JP5646095B1 - Measuring device - Google Patents

Abstract

There is provided a small light source device capable of arbitrarily selecting the wavelengths of two synchronized pulsed light having different wavelengths and sweeping them at high speed. A light source device according to an aspect of the present invention includes a light generating unit that emits first light and second light that are continuous lights and have different wavelengths, and first light and second light. , Respectively, to generate a first pulsed light and a second pulsed light; and a spectrum extending means for extending a spectral width of at least one of the first and second pulsed light; Pulse width compression means for compressing the pulse width of the at least one pulse light after the spectrum width is expanded, and at least one after the spectrum width is expanded and before or after the pulse width is compressed And a variable wavelength selecting means for emitting a pulse light component in a specific wavelength band that can be selected. [Selection] Figure 1

Description

  The present invention relates to a light source device that can be used in a measuring device such as a microscope using Raman scattering.

  Microscopes that use coherent anti-stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) have been proposed as microscopes that can observe the three-dimensional distribution and in vivo composition of biomolecules. ing. In these microscopes, the sample is irradiated with two synchronized pulse lights (optical pulse trains) having different wavelengths to induce CARS and SRS. At this time, in order to enable observation of various molecules and tissues, it is necessary to set an energy difference (wavelength difference) between the two pulse lights according to the vibration level of the molecules and tissues.

  Patent Document 1 discloses a method of generating two synchronized pulse lights having different wavelengths from each other by pulsing continuous light at a repetition frequency of a trigger signal. In this method, a broadband solid-state laser is used as a light source, and wavelength oscillation is performed by controlling the oscillation wavelength. Further, Patent Document 2 generates two synchronized pulse lights by pulsing continuous light with a signal from an external signal generator, and controls the repetition frequency of the external signal to synchronize the pulse light. A method of performing control is disclosed. This Patent Document 2 does not describe wavelength selection or wavelength sweeping methods.

WO2011 / 163353 JP 2009-80007 A

  In order to arbitrarily select or sweep the wavelength in a wide band, it is necessary to use a solid laser that is large in size and cannot be said to have good maintainability, as in the method disclosed in Patent Document 1. When a solid-state laser is used, it is necessary to control the inside of the resonator, such as the laser crystal angle, so that high-speed wavelength sweep cannot be performed.

  The present invention provides a small light source device capable of arbitrarily selecting the wavelengths of two synchronized pulsed light having different wavelengths and sweeping them at high speed.

A measuring apparatus according to one aspect of the present invention includes: a light generating unit that emits first and second continuous lights having different wavelengths; a signal generating unit that outputs first and second timing signals; Based on the multiplication means for multiplying one of the two timing signals, and the first and second timing signals obtained by multiplying the one timing signal . and expansion means for expanding a pulsing means for generating first and second pulse light by pulsing, at least the spectral width of one pulse beam of the first and second pulsed light, respectively, spectral width There selection means for extracting a compression means for compressing the pulse width of the expanded pulsed light, pulsed light component having a specific wavelength band from the pulsed light spectrum width is expanded, at least one of Light detecting means for the first and second pulsed light for detecting the light intensity modulated by the stimulated Raman scattering caused by irradiating the sample serial is a pulse light component having a specific wavelength band, and characterized in that it has a To do.

According to the present invention, with a small and simple configuration, two pulse lights irradiated to a sample to generate stimulated Raman scattering from two continuous lights, and one repetition frequency is a multiplication of the other repetition frequency. it is possible to generate two pulsed light is, optionally a wavelength band of at least one pulsed light can choose to Rukoto. For this reason, it is possible to realize a small measuring apparatus capable of performing good measurement using stimulated Raman scattering .

1 is a block diagram showing a configuration of a light source device that is Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating a configuration example of a pulse width compression element used in the light source device of the first embodiment. FIG. 6 is a diagram illustrating calculation results in the first embodiment. FIG. 6 is a diagram illustrating a calculation result in the first embodiment. The block diagram which shows the structure of the light source device which is Example 2 of this invention. FIG. 10 is a block diagram illustrating a modification of the light source device according to the second embodiment. The block diagram which shows the structure of the light source device which is Example 3 of this invention. FIG. 10 is a block diagram illustrating a modification of the light source device according to the third embodiment. The block diagram which shows the structure of the SRS microscope which is Example 4 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the structure of the light source device used for the SRS measuring device as a reference technical example (henceforth Example 1) of this invention is shown. In FIG. 1, reference numeral 101 denotes an external signal generator (SG). Reference numeral 102 denotes a first semiconductor laser (L1) whose oscillation wavelength is the first wavelength, and reference numeral 112 denotes a second semiconductor laser (L2) whose oscillation wavelength is the second wavelength. The first and second semiconductor lasers 102 and 112 constitute light generating means. Reference numerals 103 and 113 denote pulsing elements (IM: pulsing means), and reference numerals 104, 109, and 114 denote optical amplifiers (AMP). Reference numerals 105 and 115 denote spectrum expansion elements (SE: expansion means), and reference numerals 106 and 116 denote pulse width compression elements (PWC: compression means). Reference numeral 107 denotes a variable wavelength selection element (Tunable Bandpass Filter: hereinafter referred to as TBPF) as selection means, and reference numeral 108 denotes a control unit (BPC: control means) that controls the TBPF 107. Reference numeral 110 denotes a multiplexing unit (WC), and 111 denotes an electrical delay line (DL).

  The first semiconductor laser 102 emits first laser light as first light that is continuous light having a first wavelength, and the second semiconductor laser 112 emits second light that is continuous light having a second wavelength. As a second laser beam. The first laser beam and the second laser beam are guided to the pulse elements 103 and 113, respectively. The pulsing elements 103 and 113 respectively pulse the first laser light and the second laser light at a timing according to the timing signal output from the external signal generator 101, and the first pulse light and the second pulse light are pulsed. Produce light. The first and second pulse lights are amplified by the optical amplifiers 104 and 114, respectively, and enter the spectrum extending elements 105 and 115, respectively.

  Each of the spectrum extension elements 105 and 115 extends the spectrum width of the first and second pulse lights to a predetermined wide band. The first and second pulse lights whose spectral widths are expanded are incident on the pulse width compression elements 106 and 116. The pulse width compression elements 106 and 116 compress the pulse widths of the first and second pulse lights after the spectrum width is expanded. Then, the first pulse light after the spectrum width is expanded and the pulse width is compressed is incident on the TBPF 107. The TBPF 107 extracts and emits a pulsed light component in a specific wavelength band that is a selected extraction wavelength band from the incident first pulsed light. The specific wavelength band can be selected (changed) through the control unit 108. The pulse light component in the specific wavelength band is guided to the optical amplifier 109. The optical amplifier 109 amplifies the light intensity attenuated by the wavelength extraction (wavelength selection) by the TBPF 107.

  The pulse light component of a specific wavelength band (hereinafter also referred to as the first pulse light) that has passed through the pulse width compression element 106, the TBPF 107, and the optical amplifier 109, and the second pulse light that has passed through the pulse width compression element 116 are combined. The light is synthesized (combined) coaxially in the unit 110 and emitted from the light source device.

  The optical paths from the first and second semiconductor lasers 102 and 112 to the multiplexing unit 110 are all formed by optical fibers, and all of these optical fibers are polarized in order to ensure stability as a light source device. A holding fiber is preferred. However, an optical fiber that is not a polarization maintaining type may be used, or it may be used in combination with a polarization controller.

  The first and second semiconductor lasers 102 and 112 emit monochromatic continuous light corresponding to the first and second wavelengths, respectively. For example, when the light source device of this embodiment is used for a CARS microscope or an SRS microscope, the first and second wavelengths may be selected so that the difference between them roughly matches the vibration level of the molecule to be observed. . As the first and second semiconductor lasers 102 and 112, a general laser diode, a quantum dot laser, a quantum cascade laser, or the like can be used.

  The pulse elements 103 and 113 are constituted by intensity modulators, and are selected according to the first wavelength and the second wavelength, respectively. By using a general intensity modulator as the pulse elements 103 and 113, continuous light can be pulsed into optical pulses having a pulse width of up to several tens of ps (picoseconds). A timing signal for controlling the repetition frequency at which the pulse elements 103 and 113 pulse continuous light is supplied from the external signal generator 101. By changing the repetition frequency of the timing signal in the external signal generator 101, the repetition frequency of the first and second pulsed light emitted from the pulse elements 103 and 113 is controlled. As the pulse elements 103 and 113, an LN (Lithium Niobate) modulator, an electroabsorption optical modulator, or the like can be used.

  The optical amplifiers 104 and 114 compensate for the insertion loss in the pulse elements (intensity modulators) 103 and 113, and amplify the intensity of the pulsed light to the required intensity in the next spectrum expansion elements 105 and 115. As the optical amplifiers 104 and 114, an optical fiber amplifier using a gain medium as an optical fiber to which a rare earth such as ytterbium Yb or erbium Er is added can be used. In order to ensure the stability as the light source device, it is preferable to use an optical amplifier composed of a polarization maintaining optical fiber. Moreover, it is good also as an amplifier of a multistage structure as needed.

  The spectrum expansion element 105 on which the first pulse light amplified by the optical amplifier 104 is incident is a highly nonlinear fiber (hereinafter referred to as HNLF), and the spectrum width of the pulse light is expanded to a wide band by a nonlinear optical effect. To do. The upper limit of the spectrum extension is about the gain band of the optical amplifier 104 being used. The spectrum extending element 105 that extends the spectrum in a wide band as described above may be a long-distance single mode fiber (hereinafter referred to as SMF), a photonic crystal fiber, a liquid core fiber, or the like. A fiber having higher nonlinearity can shorten the fiber length, so that a more compact and stable system can be configured.

  The spectral expansion element 115 on which the second pulse light amplified by the optical amplifier 114 is incident is SMF, and expands the spectral width of the optical pulse by a nonlinear optical effect as in the spectral expansion element 105. However, spectrum expansion by SMF is not for the purpose of widening the band, but for pulse width compression. For example, when the light source device of this embodiment is used for a CARS microscope or an SRS microscope, the pulse width is preferably about several to 10 ps in order to improve the wave number resolution. Therefore, the pulse width when pulsed by the intensity modulator is further increased. It needs to be compressed. From the uncertainty principle, it is necessary to extend the spectrum for pulse width compression. Since the spectrum expansion width is about 0.1 to 1 nm, the fiber does not have to be highly nonlinear.

  The pulse width compression elements 106 and 116 are configured by combining a circulator and a chirped fiber Bragg grating (hereinafter referred to as CFBG). The CFBG is a fiber type diffraction grating that reflects at different positions depending on the wavelength of incident pulsed light, and the pulse width can be compressed by applying a chirp opposite to the chirp of the incident pulsed light.

  FIG. 2 shows a configuration example of each pulse width compression element. 201 is a circulator and 202 is CFBG. The pulsed light incident on the circulator 201 is guided to the CFBG 202 and the pulse width is compressed by the CFBG 202. The pulsed light whose pulse width is compressed returns to the circulator 201 and is emitted from the pulse width compression element.

  The pulse width compression element 106 compresses the pulse width of the first pulsed light to several hundred fs (femtoseconds) to several ps or less in order to reduce the timing shift for each wavelength at the time of wavelength selection. The pulse width compression element 116 compresses the pulse width of the second pulse light to about several to 10 ps. In this embodiment, CFBG is used as the pulse width compression element, but a dispersion compensating optical fiber, a prism pair, a diffraction grating pair, or the like may be used.

  The TBPF 107 transmits and extracts only a pulsed light component of a specific wavelength band selected from the first pulsed light whose spectrum is expanded to a wide band (the pulse width is also compressed in this embodiment). As the TBPF 107, commonly used ones such as a diffraction grating and a slit, an acousto-optic variable wavelength filter, a waveguide type diffraction grating, and an FBG can be used. For example, when the light source device of this embodiment is used for a CARS microscope or an SRS microscope, the pulse width is preferably several to 10 ps in order to improve the wave number resolution, so that the wavelength width of the specific wavelength band to be selected is 0.5. About 1 nm is preferable. Since the pulse width compression element 106 and the TBPF 107 function linearly, it is possible to change their front-rear arrangement. That is, a pulse light component in a specific wavelength band may be extracted by the TBPF 107 from the first pulse light before the pulse width by the pulse width compression element 106 is compressed. In this case, the pulse width compression element 106 functions as a delay compensation element that compensates for a relative time delay for each wavelength.

  The control unit 108 is configured by a computer and controls a specific wavelength band extracted by the TBPF 107. For example, when a diffraction grating and a slit are used as the TBPF 107, the control unit 108 drives a movable stage that holds the slit to control the position and sweep speed of the slit with respect to the diffraction grating. By continuously changing the specific wavelength band, the wavelength sweep of the first pulsed light extracted by the TBPF 107 can be performed.

  As described above, the optical amplifier 109 amplifies the light intensity attenuated by the wavelength extraction by the TBPF 107 to a predetermined light intensity. The optical amplifier 109 may have a multistage configuration as necessary.

  The electrical delay line 111 gives a time delay amount to the timing signal output from the external signal generator 101 and input to the pulse forming element 113, so that the timing between the first pulse light and the second pulse light is reached. The deviation (hereinafter referred to as pulse timing) is electrically adjusted. When the pulse timing deviation is large, a delay line with a fixed time delay amount may be added. The deviation in pulse timing may be detected directly by a detector such as an oscilloscope or a high-speed streak camera. Indirect by a method such as a cross-correlation method (for example, by condensing two-wavelength pulse light on a semiconductor sensor capable of detecting two-photon absorption to detect a pulse timing shift state of the two-wavelength pulse light). May be detected automatically. The first and second pulse lights can be synchronized with each other by adjusting the delay amount of the electrical delay line 111 according to the detected deviation of the pulse timing.

  The multiplexing unit 110 is composed of a wavelength multiplexing coupler and multiplexes the first and second pulse lights coaxially. When the first and second pulse lights are spatially output, the multiplexing unit 110 does not need to be a fiber coupler. In other words, a fiber collimator may be attached to the end of the outgoing fiber of these pulsed lights, and the first and second pulsed lights may be spatially output, and then these may be coaxially combined via a dichroic mirror or the like. Further, when it is not necessary to multiplex the signals coaxially, there is no need for a means for making them coaxial.

  Hereinafter, specific numerical examples in the present embodiment will be shown. In the following numerical example, assuming the pulse width and spectrum after pulsing, the optical pulse after the optical intensity is amplified by the optical amplifier is broadened and compressed, and a process until a specific wavelength band is selected. The calculation was performed. The fiber propagation follows the nonlinear Schroedinger equation of equation (1) and was calculated using the split step Fourier method. The effect of propagation in the optical fiber provided between the elements was ignored.

Where A is the envelope function of the optical pulse, z is the optical axis direction coordinate, α is the propagation loss, β ₂ is the group velocity dispersion, β ₃ is the third order dispersion, T is the time, γ is the nonlinear coefficient, and ω ₀ is frequency, _{T R} denotes a delay Raman response.
First, calculation results for the line from the first semiconductor laser 102 to the TBPF 107 will be shown. The wavelength of the first semiconductor laser 102 is 1560 nm, and the output average power is 20 mW. A semiconductor laser whose output from the visible light region to the near infrared region is about several to several hundred mW is easily available. The pulsing in the pulsing element 103 is performed at a repetition frequency of 40 MHz. Referring to Document A below, pulse width of 55 ps can be obtained by FWHM (Full Width of Half Maximum) using an intensity modulator, so that the pulse width after pulsing is 55 ps. Further, it is assumed that the pulsed light after being pulsed by the optical amplifier 104 is amplified to a peak power of 460 W. This amplification can be realized by configuring the optical amplifier 104 in a two-stage configuration and amplifying each by about 20 dB. FIG. 3A shows the pulse waveform and spectrum of the amplified pulsed light. The pulse waveform and spectrum were of the sech type, and the chirp at the time after amplification was ignored.
(Reference A) “Fiber delivered two-color picosecond source through nonlinear spectral transformation for coherent Raman scattering imaging”, Appl. Phys. Lett. 100, 071106 (2012).

As the spectrum expansion element 105, HNLF having the following specifications was used. FIG. 3B shows the calculation result of the pulse waveform and spectrum when the amplified pulsed light is transmitted. By passing through the spectral extension element 105, the spectral width is extended to about 50 nm (about 207 cm ⁻¹ ).
Fiber length L = 125m
Propagation loss α = 0.63 dB / km
Dispersion parameter D = 0.04 ps / km / nm
Dispersion slope Sl = 0.03 ps / km / nm ²
Effective core area A _eff = 10 μm ²
Delayed Raman coefficient T _R = 0.005 ps.

  FIG. 3C shows a pulse waveform after pulse width compression when the dispersion parameter in the CFBG 202 in the pulse width compression element 106 is 0.39 ps / nm. Due to the pulse width compression performed by the pulse width compression element 106, the pulse width is about 2.7 ps in FWHM. At this time, the nonlinear effect in the circulator 201 and the CFBG 202 was ignored.

  FIG. 3D shows a pulse waveform and spectrum when the specific wavelength band in the TBPF 107 is about 1559.5 to 1560.5 nm. At this time, the pulse width was calculated by Fourier transform of the spectrum. In FIG. 3D, a double pulse is used. However, when the light source device of this embodiment is used for a CARS microscope or an SRS microscope, only synchronized two-wavelength pulsed light contributes to scattering, and thus is several tens of ps away. The front pulse is not a problem. The specific wavelength band shown in FIG. 3D is merely an example, and the same pulse waveform and spectrum can be obtained even when another specific wavelength band is selected. Further, by continuously changing the specific wavelength band, it is possible to perform wavelength sweeping over the entire wavelength range of the pulsed light incident on the TBPF 107.

  With the above configuration, first pulsed light having a spectrum selection (sweep) width of about 50 nm and a pulse width of about 7 ps can be obtained by FWHM.

  Next, calculation results for the line from the second semiconductor laser 112 to the pulse width compression element 116 are shown. The wavelength of the second semiconductor laser 112 is 1064 nm, and the output average power is 30 mW. Further, pulsing in the pulsing element 113 is performed at a repetition frequency of 40 MHz, and the pulse width after pulsing is 55 ps. In addition, the optical pulse after being pulsed by the optical amplifier 114 is amplified to a peak power of 460 W. FIG. 4A shows the pulse waveform and spectrum of the amplified optical pulse.

As the spectrum expansion element 115, SMF having the following specifications was used. FIG. 4B shows the calculation result of the pulse waveform and spectrum when the amplified optical pulse is transmitted. By passing through the spectral extension element 115, the spectral width is extended to about 0.5 nm.
Fiber length L = 16m
Propagation loss α = 0.55 dB / km
Dispersion parameter D = 27.14 ps / km / nm
Dispersion slope S1 = 0.173 ps / km / nm ²
Effective core area A _eff = 80 μm ²
Delayed Raman coefficient T _R = 0.005 ps.

  FIG. 4C shows a pulse waveform after pulse width compression when the dispersion parameter in the CFBG 202 in the pulse width compression element 116 is 70 ps / nm.

  With the above configuration, second pulsed light having a pulse width of about 4.6 ps can be obtained by FWHM.

When the light source device of this embodiment is used for a CARS microscope or an SRS microscope, a wave number resolution of 8 cm ⁻¹ and a sweep width of about 207 cm ⁻¹ are possible by pulsing with the two lines described above. By broadening both lines or increasing the number of lines in different wavelength bands, it is possible to select and sweep a wider wave number.

  Although one numerical example is shown here, a desired output pulse width, by appropriately setting numerical values and configurations such as the wavelength of other semiconductor lasers, output, fiber parameters, dispersion in CFBG, gain of an optical amplifier, etc. A light source device having a spectrum and a wavelength variable width can be configured.

  In this embodiment, the case where an intensity modulator is used as a pulsing element and pulsing is performed by external modulation has been described. However, pulsing means for pulsing by directly modulating a semiconductor laser by gain switching or the like. May be used. In addition, when the wavelength difference between the first and second pulse lights may be as small as about half or less (about 30 nm) of the gain bandwidth of the optical amplifier, one semiconductor laser is used, and these are divided into two lines. You may branch and use. In this case, the semiconductor laser and the two branch lines constitute a light generating means, and the continuous light emitted from one of the two branch lines becomes the first laser light, and the continuous light emitted from the other is the second. It becomes this laser beam.

  According to the present embodiment, it is possible to realize a small light source device that stably generates two-wavelength pulsed light capable of wavelength sweeping. And by using this light source device for CARS and an SRS microscope (measuring device), a molecular vibration spectrum (Raman spectrum) in a wide band can be detected well.

Next, a description will be given of a light source device used in the SRS measuring apparatus according to the first embodiment (hereinafter referred to as Embodiment 2) of the present invention. In this embodiment, the repetition frequency of one of the first and second pulse lights is multiplied with respect to the repetition frequency of the other pulse light. As shown in FIG. 5, the configuration as the light source device is obtained by adding a multiplication unit (multiplication means) 1011 to the configuration of the light source device of the first embodiment (FIG. 1). In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description is omitted.

  The multiplier 1011 is configured by a frequency multiplier such as a frequency doubler, a frequency tripler, or a frequency multiplier. The multiplier 1011 multiplies the repetition frequency of the timing signal input to the pulse element 113. As a result, the repetition frequency of the second pulsed light that is the one pulsed light is multiplied with respect to the repetition frequency of the first pulsed light that is the other pulsed light.

For example, referring to the following document B, the SNR (Signal to Ratio) of the SRS microscope can be improved by doubling the repetition frequency of one pulsed light. This is because the lock-in detection frequency can be maximized when detecting the SRS signal from the sample in the SRS microscope.
(Reference B) "Stimulated Raman scattering microscope with shot noise limited sensitivity using subharmonically synchronized laser pulses", Optics Express, Vol. 18, Issue 13, pp. 13708-13719 (2010).

  In the present embodiment, the case of electrically multiplying the repetition frequency such as a frequency doubler has been described. However, as shown in FIG. 6, an optical delay line using an optical fiber and a coupler is used as a multiplier 1011 ′ for pulsing. You may insert between the element 113 and the optical amplifier 114. FIG.

  According to the present embodiment, in a measuring apparatus such as a biological microscope, a compact light source device having a simple configuration, having a repetition frequency ratio advantageous for lock-in detection, and capable of emitting two-wavelength pulsed light that can be swept in wavelength. Can be realized.

Next, a description will be given of a light source device used in an SRS measuring apparatus that is a second embodiment (hereinafter referred to as a third embodiment) of the present invention. In the present embodiment, the first and second pulse lights are detected by detecting a difference in pulse timing (relative time difference) and adjusting the time delay amounts of the first and second pulse lights. Control is performed to synchronize pulsed light (hereinafter collectively referred to as two-wavelength pulsed light). In FIG. 7, the structure of the light source device of a present Example is shown. In the present embodiment, a pulse timing detection unit (PTD: time difference detection unit) 1203 and a synchronization control unit (SC: synchronization control unit) 1204 are added to the configuration of the second embodiment shown in FIG. In the present embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals as those in the second embodiment, and the description is omitted.

  A fiber collimator 1201 outputs the output of the optical fiber to the space as parallel light. An objective lens 1202 focuses the two-wavelength pulsed light on a pulse timing detection unit 1203 that detects a pulse timing shift of the two-wavelength pulsed light. In order to detect a pulse timing shift, a waveform indicating a cross-correlation such as two-photon absorption in two-wavelength pulsed light may be used. Since the cross-correlation waveform generates a stronger peak as the wavelengths of the two-wavelength pulses overlap, it can be used as an index for evaluating the pulse timing deviation of the two-wavelength pulse light.

  The pulse timing detection unit 1203 is low in sensitivity to a two-photon absorption wavelength band generated only by each pulse light among photodiodes made of a semiconductor such as Si or InGaAs, for example, and is sensitive to a two-photon absorption wavelength between two wavelength pulse lights. The one with a higher value may be selected and used.

  The synchronization control unit 1204 controls the delay amount of the electrical delay line 111 so that the value of the electrical signal output from the pulse timing detection unit 1203 is constant, that is, the pulse timing shift is reduced. With such a configuration, it is possible to reduce the pulse timing deviation of the two-wavelength pulsed light.

  In FIG. 8, the structure of the modification of a present Example is shown. In this modified example, synchronization control of the two-wavelength pulse light is not performed by adjusting the electrical delay, but synchronization control is performed by adjusting the optical delay using the optical delay line (OD) 1301.

  The optical delay line 1301 is provided with a piezo stage or the like in an air gap variable delay line, and coarsely adjusts the amount of time delay given to the second pulse light at a low speed over a wide range. The phase modulator (PM) 1302 finely adjusts the amount of time delay given to the second pulse light at high speed by applying phase modulation to the second pulse light. The optical delay line 1301 and the phase modulator 1302 complementarily perform synchronization control according to the feedback signal from the synchronization circuit 1204. It should be noted that only the optical delay line 1301 may be provided, or the electric delay line 111 may be changed to perform synchronization control.

  According to the present embodiment, it is possible to realize a small wavelength-swept light source device that can stably emit pulsed light having different wavelengths.

  In each of the above embodiments, the case where the spectrum expansion elements 105 and 115 and the pulse width compression elements 106 and 116 are provided for the first and second pulse lights has been described. However, the spectrum expansion element and the pulse width compression element may be provided only for at least one of the first and second pulse lights (pulse light whose wavelength is selected by the TBPF 107). In each of the above embodiments, the case where the TBPF 107 is provided only for the first pulse light has been described. However, the TBPF may be provided for each of the first and second pulse lights.

  In the present embodiment, an SRS microscope as a measuring device using the light source device described in any of Embodiments 1 to 3 as a light source unit will be described. When the sample is irradiated with two-wavelength pulsed light having a frequency difference (wavelength difference) that resonates with the vibration of the molecule to be observed contained in the sample, and the molecule is forced to vibrate, the short wavelength side of the two-wavelength pulsed light This causes a phenomenon in which the energy of the pulsed light decreases and the energy of the pulsed light on the long wavelength side increases. This is SRS. The SRS microscope performs high-contrast and high-sensitivity molecular vibration imaging by detecting the increase or decrease in the energy of the pulsed light. In addition, the Raman spectrum can be acquired by sweeping the wavelength difference between the two-wavelength pulses, and the tissue structure and composition of the sample can be specified. FIG. 9 shows the configuration of the SRS microscope. This SRS microscope detects a decrease in energy of pulsed light on the short wavelength side.

  In FIG. 9, reference numeral 1401 denotes the light source device described in any one of the first to third embodiments. Reference numeral 1402 denotes a fiber collimator, and reference numeral 1403 denotes a scanning device (scanning means) that two-dimensionally scans a sample with two-wavelength pulsed light. Reference numeral 1404 denotes an objective lens (objective optical system), and 1405 denotes a sample stage on which a sample is set and its position is adjusted. 1406 is a condenser lens, 1407 is a mirror, and 1408 is a wavelength filter. Reference numeral 1409 denotes a sensor, and reference numeral 1410 denotes a lock-in detection device that detects lock-in of an output signal of the sensor 1409. The sensor 1409 and the lock-in detection device 1410 constitute a light detection means. Reference numeral 1411 denotes an image processing device (processing means) that processes (analyzes and images) the output signal of the lock-in detection device 1410 and displays the generated image.

  The light source device 1401 emits two-wavelength pulsed light (first and second pulsed light) having a repetition frequency of 1: 2. The energy (wavelength) difference between the two-wavelength pulsed light is set so as to substantially match the vibration level of the molecule to be observed in the sample. A fiber collimator 1402 is attached to the tip of the optical fiber that combines the two-wavelength pulsed light, and the two-wavelength pulsed light output from the fiber collimator 1402 to the space is guided to the scanning device 1403.

  The scanning device 1403 is composed of a biaxial galvanometer mirror, and two-dimensionally scans the sample at the condensing point of the two-wavelength pulsed light. A resonant mirror may be used instead of the galvanometer mirror.

  The objective lens 1404 condenses the two-wavelength pulsed light toward the sample, and the condensing lens 1406 condenses the light transmitted through the sample.

  In order to prevent the peripheral portion of the displayed image from becoming dark, the mirror surface of the scanning device 1403 and the exit pupil surface of the objective lens 1404 have a conjugate relationship so that the light amount distribution on the sample during scanning is uniform. A relay lens pair (scanning optical system) may be provided. In order to reduce artifacts, it is preferable to set the numerical aperture NA (Numerical Aperture) of the condenser lens 1406 to be larger than the NA of the objective lens 1404.

  The sample stage 1405 can perform coarse movement and fine movement in the horizontal biaxial direction and the vertical direction. After a sample sandwiched between a slide glass and a cover glass is placed on the sample stage 1405, the sample stage 1405 is driven and the sample is moved to a two-dimensional scanning region by the scanning device 1403.

  The mirror 1407 reflects the light from the condenser lens 1406 and guides it to the sensor 1409. The wavelength filter 1408 transmits only the wavelength band of the pulsed light having the higher repetition frequency out of the two-wavelength pulsed light. The sensor 1409 is composed of a photodetector and converts the received pulsed light into an electrical signal. In order to collect light efficiently with respect to the light receiving portion of the sensor 1409, a condensing lens may be disposed in front of the sensor 1409.

  The lock-in detection device 1410 is configured by a so-called lock-in amplifier, and detects the lock-in of the output signal from the sensor 1409 at a frequency that is half the repetition frequency of the pulsed light that has passed through the wavelength filter 1408. In order to reduce noise, a band-pass filter that removes frequency components other than the repetitive frequency band to be detected may be arranged in front of the lock-in detection device 1410.

  The image processing apparatus 1411 is constituted by a personal computer, analyzes a signal detected by lock-in to form a two-dimensional image, and then displays the image on a display.

  As shown in FIG. 9, the image processing device 1411 may be used as a control device for the scanning device 1403 and the sample stage 1405.

  As described above, by using any one of the light source devices of Examples 1 to 3, it is possible to realize an SRS microscope that can downsize the entire microscope and stably perform molecular vibration imaging. Further, by sweeping the wavelength of the two-wavelength pulsed light in the light source device, spectral information of the sample can be obtained in a wider wavelength band.

  In the present embodiment, the case where the light source device described in any one of Embodiments 1 to 3 is used for the SRS microscope has been described. However, the light source device may be a CARS microscope, an endoscope, or the like that uses two-wavelength pulsed light. It can also be used for a measuring device.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

102, 112 Semiconductor lasers 103, 113 Pulse conversion elements 105, 115 Spectral expansion elements 106, 116 Pulse width compression elements 107 Variable wavelength selection elements

Claims (16)

Light generating means for emitting first and second continuous lights having different wavelengths from each other;
Signal generating means for outputting first and second timing signals;
A multiplier for multiplying one of the first and second timing signals;
Said one of the timing signals to generate first and second pulse light by pulsing each of said first and second continuous light on the basis of the the multiplied of the first and second timing signal Pulsing means;
And expansion means for expanding the spectrum width of at least one of the pulsed light of said first and second pulse light,
Compression means for compressing the pulse width of the pulsed light having an extended spectral width;
Selection means for extracting a pulsed light component of a specific wavelength band from the pulsed light having an extended spectrum width;
A light detection means for detecting light whose intensity is modulated by stimulated Raman scattering generated when the first and second pulse lights, at least one of which is a pulse light component of the specific wavelength band, are irradiated on the sample;
A measuring apparatus comprising: The measuring apparatus according to claim 1, further comprising a control unit that changes the specific wavelength band. The measuring apparatus according to claim 1 , wherein the light generating unit includes first and second semiconductor lasers that emit first and second continuous lights, respectively . Measurement device according to any one of claims 1 to 3, characterized in that it has an electrical delay line to provide a time delay to said first or second timing signal. The measurement apparatus according to claim 4, further comprising a synchronization control unit that reduces a timing shift between the first and second pulse lights by controlling the time delay amount. According to any one of claims 1 to 3, characterized in that it comprises a first and second pulse light synchronization control means for mutually synchronizing the first and second pulse light on the basis of the relative time difference Measuring device. The measuring apparatus according to claim 6 , further comprising a time difference detecting unit that detects the relative time difference. The measuring device according to any one of claims 1 to 7 , wherein the expansion unit is configured by a single mode fiber, a highly nonlinear fiber, a photonic crystal fiber, or a liquid core fiber. Measurement apparatus according to any one of claims 1 to 8, the spectral width and having an optical amplifier for amplifying the intensity of the expanded pulsed light. The measuring apparatus according to claim 9 , wherein the optical amplifier includes a polarization maintaining optical fiber. 11. The measuring apparatus according to claim 1, further comprising a multiplexing unit that synthesizes the second pulsed light and the pulsed light component. Said light detecting means includes a sensor for receiving light from the sample, to any one of claims 1 to 11, characterized in that it comprises a lock-in amplifier, a lock-in detection output signal of the sensor The measuring device described. A control means for changing the specific wavelength band, by performing wavelength sweeping of the pulse light component to be irradiated on the sample by the control means, from claim 1, characterized in that to obtain the Raman spectrum 12 of the The measuring device according to any one of the above. The measuring device according to any one of the first and second claims 1 to 13, characterized in that it comprises a scanning means for scanning the sample with pulsed light. Measurement apparatus according to any one of claims 1 to 14, characterized in that it comprises a processing means for processing the output signal of the light detecting means. The measurement apparatus according to claim 15 , wherein the processing unit displays an image generated based on an output signal from the light detection unit.