Pulse compression device, optical system, optical device, and pulse compression method

Abstract

This pulse compression device 40 compensates for dispersion of introduced pulsed light in an optical path through which the pulsed light having a wavelength range expanded by passing through a hollow fiber is introduced and then led out. The pulse compression device 40 comprises: a spectroscopic element 42; and a deformable mirror 44. The spectroscopic element 42 spectrally disperses the pulsed light so as to make the optical path different according to a wavelength. The deformable mirror 44 has a reflecting surface for reflecting the spectrally dispersed pulsed light, and can deform the reflecting surface such that the length of the optical path changes in accordance with the position in the reflecting surface.

Description

Pulse compression device, optical system, optical device, and pulse compression method

[0001] The present invention relates to a pulse compression device, an optical system, an optical apparatus, and a pulse compression method.

[0002] Optical systems that use pulsed light are known. For example, an optical system is a multiphoton excitation microscope that observes the inside of a living organism by exciting a fluorescent dye introduced into the organism with pulsed light. In a multiphoton excitation microscope, the efficiency of excitation of the fluorescent dye by a multiphoton process of two or more photons increases as the pulse width, which is the time from when the intensity of the pulsed light exceeds a threshold until when it falls below the threshold, becomes shorter. For example, if the threshold is half the maximum intensity of the pulsed light, the pulse width is expressed as the full width at half maximum. For example, there is anticipation for the development of a device using multiphoton excitation with pulsed light having a wavelength of 1 [μm] to 2 [μm], which has high transmittance to biological materials (in other words, ultrashort pulsed light with a pulse width of a few femtoseconds). Thus, in optical systems that use pulsed light, it is sometimes necessary to shorten the pulse width.

[0003] Incidentally, if the wavelength range of the pulsed light is not sufficiently wide, the pulse width cannot be made sufficiently short (in other words, narrow) because the wavelength range and pulse width have a Fourier transform relationship. For this reason, for example, the optical system described in Patent Document 1 comprises a hollow fiber and a pulse compression device. Pulsed light introduced from a laser pulse light source passes through the hollow fiber. As a result, self-phase modulation occurs in the pulsed light, which expands the wavelength range of the pulsed light and causes dispersion. Also, the shorter the pulse width, the wider the wavelength range. A wide wavelength range may include light of undesirable wavelengths, but there is also the problem that it is not easy to remove any unwanted wavelength range while maintaining pulsed light with a narrow pulse width.

[0004] The pulse compression device reflects the pulsed light by at least one chirp mirror in the optical path from the introduction to the de-extraction of pulsed light whose wavelength range has been extended by passing through a hollow fiber, in order to compensate for the dispersion of the introduced pulsed light.

[0005] Japanese Patent Publication No. 2010-511296

[0006] By the way, dispersion occurs when pulsed light passes through a hollow fiber. However, it is difficult to compensate for the dispersion of pulsed light with a wide wavelength range and a narrow Fourier limit width (for example, pulsed light with a Fourier limit width of 6 [fs] or less) with high precision using only a chirped mirror. Therefore, in the above pulse compression device, there was a possibility that the pulse width could not be made sufficiently short.

[0007] One of the objects of the present invention is to make the pulse width sufficiently short.

[0008] On one side, the pulse compression device is a device that compensates for the dispersion of the introduced pulsed light in the optical path through which the pulsed light with an extended wavelength range passes through the hollow fiber and is led out.

[0009] The pulse compression device includes a spectroscopic element that splits the pulsed light so that the optical path varies according to the wavelength, and a deformable mirror that has a reflecting surface that reflects the split pulsed light and is deformable so that the length of the optical path changes according to the position within the reflecting surface.

[0010] On another side, the pulse compression method is a method that compensates for the dispersion of the introduced pulsed light in the optical path through which the pulsed light with an extended wavelength range passes through the hollow fiber and is led out.

[0011] The pulse compression method includes deforming the reflecting surface so that the length of the optical path changes according to the position within the reflecting surface that reflects the pulsed light, splitting the pulsed light so that the optical path varies according to the wavelength, and causing the split pulsed light to be incident on the reflecting surface.

[0012] In another aspect, the optical system comprises a hollow fiber through which pulsed light is introduced and which expands the wavelength range of the introduced pulsed light as it passes through the hollow fiber, and a pulse compressor that compensates for the dispersion of the introduced pulsed light in the optical path from the time the pulsed light, whose wavelength range has been expanded as it passes through the hollow fiber, is introduced until it is extracted.

[0013] The pulse compression device comprises a spectroscopic element that spectrally separates pulsed light so that the optical path differs according to the wavelength, and a deformable mirror having a reflective surface that reflects the spectrally separated pulsed light, and the reflective surface can be deformed so that the length of the optical path changes depending on the position within the reflective surface.

[0014] In another aspect, the pulse compression device includes wavelength component suppression means for suppressing components having wavelengths within a predetermined suppression range.

[0015] By providing wavelength component suppression means at a predetermined position within the pulse compression device, it is possible to easily obtain narrow-width pulsed light from which light in any unwanted wavelength range has been removed.

[0016] The pulse width can be made sufficiently short. Furthermore, it is possible to obtain narrow-width pulsed light by removing light in any unwanted wavelength range.

[0017] This is a block diagram showing the configuration of the optical system of the first embodiment. This is a diagram showing the configuration of the pulse compression device of the first embodiment. This is a spectrum showing the change in the intensity of pulsed light derived from the pulse compression device with respect to wavelength. This is an intensity waveform showing the change in the intensity of pulsed light with respect to delay time. This is a spectrum showing the change in fluorescence intensity with respect to wavelength when a fluorescent dye encapsulated in a protein is excited by pulsed light.

[0018] Hereinafter, embodiments of the pulse compression device, pulse compression method, and optical system of the present invention will be described with reference to Figures 1 to 5.

[0019] <First Embodiment> (Summary) The pulse compression device of the first embodiment compensates for the dispersion of introduced pulsed light in the optical path from the time the pulsed light, whose wavelength range has been extended by passing through a hollow fiber, is introduced until it is taken out. The pulse compression device comprises a spectroscopic element and a deformable mirror (in other words, a shape-changing mirror). The spectroscopic element spectrally separates the pulsed light so that the optical path differs according to the wavelength. The deformable mirror has a reflective surface that reflects the spectrally separated pulsed light, and the reflective surface can be deformed so that the length of the optical path changes depending on the position within the reflective surface.

[0020] According to this, the dispersion of pulsed light can be compensated with high precision. As a result, the pulse width can be made sufficiently short. Next, the optical system including the pulse compression device of the first embodiment will be described in more detail.

[0021] (Configuration) As shown in Figure 1, the optical system 1 comprises a laser pulse light source 10, an optical parametric amplifier 20, a hollow fiber 30, and a pulse compression device 40. In this example, the optical system 1 constitutes part of a multiphoton excitation microscope. The optical system 1 may also constitute part of an optical CT (Computed Tomography) device or a laser processing device.

[0022] The laser pulse light source 10 repeatedly generates pulsed light, which is light in a pulsed form. In this example, the laser pulse light source 10 is a titanium-sapphire regenerative amplifier. For example, the titanium-sapphire regenerative amplifier may be a Spifire Pro 35F manufactured by Spectraphysics ("Spectraphysics" is a registered trademark).

[0023] In this example, the pulse width, wavelength, and repetition frequency of the pulsed light generated by the laser pulse light source 10 are 35 [fs], 800 [nm], and 1 [kHz], respectively. The pulse width is the time from when the intensity of the pulsed light exceeds a threshold until it falls below the threshold. For example, the threshold may be half of the maximum intensity of the pulsed light. In this case, the pulse width may be expressed as the full width at half maximum. The repetition frequency is the number of times pulsed light is generated per second. Note that the laser pulse light source 10 may be a light source other than a titanium-sapphire regenerative amplifier.

[0024] The optical parametric amplifier 20 receives pulsed light generated by the laser pulse light source 10. The optical parametric amplifier 20 uses the introduced pulsed light as signal light (in other words, seed light) and generates idler light by amplifying it with pump light. In this example, the wavelength of the idler light is 1700 nm.

[0025] The optical parametric amplifier 20 outputs pulsed light, which is the generated idler light. Alternatively, the optical parametric amplifier 20 may output signal light instead of idler light. Furthermore, the optical system 1 does not necessarily need to include the optical parametric amplifier 20. In this case, the pulsed light generated by the laser pulse light source 10 is introduced into the hollow fiber 30.

[0026] The hollow fiber 30 has a hollow cylindrical cladding portion and a core portion surrounded by the cladding portion (in other words, constituting the internal space of the cladding portion). The core portion is filled with a dispersion medium. In this example, the dispersion medium is a gas. In this example, the gas filling the core portion is krypton (Kr). However, the gas filling the core portion may be a noble gas other than krypton (for example, argon (Ar), etc.).

[0027] The core section receives pulsed light derived from the optical parametric amplifier 20. The cladding section confines the pulsed light to the core section by reflecting the pulsed light that leaks out of the core section.

[0028] With this configuration, the hollow fiber 30 causes self-phase modulation in the pulsed light as it passes through. This expands the wavelength range of the pulsed light and also causes dispersion (in other words, group delay).

[0029] Incidentally, near-infrared light has a relatively high transmittance to substances that make up living organisms (in other words, biomolecules). For example, biomolecules include proteins. For this reason, near-infrared light is expected to be used as a probe to observe the inside of living organisms by penetrating the skin and other tissues. Two-photon microscopes that use pulsed light with a pulse width of approximately 100 fs, in addition to near-infrared light, are known.

[0030] However, conventionally used pulsed light with a wavelength of 800 nm does not have sufficiently high transmittance to biological materials. Therefore, it is hoped that pulsed light with a wavelength longer than 800 nm, specifically 1 μm to 2 μm, will be used to achieve higher transmittance to biological materials.

[0031] The efficiency of exciting fluorescent dyes by multiphoton processes involving two or more photons increases as the pulse width decreases (in other words, as the peak value of the electric field increases). On the other hand, if the wavelength range of the pulsed light is not sufficiently wide, the pulse width cannot be made sufficiently short.

[0032] In this example, the size of the hollow fiber 30 and the pressure of the gas filling the core are set so that the wavelength range of the pulsed light derived from the hollow fiber 30 is between 1.2 [μm] and 2.2 [μm]. In this example, the pulse width of the pulsed light derived from the hollow fiber 30 is approximately 50 [fs].

[0033] The pulse compression device 40 receives pulsed light whose wavelength range has been expanded by passing it through the hollow fiber 30. The pulse compression device 40 compensates for the dispersion of the introduced pulsed light in the optical path from the time the pulsed light is introduced until it is taken out.

[0034] As shown in Figure 2, the pulse compression device 40 comprises a plurality of chirp mirrors 41, a spectral prism 42, a plurality of cylindrical mirrors 43, a deformable mirror 44, and at least one shielding body 45.

[0035] In this example, the pulse compression device 40 is equipped with two pairs of chirp mirrors 41. However, the pulse compression device 40 may be equipped with one pair or three or more pairs of chirp mirrors 41.

[0036] Multiple chirp mirrors 41 reflect pulsed light in the optical path to compensate for the dispersion of the introduced pulsed light. In this example, each chirp mirror 41 has a dielectric multilayer film in which dielectrics with different refractive indices are stacked. Each chirp mirror 41 compensates for a portion of the dispersion of pulsed light by making the length of the optical path different according to the wavelength by making the layer that reflects the pulsed light different according to the wavelength. In this example, the dispersion compensation performed by the multiple chirp mirrors 41 may also be described as compression of pulsed light.

[0037] The spectral prism 42 receives pulsed light reflected by multiple chirp mirrors 41 via a periscope and a planar total reflection mirror (e.g., a silver (Ag) mirror). The spectral prism 42 spectrally separates (in other words, demultiplexes) the introduced pulsed light so that the optical paths differ according to wavelength. In this example, the spectral prism 42 is made of a glass called SF56. The spectral prism 42 may be made of a glass other than SF56. In this example, the spectral prism 42 corresponds to a spectral element. The pulse compression device 40 may be equipped with a spectral grating instead of the spectral prism 42.

[0038] In this example, the pulse compression device 40 has two cylindrical mirrors 43. However, the pulse compression device 40 may have one or more cylindrical mirrors 43. Multiple cylindrical mirrors 43 reflect the pulsed light dispersed by the spectral prism 42 so that the pulsed light is incident on the deformable mirror 44 along an incident direction perpendicular to the reference direction at different positions in the reference direction according to the wavelength.

[0039] The deformable mirror 44 has a reflective surface that receives pulsed light spectrally separated by the spectral prism 42, passing through multiple cylindrical mirrors 43, and also reflects the incident pulsed light. The deformable mirror 44 can deform its reflective surface so that the length of the optical path of the pulsed light changes depending on its position within the reflective surface.

[0040] In this example, the deformable mirror 44 has a thin film-like reflective surface and is configured to deform the reflective surface using multiple actuators, each having multiple different positions. For example, the actuators may be electrostatic actuators that deform by electrostatic force when a voltage is applied between two electrodes. Alternatively, the actuators may be piezoelectric actuators that use piezoelectric elements that deform when a voltage is applied. In this example, the deformable mirror 44 allows the position of the reflective surface in the incident direction to be changed at each of the multiple positions in the reference direction.

[0041] In this configuration, the deformable mirror 44 reflects the pulsed light in the optical path to compensate for the portion of the dispersion of the pulsed light introduced into the pulse compression device 40 that was not compensated by the multiple chirp mirrors 41. In this example, the dispersion compensation performed by the deformable mirror 44 may also be described as compression of the pulsed light.

[0042] The pulsed light reflected by the deformable mirror 44 is reflected by a plurality of cylindrical mirrors 43 and introduced into the spectral prism 42. The pulsed light introduced into the spectral prism 42 is combined (in other words, synthesized), and the combined pulsed light is derived from the pulse compressor 40 as pulsed light with a pulse width of 10 [fs] or less. In this example, the pulse width of the pulsed light derived from the pulse compressor 40 is approximately 6 [fs]. Note that the pulse compressor 40 does not necessarily have to be equipped with a plurality of chirp mirrors 41. In this case, the deformable mirror 44 may compensate for all of the dispersion of the pulsed light introduced into the pulse compressor 40.

[0043] The shielding body 45 shields (i.e., does not transmit) the pulsed light in the optical path corresponding to the suppression range which is a part of the wavelength range of the pulsed light. In this example, the shielding body 45 is located near the reflecting surface of the deformable mirror 44. By arranging it near the reflecting surface of the deformable mirror 44, components having wavelengths within any unwanted suppression range can be easily removed. In this example, the shielding body 45 corresponds to a wavelength component suppression means for suppressing components of the pulsed light having wavelengths within the suppression range.

[0044] Note that the wavelength component suppression means may include a reflector that reflects the pulsed light in the optical path corresponding to the suppression range instead of the shielding body 45, so that components of the pulsed light having wavelengths within the suppression range do not enter the deformable mirror 44. Further, the wavelength component suppression means may include a modulator such as a spatial phase modulator instead of the shielding body 45.

[0045] By the way, biological substances contain a relatively large amount of water. On the other hand, water absorbs light having wavelengths near 1450 [nm] and 1950 [nm] more greatly than light having other wavelengths. If the water contained in the biological substance absorbs light excessively greatly, there is a risk that the biological substance is damaged by being excessively heated.

[0046] In contrast, in this example, the suppression range consists of a first suppression range including 1450 [nm] and a second suppression range including 1950 [nm]. In this example, there are two shielding bodies 45 provided in the pulse compression device 40. In this example, one of the two shielding bodies 45 is located in the optical path corresponding to the first suppression range, and the other of the two shielding bodies 45 is located in the optical path corresponding to the second suppression range. With such a configuration, according to the pulse compression device 40, even when the object irradiated with the pulsed light is a living body, it is possible to suppress the living body from being excessively heated.

[0047] Note that the suppression range may be only one of the first suppression range and the second suppression range. In this case, the shielding body 45 provided in the pulse compression device 40 may be one. Note that the suppression range may include three or more ranges. In this case, the shielding body 45 provided in the pulse compression device 40 may be three or more.

[0048] (Operation) Next, the operation of the optical system 1 of the first embodiment will be described. First, the deformable mirror 44 of the pulse compression device 40 deforms the reflecting surface so that the optical path length changes according to the position within the reflecting surface that reflects the pulsed light spectrally split by the spectroscopic prism 42.

[0049] Next, the laser pulse light source 10 repeatedly generates pulsed light which is pulsed light. Next, the pulsed light generated by the laser pulse light source 10 is introduced into the optical parametric amplification device 20.

[0050] The optical parametric amplification device 20 uses the introduced pulsed light as signal light and generates idler light by amplifying it with pump light, and导出 the generated pulsed light which is the idler light.

[0051] Next, the pulsed light导出 by the optical parametric amplification device 20 is introduced into the hollow fiber 30. When the introduced pulsed light passes through the hollow fiber 30, self-phase modulation occurs in the pulsed light. As a result, the wavelength range of the pulsed light is expanded and dispersion occurs in the pulsed light.

[0052] Next, the pulsed light whose wavelength range has been expanded by passing through the hollow fiber 30 is introduced into the pulse compression device 40 via a periscope or the like. The plurality of chirp mirrors 41 of the pulse compression device 40 reflect the pulsed light so as to compensate for the dispersion of the introduced pulsed light in the optical path. As a result, a part of the dispersion of the pulsed light is compensated.

[0053] Next, the pulsed light reflected by the plurality of chirp mirrors 41 is introduced into the spectroscopic prism 42. The spectroscopic prism 42 splits the introduced pulsed light so as to make the optical path different according to the wavelength.

[0054] Next, the pulsed light spectrally separated by the spectral prism 42 is reflected by the multiple cylindrical mirrors 43 and incident on the deformable mirror 44. The deformable mirror 44 reflects the pulsed light in the optical path to compensate for the portion of the dispersion of the pulsed light introduced into the pulse compression device 40 that was not compensated for by the multiple chirp mirrors 41.

[0055] Next, the pulsed light reflected by the deformable mirror 44 is reflected by a plurality of cylindrical mirrors 43 and introduced into the spectral prism 42. The pulsed light introduced into the spectral prism 42 is combined, and the combined pulsed light is derived from the pulse compressor 40.

[0056] As described above, the pulse compression device 40 of the first embodiment compensates for the dispersion of the introduced pulsed light in the optical path from the time the pulsed light, whose wavelength range has been expanded by passing through the hollow fiber 30, is introduced until it is taken out. The pulse compression device 40 comprises a spectroscopic element (in this example, a spectroscopic prism 42) that spectrally separates the pulsed light so that the optical path differs according to the wavelength, and a deformable mirror 44 that has a reflective surface that reflects the spectrally separated pulsed light and can deform the reflective surface so that the length of the optical path changes depending on the position within the reflective surface.

[0057] This method allows for highly accurate compensation of the dispersion inherent in pulsed light. As a result, the pulse width can be made sufficiently short.

[0058] Furthermore, the pulse compression device 40 of the first embodiment includes wavelength component suppression means (in this example, a shielding body 45) that suppresses components of pulsed light having wavelengths within a predetermined suppression range.

[0059] Incidentally, components of pulsed light with wavelengths within a certain range may adversely affect the object being irradiated with the pulsed light. For example, if the object being irradiated with pulsed light is a living organism, components of the pulsed light with wavelengths that are easily absorbed by water may excessively heat the organism.

[0060] In contrast, the pulse compression device 40 suppresses the components of the pulsed light that have wavelengths within the suppression range. This makes it possible to suppress components of the pulsed light that adversely affect the object being irradiated with the pulsed light. As a result, adverse effects on the object being irradiated with the pulsed light can be suppressed.

[0061] Furthermore, in the pulse compression device 40 of the first embodiment, the wavelength component suppression means includes a shielding body 45 that shields pulsed light in the optical path corresponding to the suppression range.

[0062] According to this, pulsed light is shielded in the optical path corresponding to the suppression range. This makes it easy to suppress the component of the pulsed light that has a wavelength within the suppression range.

[0063] Furthermore, in the pulse compression device 40 of the first embodiment, the shielding body 45 is located near the reflective surface of the deformable mirror 44.

[0064] Incidentally, in the optical path, near the reflective surface of the deformable mirror 44 (for example, on the optical path of light incident from the cylindrical mirror 43 to the deformable mirror 44), the spectrally separated light is most spread out and easily separated by wavelength (in other words, the positions corresponding to wavelength are most widely distributed). Therefore, by positioning the shielding body 45 near the reflective surface of the deformable mirror 44, as in the pulse compression device 40, the suppression range can be controlled with high precision.

[0065] The shielding body 45 may be one or multiple units. Furthermore, the size of the shielding body 45 may be changed according to the width of the suppression range. The pulse compression device 40 may also use a mechanism to mechanically move the shielding body 45 to precisely set the suppression range.

[0066] Furthermore, in the pulse compression device 40 of the first embodiment, the suppression range includes at least one of a first suppression range including 1450 [nm] and a second suppression range including 1950 [nm]. In this example, the first suppression range is 1400 [nm] to 1500 [nm], and the second suppression range is 1900 [nm] to 2000 [nm].

[0067] As mentioned above, 1450 nm and 1950 nm are wavelengths that are easily absorbed by water. Therefore, by including at least one of a first suppression range including 1450 nm and a second suppression range including 1950 nm in the pulse compression device 40, it is possible to suppress excessive heating of living organisms even when the object irradiated with pulsed light is a living organism.

[0068] Thus, by equipping the pulse compression device 40 with wavelength component suppression means, it is possible to generate pulsed light with a narrow pulse width (for example, pulsed light with a pulse width of 10 [fs] or less) in which components with wavelengths within an arbitrary suppression range are suppressed. Therefore, the pulse compression device 40 can be applied to tools for high-speed in vivo diagnostics, such as optical CT scanners, or optical devices, such as optical processing devices, that use this pulsed light.

[0069] <Second Embodiment> Next, the optical system of the second embodiment will be described. The optical system of the second embodiment differs from the optical system of the first embodiment in that the suppression range is limited to only the second suppression range. The following will focus on the differences. In the description of the second embodiment, parts that are given the same reference numerals as those used in the first embodiment are the same or substantially the same.

[0070] The pulse compression device 40 of the second embodiment has one shielding body 45. The suppression range consists of a second suppression range including 1950 [nm]. The shielding body 45 is located in the optical path corresponding to the second suppression range.

[0071] The pulse compression device 40 of the second embodiment can also achieve the same operation and effects as the pulse compression device 40 of the first embodiment.

[0072] <Third Embodiment> Next, the optical system of the third embodiment will be described. The optical system of the third embodiment differs from the optical system of the first embodiment in that the suppression range is limited to only the first suppression range. The differences will be described below. In the description of the third embodiment, parts that are given the same reference numerals as those used in the first embodiment are the same or substantially the same.

[0073] The pulse compression device 40 of the third embodiment has one shielding body 45. The suppression range consists of a first suppression range including 1450 [nm]. The shielding body 45 is located in the optical path corresponding to the first suppression range.

[0074] The pulse compression device 40 of the third embodiment can also achieve the same operation and effects as the pulse compression device 40 of the first embodiment.

[0075] <Experimental Examples> Next, experimental examples using the optical system 1 of the first embodiment, second embodiment, third embodiment, and comparative example will be described. The optical system 1 of the comparative example is an optical system 1 in which the shielding body 45 is removed from the pulse compression device 40 of the first embodiment.

[0076] Figure 3 shows the spectrum of the change in intensity of pulsed light derived from the pulse compression device 40 with respect to wavelength. In Figure 3, in order to avoid overlapping curves, offset values ​​of 0.3, 0.2, and 0.1 are added to the normalized intensity in the comparative example, the second embodiment, and the third embodiment, respectively.

[0077] Figure 4 shows the intensity waveforms representing the change in pulse light intensity with respect to delay time, obtained by Fourier transforming the spectrum of Figure 3. In Figure 4, as in Figure 3, offset values ​​of 0.3, 0.2, and 0.1 are added to the intensity in the comparative example, the second embodiment, and the third embodiment, respectively, in order to avoid overlapping curves.

[0078] Figure 5 shows the spectrum of the change in fluorescence intensity (in other words, fluorescence intensity) with respect to wavelength when a fluorescent dye (in this example, ICG (Indocyanine Green)) encapsulated in a protein (in this example, gelatin) is excited by pulsed light emitted from the pulse compression device 40. In this example, ICG produces fluorescence upon two-photon excitation.

[0079] As shown in Figure 5, fluorescence can be induced in ICG by pulsed light derived from the pulse compression device 40 using any of the optical systems 1 of the first, second, and third embodiments. In other words, even when components of the pulsed light having wavelengths within a suppression range that include wavelengths easily absorbed by water are suppressed, as in the optical systems 1 of the first, second, and third embodiments, fluorescence can be induced in ICG by said pulsed light.

[0080] Therefore, according to the optical system 1 of the first, second, and third embodiments, even when the object to which pulsed light is irradiated is a living organism, fluorescence can be generated in the ICG by pulsed light derived from the pulse compression device 40 while suppressing excessive heating of the living organism.

[0081] It should be noted that the present invention is not limited to the embodiments described above. For example, various modifications can be made to the embodiments described above that are understandable to those skilled in the art, without departing from the spirit of the present invention.

[0082] 1 Optical System 10 Laser pulse light source 20 Optical parametric amplifier 30 Hollow fiber 40 Pulse compressor 41 Chirp mirror 42 Spectroscopic prism 43 Cylindrical mirror 44 Deformable mirror 45 Shielding

Claims

1. A pulse compression device for compensating for the dispersion of introduced pulsed light in an optical path from the time the introduced pulsed light, whose wavelength range has been extended by passing through a hollow fiber, is introduced until it is taken out, comprising: a spectroscopic element that spectrally separates the pulsed light so that the optical path differs according to the wavelength; and a deformable mirror having a reflective surface that reflects the spectrally separated pulsed light, the reflective surface being deformable so that the length of the optical path changes according to the position within the reflective surface.

2. A pulse compression device according to claim 1, comprising wavelength component suppression means for suppressing a component of the pulse light having a wavelength within a predetermined suppression range.

3. A pulse compression device according to claim 2, wherein the wavelength component suppression means includes a shielding body that shields the pulse light in the optical path corresponding to the suppression range.

4. A pulse compression device according to claim 3, wherein the shielding body is located near the reflective surface of the deformable mirror.

5. A pulse compression device according to claim 2, wherein the suppression range includes at least one of a first suppression range including 1450 nm and a second suppression range including 1950 nm.

6. An optical system comprising: a hollow fiber through which pulsed light is introduced and which expands the wavelength range of the introduced pulsed light by passing through the fiber; and a pulse compression device according to any one of claims 1 to 5.

7. An optical device that uses pulsed light generated using the optical system described in claim 6.

8. A pulse compression method for compensating for the dispersion of introduced pulsed light in an optical path from the time the introduced pulsed light, whose wavelength range has been extended by passing through a hollow fiber, is introduced until it is extracted, comprising: deforming the reflective surface such that the length of the optical path changes according to the position within the reflective surface that reflects the pulsed light; spectrally dispersing the pulsed light so that the optical path differs according to the wavelength; and injecting the spectrally dispersed pulsed light onto the reflective surface.

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