are no new losses, so this is preferable.

[0112] In the fifth embodiment, as a component constituting the pulse broadening element 4, an optical fiber 42 is connected to each emitting waveguide 516 to perform pulse broadening in a one-to-one time-to-wavelength correspondence. Furthermore, the characteristics and / or length of each optical fiber 42 are appropriate according to the wavelength region of transmission, thus optimizing the pulse broadening.

[0113] Next, the implementation methods of the spectrophotometer and the spectrophotometer will be described. Figure 12 This is a schematic diagram of the spectrophotometer according to the first embodiment. Figure 12 The spectrophotometer shown includes: a broadband pulsed light source device 10; an illumination optical system 100 that irradiates an object S with broadband pulsed light emitted from the broadband pulsed light source device 10; a light receiver 6 disposed at the position where the light from the object S is incident; and a calculation unit 7 that calculates the spectrophotometric spectrum of the object S according to the output from the light receiver 6.

[0114] The broadband pulsed light source device (hereinafter referred to as the light source device) 10 adopts the structure of the fourth embodiment with the broadening element 4, but it can also be the structure of the third or fifth embodiment. In this embodiment, the illumination optical system 100 includes a beam expander 101. Although the light from the light source device 10 is time-broadened broadband pulsed light, it is light from the pulsed laser source 1, and the beam diameter is relatively small. In addition, there are cases where a scanning mechanism such as a galvanometer mirror is provided to cover a wider illumination area by scanning the beam.

[0115] As the light receiver 6, a light receiver that converts the intensity of received light into an electrical signal and outputs that signal is employed. Specifically, a photodetector such as a photodiode with sensitivity within the measured wavelength range is used. In this embodiment, it is envisioned that the absorption spectrum of the object S is being measured; therefore, the light receiver 6 is positioned at the point where transmitted light from the object S is incident. A transparent support plate 8 is provided for mounting the object S. The illumination optical system 100 illuminates the object from above, and the light receiver 6 is positioned below the support plate 8.

[0116] In this embodiment, a general-purpose PC is used as the arithmetic unit 7. An AD converter 61 is provided between the light receiver 6 and the arithmetic unit 7, and the output of the light receiver 6 is input to the arithmetic unit 7 via the AD converter 61.

[0117] The arithmetic unit 7 includes a processor 71 and a storage unit (such as a hard disk drive) 72. The storage unit 72 contains a measurement program 73 that converts the output signal from the photodetector 6 into a spectrum, as well as other necessary programs.

[0118] In this embodiment, since a light source device 10 is used to irradiate a broadband broadened pulse light that ensures the uniqueness of the time and wavelength, the measurement procedure 73 is also optimized accordingly. Figure 13 This is a diagram that roughly illustrates the main part of an example of a measurement procedure 73 provided by a spectrophotometer.

[0119] Figure 13 An example is the measurement procedure 73 measuring the absorption spectrum (spectral absorptivity). Reference spectral data is used in the calculation of the absorption spectrum. Reference spectral data are the values ​​of each wavelength used as a reference for calculating the absorption spectrum. Reference spectral data is obtained by directing light from the light source device 10 onto the photodetector 6 without passing through the object S. That is, the 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 arithmetic unit 7 via the AD converter 61 to obtain the value of each time resolution Δt. Each value is stored as a reference intensity (V1, V2, V3, ...) for each time Δt at each moment t1, t2, t3, ... . The time resolution Δt is a quantity determined by the response speed (signal output period) of the photodetector 6, referring to the time interval of the output signal.

[0120] The reference intensities V1, V2, V3, ... at each time point t1, t2, t3, ... are the intensities (spectral values) of the corresponding wavelengths λ1, λ2, λ3, ... . The relationship between the times t1, t2, t3, ... within a pulse and the wavelength is investigated beforehand, and the values ​​V1, V2, V3, ... at each time point are the values ​​of λ1, λ2, λ3, ...

[0121] Then, when light passing through the object S is incident on the photodetector 6, the output from the photodetector 6 is also stored in the memory (v1, v2, v3, ...) as values ​​(measured values) at each time t1, t2, t3, ... via the AD converter 61. Each measured value is compared with reference spectral data (v1 / V1, v2 / V2, v3 / V3, ...), and the result is the absorption spectrum (strictly speaking, the values ​​obtained by taking the logarithm of the reciprocal). In order to perform the above-described calculation process, the measurement program 73 is programmed.

[0122] Next, the operation of the above-described spectrophotometer will be explained. The following explanation also describes an embodiment of the spectrophotometer method. When performing a spectrophotometer measurement using the spectrophotometer of this embodiment, the light source device 10 is activated without the object S being placed, allowing light that does not pass through the object S to directly enter the photodetector 6. The output signal from the photodetector 6 is processed, and reference spectral data is obtained in advance. Based on this, the object S is placed on the support plate 6, and the light source device 10 is activated again. Then, light transmitted through the object S is allowed to enter the photodetector 6, and the output signal from the photodetector 6 is input to the processing unit 7 via the AD converter 61. The spectrum is obtained using the measurement program 73.

[0123] In the example above, the absorption spectrum of transmitted light from the object S was measured. However, there are also cases where the spectroscopic characteristics, such as the reflection spectrum (spectral reflectance) of reflected light from the object S, or the internal scattered light from the object S, are measured. That is, the light from the object S can be transmitted light, reflected light, scattered light, etc., from the object S that has been illuminated.

[0124] In addition, when measuring the light source device 10 and the sensitivity characteristics of the light receiver 6 change over time, a reference spectrum is obtained (measurement in the state where the object S is not configured), and a calibration operation to update the reference spectrum is performed periodically.

[0125] According to the spectrophotometer and spectrophotometer method of this embodiment, since the pulse width of the broadband pulse light from the pulse light source 1 is broadened in a one-to-one manner with the relationship between the elapsed time and the wavelength within a pulse and then irradiated onto the object S for spectrophotometer measurement, a time-consuming operation such as scanning of a diffraction grating is not required, and high-speed spectrophotometer measurement can be performed.

[0126] In particular, since the oscillation wavelength of the pulsed laser source 1 is selectively attenuated to illuminate a broadband light with uniform spectral intensity for spectroscopic measurement, measurement results can be obtained without significantly expanding the dynamic range. Therefore, a spectroscopic measurement device with high intensity resolution can be provided.

[0127] The above points are particularly significant when used for materials analysis based on minute differences in spectra. This will be illustrated with a more specific analytical example.

[0128] As a more concrete example of the aforementioned spectrophotometric methods, near-infrared spectrophotometry can be cited. Near-infrared spectrophotometry is a technique for quantifying materials based on minute differences in absorption spectra. Because of the numerous variables and interactions among various factors in the absorption of light in the near-infrared region, chemometrics (multivariate analysis) methods are often employed. In such spectrophotometry, absorption spectra of multiple samples with known amounts of the target component are obtained through spectrophotometry, and regression coefficients are calculated by performing regression analysis (PLS regression, etc.) on the multiple measurement results. Then, the same spectrophotometric measurement is performed on an unknown sample (the target substance), and the regression coefficients are applied to the obtained absorption spectra to quantify the target component.

[0129] In such spectroscopic analysis, if the dynamic range is wide, the intensity resolution decreases due to the limitation of bit depth in data processing. If the intensity resolution decreases, it becomes impossible to capture minute differences in the absorption spectrum, making analysis impossible. However, if a broadband pulsed light source device as described above is used, the dynamic range becomes smaller, thus enabling the capture of minute differences in the absorption spectrum for quantitative analysis. In spectroscopic analysis that compares values ​​obtained through such spectroscopic measurements with reference values, if the spectral intensity width of the SC light is set to, for example, 3 dB or less, the aforementioned problem does not occur. Furthermore, 3 dB or less sometimes refers to the entire wavelength range of the light output from the broadband pulsed light source device, but even if this is not the case, as long as it is 3 dB or less in the wavelength range used in the analysis, it is sufficient to use such a light source device. For example, there are cases where the spectral intensity width is less than 3dB in the wavelength region of 900–1300 nm, and there are also cases where the spectral intensity width is less than 3dB in any wavelength region of 900–1300 nm with a width of more than 30 nm, more than 50 nm, or more than 100 nm.

[0130] Next, the spectrophotometer and spectrophotometer method of the second embodiment will be described. Figure 14 This is a schematic diagram of the spectrophotometer according to the second embodiment.

[0131] The spectrophotometer in the second embodiment is the same as that in the first embodiment, with a light source device 10 equipped with a dichroic mirror 32 serving as an attenuation unit. The difference between the spectrophotometer in the second embodiment and that in the first embodiment is that no multiplexing element is provided. Light from each wavelength region separated by the dichroic mirror 32 is irradiated onto the object S, and different light receivers 601 and 602 receive the light from the object S irradiated with light from each wavelength region.

[0132] In this example, support plates 8 are provided on the two optical paths on the emission side of the dichroic mirror 32, and light receivers 601 and 602 are respectively arranged at the positions where light transmitted through the object S on the support plates 8 is received. For example, if the dichroic mirror 32 has the characteristic of transmitting wavelengths longer than the split wavelength and reflecting shorter wavelengths, the light on the longer wavelength side is received by the first light receiver 601, and the light on the shorter wavelength side is received by the second light receiver 602. In addition, as in the fourth embodiment, optical fibers 41 are arranged as stretching elements 4 in each optical path.

[0133] In this method, the oscillation wavelength of the pulsed laser source 11 is also within the wavelength division region of the dichroic mirror 32. The arithmetic unit 7 converts the output signal from the first photodetector 601 to obtain the spectrum in the wavelength region longer than the divided wavelength, and converts the output signal from the second photodetector 602 to obtain the spectrum in the wavelength region shorter than the divided wavelength. Then, for the divided wavelength, the output signals from either photodetector 601 or 602 are converted to obtain the spectrum. For example, similarly, when the seed light has twice the spectral intensity, if the reflectivity and transmittance are set to 50%, the light is incident on either photodetector 601 or 602 at a reduced intensity of 50%. Therefore, as a whole, the measurement system can be measured without being affected by the ripple of the seed light.

[0134] By receiving the light split by the dichroic mirror 32 through different photodetectors 601 and 602, appropriate photodetectors can be used according to the wavelength region, thus optimizing the spectrophotometry.

[0135] The above points are closely related to the light source device 10 that emits SC light. While the light source device 10, as an SC light source, can emit pulsed light with a wider bandwidth, it is difficult to cover a wide bandwidth with a single photodetector. For example, in the case of performing spectroscopic measurements in the near-infrared region, an InGaAs diode photodetector using InGaAs as the photodetector unit is preferred. However, when performing spectroscopic measurements covering a wider bandwidth from the visible to the near-infrared region, the InGaAs diode photodetector does not have sufficient sensitivity in the short wavelength region below 900 nm. For example, a Si diode photodetector using a Si photodiode as the photodetector unit can be used as a photodetector that has sufficient sensitivity in the wavelength region below 900 nm. Therefore, using an InGaAs photodetector and a Si diode photodetector as the first and second photodetectors 601 and 602 is extremely suitable for a configuration that covers a wider wavelength range from the visible to the near-infrared region for spectroscopic measurements. If other examples of light receivers are shown, for example, a CdS light receiver can be used in the visible region, and a PbS light receiver, an InSb light receiver, etc. can be used in the near-infrared region.

[0136] exist Figure 14 In the illustrated embodiment, since the support plates 8 are provided on each optical path, as a configuration for spectrophotometry, an object S is sequentially placed on the support plates 8, and spectrophotometry is performed in each wavelength region. These measurements are then integrated to obtain the spectrophotometry result for the entire wavelength. Depending on the situation, a configuration can also be adopted in which the support plates 8 are a single unit, switched using a gate or the like. The branched optical paths are overlapped again using a dichroic mirror or the like, and the support plates are placed there. Switching is performed using a gate, allowing light from each wavelength region to sequentially illuminate the object on the support plate. Furthermore, while switching is performed by the gate, the light receiver is also switched, and spectrophotometry in each wavelength region is performed sequentially.

[0137] Furthermore, although detailed explanations are omitted, the configuration of using different photodetectors for each wavelength region can also be employed in configurations using splitters that perform fine wavelength division, such as arrayed waveguide diffraction gratings. For example, when using the arrayed waveguide diffraction grating 51 described above, each optical fiber 42 connected to the emission side waveguide 516 is divided into two groups according to wavelength, and each group is multiplexed by a multiplexing element and irradiated onto the object S. Then, one photodetector receives the light from the object S irradiated by the group irradiated from the longer wavelength side, and the other photodetector receives the light from the object S irradiated by the group irradiated from the shorter wavelength side.

[0138] Furthermore, whether using the dichroic mirror 32 or a divider such as the arrayed waveguide diffraction grating 51, there may be cases where the light-receiving frequency bands are more than three. That is, there may also be cases where more than three light receivers are used to perform photoelectric conversion corresponding to the frequency bands.

[0139] Furthermore, in various embodiments using dimmers such as the dichroic mirror 32 and the arrayed waveguide diffraction grating 51, when the stretching element 4 is provided, the stretching element 4 can also be positioned on the incident side of the dichroic mirror 32 and the stretching element. That is, the configuration can be that the segmentation based on the dichroic mirror 32 and the stretching element is performed after pulse stretching. However, in the case where pulse stretching is performed separately after segmentation by the dichroic mirror 32 and the stretching element, as described above, a pulse stretching configuration corresponding to the wavelength region can be adopted. In addition, since the sharp ripples of the oscillation wavelength of the pulsed laser source 1 will not be incident on the stretching element 4, it is also preferable in terms of protecting the stretching element 4.

[0140] Furthermore, the selective attenuation of the oscillation wavelength of the pulsed laser source 1 is a dynamic range issue in the measurement. Therefore, attenuation only needs to be performed at a certain position in the optical path between the nonlinear element 2 and the photodetector 6. Depending on the situation, an attenuation unit may also be provided between the object S and the photodetector 6. However, similarly, from the perspective of protecting the object S from the sharp ripples from the seed light, it is preferable to provide an attenuation unit in the optical path in front of the object S.

[0141] Furthermore, the term "attenuation" based on the attenuation unit is used in a broad sense and is not limited to the situation where light is absorbed and its intensity weakens in a certain element. Since the main purpose is to keep the dynamic range in the photodetector from widening, it also includes the following situation: by reflecting or scattering a portion of the light of the pulsed laser source's oscillation wavelength and removing it from the optical path, the intensity incident on the photodetector is reduced.

[0142] Furthermore, in the aforementioned spectrophotometric apparatus and method, the following configuration is sometimes adopted: light from the light source device 10 is split into measurement and reference light using a beam splitter or the like; light that has passed through the object S is detected by a light receiver 6; and a reference light receiver is provided so that the light does not pass through the object S but is incident on the object as is. In this configuration, since reference spectral data is obtained in real time, no additional calibration work is required, resulting in improved measurement efficiency.

[0143] In addition to the aforementioned spectrophotometry and spectroscopic analysis, the broadband pulsed light source device can be used for various other applications. For example, it can be utilized in applications such as OCT (Optical Coherence Tomography) and fluorescence microscopy, where objects are visualized and observed.

[0144] In addition, pulsed laser source 1 is mostly an ultrashort pulsed laser source, but there are also cases where pulsed laser sources with a pulse width wider than ultrashort pulsed laser sources are used to generate SC light, and such laser sources are sometimes used.

[0145] Explanation of reference numerals in the attached figures

[0146] 1. Pulsed laser source

[0147] 10. Light source device

[0148] 2. Nonlinear elements

[0149] 31 Notch Filter

[0150] 32 dichroic mirror

[0151] 33 Multiplexing Components

[0152] 351 Transmissive VBG Filter

[0153] 352 Reflective VBG Filter

[0154] 353 Transmissive Chirped VBG Filter

[0155] 354 Reflective Chirped VBG Filter

[0156] 4. Extended Components

[0157] 41 optical fibers

[0158] 42 optical fibers

[0159] 51 Arrayed waveguide diffraction grating

[0160] 52 Multiplexing Components

[0161] 6. Light receiver

[0162] 601 Photodetector

[0163] 602 Photodetector

[0164] 61 AD converter

[0165] 7. Operational Unit

[0166] S object

Claims

1. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. as well as The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum emitted from the nonlinear element in a manner that prevents its intensity from becoming zero. The attenuation unit is a volumetric Bragg diffraction grating filter.

2. The broadband pulsed light source device as described in claim 1, characterized in that, The broadband pulsed light source device includes a broadening element that broadens the pulse width of the supercontinuous light emitted from the nonlinear element in a one-to-one manner with respect to the wavelength of the light within the pulse and time.

3. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum light emitted from the nonlinear element. as well as A broadening element is used to broaden the pulse width of the supercontinuum light emitted from the nonlinear element in a one-to-one manner with respect to the wavelength of the light within the pulse and time. The broadening element is positioned at the location where the supercontinuum light, whose oscillation wavelength has been attenuated by the attenuation unit, is incident.

4. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum light emitted from the nonlinear element. The attenuation unit is a dichroic mirror, and the oscillation wavelength of the pulsed laser source is within the segmented wavelength region of the dichroic mirror. The segmented wavelength region of the dichroic mirror is the overlapping part of the wavelength region where the transmittance is less than 80% of the maximum value and the wavelength region where the reflectance is less than 80% of the maximum value.

5. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum light emitted from the nonlinear element. The attenuation unit is a first dichroic mirror and a second dichroic mirror. The oscillation wavelength of the pulsed laser source is within the segmented wavelength region of these dichroic mirrors. The second dichroic mirror is a multiplexing element that combines the light split by the first dichroic mirror. The segmented wavelength region of the first dichroic mirror and the second dichroic mirror is the overlapping part of the wavelength region where the transmittance is less than 80% of the maximum value and the wavelength region where the reflectance is less than 80% of the maximum value.

6. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the light of the pulsed laser source containing the supercontinuum light emitted from the nonlinear element in a manner that does not reduce its intensity to zero. as well as The divider spatially splits the supercontinuum light emitted from the nonlinear element into light in different wavelength regions. The attenuation unit is a filter that attenuates the light of the oscillation wavelength of the pulsed laser source in the light of each wavelength region after being divided by the splitter, wherein the case where the intensity of the light of the oscillation wavelength of the pulsed laser source is zero is excluded.

7. The broadband pulsed light source device as described in claim 6, characterized in that, The divider is an arrayed waveguide diffraction grating.

8. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. as well as The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum emitted from the nonlinear element in a manner that prevents its intensity from becoming zero. The attenuation unit is an arrayed waveguide diffraction grating. Under the condition that the light of the oscillation wavelength of the pulsed laser source in the supercontinuous light emitted from the nonlinear element is attenuated, the arrayed waveguide diffraction grating spatially divides the supercontinuous light into light of each wavelength region, excluding the case where the intensity of the light of the oscillation wavelength of the pulsed laser source is zero.

9. The broadband pulsed light source device as described in claim 8, characterized in that, The oscillation wavelength of the pulsed laser source is located within the boundary wavelength region of the exit waveguide of the arrayed waveguide diffraction grating.

10. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum light emitted from the nonlinear element. as well as A broadening element that broadens the pulse width of the supercontinuum light emitted from the nonlinear element in a one-to-one manner with respect to the wavelength of the light within the pulse and time. The attenuation unit is a dichroic mirror, and the oscillation wavelength of the pulsed laser source is within the segmented wavelength region of the dichroic mirror. The segmented wavelength region of the dichroic mirror is the overlap between wavelength regions where the transmittance is less than 80% of the maximum value and wavelength regions where the reflectance is less than 80% of the maximum value. The broadening element is a first broadening element that broadens the pulse width of the light reflected to the dichroic mirror and a second broadening element that broadens the pulse width of the light transmitted through the dichroic mirror.

11. The broadband pulsed light source device as described in claim 10, characterized in that, The first stretching element and the second stretching element are optical fibers with different lengths or dispersion characteristics.

12. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum light emitted from the nonlinear element. as well as A broadening element that broadens the pulse width of the supercontinuum light emitted from the nonlinear element in a one-to-one manner with respect to the wavelength of the light within the pulse and time. The attenuation unit is a dichroic mirror, and the oscillation wavelength of the pulsed laser source is within the segmented wavelength region of the dichroic mirror. The dichroic mirror is disposed on the emission side of the broadening element. The segmented wavelength region of the dichroic mirror is the overlapping part of the wavelength region where the transmittance is less than 80% of the maximum value and the wavelength region where the reflectance is less than 80% of the maximum value.

13. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum light emitted from the nonlinear element. as well as A broadening element that broadens the pulse width of the supercontinuum light emitted from the nonlinear element in a one-to-one manner with respect to the wavelength of the light within the pulse and time. The attenuation unit comprises a first dichroic mirror and a second dichroic mirror. The oscillation wavelength of the pulsed laser source lies within the segmented wavelength region of these dichroic mirrors. The segmented wavelength region of the first and second dichroic mirrors is the overlapping portion of wavelength regions where the transmittance is less than 80% of the maximum value and wavelength regions where the reflectance is less than 80% of the maximum value. The broadening element is a first broadening element that broadens the pulse width of the light reflected to the first dichroic mirror, and a second broadening element that broadens the pulse width of the light transmitted through the first dichroic mirror. The second dichroic mirror is a multiplexing element that combines the light emitted from the first broadening element and the second broadening element.

14. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum light emitted from the nonlinear element. as well as A broadening element that broadens the pulse width of the supercontinuum light emitted from the nonlinear element in a one-to-one manner with respect to the wavelength of the light within the pulse and time. The broadband pulsed light source device includes a divider that spatially divides the supercontinuous light emitted from the nonlinear element into light of various wavelength regions. The attenuation unit is a filter that attenuates the oscillation wavelength of the pulsed laser source in the light of each wavelength region after being segmented by the splitter. The stretching element consists of multiple optical fibers arranged side-by-side on the output side of the splitter. Each optical fiber is a fiber into which light is incident after being divided into different wavelength regions, and its length or dispersion characteristics vary depending on the wavelength region of the incident light.

15. The broadband pulsed light source device as described in claim 14, characterized in that, The divider is an arrayed waveguide diffraction grating.

16. A broadband pulsed light source device, characterized in that, have: Pulsed laser source; Nonlinear elements cause light from a pulsed laser source to produce a nonlinear effect, resulting in the emission of supercontinuum light. The attenuation unit attenuates the oscillation wavelength of the pulsed laser source contained in the supercontinuum light emitted from the nonlinear element. as well as A broadening element that broadens the pulse width of the supercontinuum light emitted from the nonlinear element in a one-to-one manner with respect to the wavelength of the light within the pulse and time. The attenuation unit is an arrayed waveguide diffraction grating, which, in a state where the oscillation wavelength of the pulsed laser source in the supercontinuum light emitted from the nonlinear element is attenuated, spatially divides the supercontinuum light into light in various wavelength regions. The stretching element is an optical fiber connected to each exit-side waveguide of the arrayed waveguide diffraction grating. The length or dispersion characteristics of each optical fiber vary depending on the wavelength range of the incident light.

17. The broadband pulsed light source device as described in claim 16, characterized in that, The oscillation wavelength of the pulsed laser source is located within the boundary wavelength region of the exit waveguide of the arrayed waveguide diffraction grating.

18. A spectrophotometer, characterized in that, have: The broadband pulsed light source device according to any one of claims 2 to 3, 12 to 17; A light receiver receives light from an object that has been illuminated by broadband pulsed light from the broadband pulsed light source device. as well as The processing unit converts the output signal from the photodetector into a spectrum.

19. A spectrophotometer, characterized in that, have: The broadband pulsed light source device according to claim 10 or 11; A light receiver receives light from an object that has been illuminated by broadband pulsed light from the broadband pulsed light source device. as well as The processing unit converts the output signal from the photodetector into a spectrum. The light receiver includes a first light receiver and a second light receiver. Light reflected from the dichroic mirror is incident on the first light receiver, and light that has passed through the dichroic mirror is incident on the second light receiver.

20. A spectrophotometric determination method, characterized in that, have: The light-receiving step involves a light receiver receiving light from an object irradiated with broadband pulsed light from the broadband pulsed light source device according to any one of claims 2 to 3, 12 to 17; and The conversion step uses the processing unit to convert the output signal from the photodetector into a spectrum.

21. A spectrophotometric determination method, characterized in that, have: The light-receiving step involves a light receiver receiving light from an object irradiated with broadband pulsed light from the broadband pulsed light source device of claim 10 or 11; and The conversion step uses the processing unit to convert the output signal from the photodetector into a spectrum. The light receiver includes a first light receiver and a second light receiver. Light reflected from the dichroic mirror is incident on the first light receiver, and light transmitted through the dichroic mirror is incident on the second light receiver. The light receiving step is a step in which the first light receiver and the second light receiver receive light. The conversion step is to use the arithmetic unit to convert the output signals from the first and second photodetectors into a spectrum.

22. A spectrophotometric analysis method, characterized in that, have: The light receiving step involves a light receiver receiving light from an object that has been irradiated with broadband pulsed light from the broadband pulsed light source device according to any one of claims 2 to 3, 12 to 17. as well as The process of analyzing an object involves using a processing unit to process the output signal from the light receiver and comparing it with a standard value. The intensity of the supercontinuum light emitted from the broadband pulsed light source device has a width of less than 3 dB.

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