JP2015137980A - observation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an observation device which can acquire an image of a sample such as a cell with high spatial resolution in short time using a terahertz wave and whose configuration can be simplified and downsized.SOLUTION: An observation device comprises: a first illumination system that includes a sample holding unit 20 having a sample loading stage 21 made up of a non-linear optical crystal and irradiates a sample loading stage surface 21a of the sample loading stage 21 with a terahertz wave in an inner side of the sample holding unit 20 for total reflection; a second illumination system that irradiates a total reflection area of the terahertz wave of the sample loading stage surface 21a via the sample holding unit 20 by overlapping at least one part with pulse-like probe light having a shorter wave length than that of the terahertz wave; and a detection system that detects a polarization state of the probe light reflected on the sample loading stage surface 21a and emerging from the sample holding unit 20, and generates an image of a sample Sa loaded on the sample loading stage 21.

Description

  The present invention relates to an observation apparatus that observes a sample using terahertz waves.

  In recent years, spectroscopic measurement techniques using terahertz waves have been developed. Terahertz waves are sensitive not only to the evaluation of solid samples such as semiconductors and amino acid crystals, but also to the measurement of biological samples containing a large amount of aqueous solutions and water. Attention has been paid. However, terahertz waves are very strongly absorbed by water, and in the case of observation by transmission measurement, it takes time and effort to reduce the thickness of the sample. Further, since the wavelength of the terahertz wave is very long compared to visible light, the spatial resolution is poor.

  On the other hand, for example, a sensor device using a total reflection optical system that can use an evanescent wave is known (see, for example, Patent Document 1). If this sensor device is used, the depth of incidence of the terahertz wave on the sample can be reduced, so that even a sample containing a large amount of water can be easily observed with the terahertz wave. In addition, by allowing a terahertz wave to be incident on a sample using a minute aperture, it is possible to achieve a resolution exceeding the diffraction limit even in a direction parallel to the total reflection surface (sample mounting surface) of the terahertz wave. .

JP 2013-190311 A

  However, the sensor device disclosed in Patent Document 1 needs to spatially scan the sample with respect to the sensor device when imaging the sample with high spatial resolution exceeding the diffraction limit. For this reason, it takes time to acquire an image, and when the sample is an adhesive cell or the like, scanning may be difficult and may not be observed. Further, since a scanning mechanism is required, the configuration is complicated, and there is a concern that the apparatus will be enlarged.

  Accordingly, an object of the present invention made in view of such a viewpoint is to provide an observation apparatus that can acquire an image of a sample such as a cell with high spatial resolution in a short time using terahertz waves, and that can be easily and compactly made. is there.

An observation apparatus according to the present invention that achieves the above object is as follows.
A first irradiation system having a sample holding unit including a sample mounting table made of a non-linear optical crystal, and irradiating the sample mounting surface of the sample mounting table with a terahertz wave inside the sample holding unit;
A second irradiation system that irradiates a pulsed probe light having a wavelength shorter than that of the terahertz wave at least partially over the total reflection region of the terahertz wave on the sample mounting surface through the sample holding unit;
A detection system that detects a polarization state of the probe light reflected from the sample mounting surface and emitted from the sample holding unit to generate an image of the sample mounted on the sample mounting table;
Is provided.

The sample holder has an optical element bonded to a surface of the sample mounting table opposite to the sample mounting surface,
The first irradiation system irradiates the terahertz wave to the sample mounting surface from the optical element through the sample mounting table and totally reflects the same,
The second irradiation system irradiates the probe light onto the sample mounting surface through the optical element and the sample mounting table,
The detection system may detect a polarization state of the probe light emitted from the sample holder through the sample mounting table and the optical element.

The optical element is composed of a nonlinear optical crystal,
In the first irradiation system, it is preferable that pump light is incident on the optical element to generate the terahertz wave in the optical element, and the terahertz wave is totally reflected on the sample mounting surface.

  The first irradiation system may be configured such that pump light is incident on the sample mounting table, the terahertz wave is generated in the sample mounting table, and the terahertz wave is totally reflected on the sample mounting surface.

  The probe light and the pump light may be near infrared light.

  The first irradiation system may be configured such that a terahertz wave is incident on the optical element and the terahertz wave is totally reflected on the sample mounting surface.

  In the sample holder, the sample placement surface and the probe light incident surface may be parallel to each other.

  The terahertz wave and the probe light may be irradiated coaxially on the sample mounting surface.

  The detection system may generate an image of the sample based on a difference in polarization state of the probe light between a state where the sample is mounted on the sample mounting table and a state where the sample is not mounted.

  The sample mounting surface may have a reflective coat of the probe light.

  According to the present invention, it is possible to provide an observation apparatus that can acquire an image of a sample such as a cell with high spatial resolution in a short time using terahertz waves, and that can be easily and miniaturized.

It is a schematic structure figure of the whole observation apparatus concerning a 1st embodiment. FIG. 2 is a partial detail view of FIG. 1. It is a schematic block diagram of the whole observation apparatus which concerns on 2nd Embodiment. FIG. 4 is a partial detail view of FIG. 3. It is a partial detail drawing of the observation apparatus which concerns on 3rd Embodiment. It is a partial detail drawing of the observation apparatus which concerns on 4th Embodiment. It is a partial detailed view of an observation apparatus according to a fifth embodiment.

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

(First embodiment)
FIG. 1 is a schematic configuration diagram of the entire observation apparatus according to the first embodiment. This observation apparatus is for microscopic observation of a sample. In FIG. 1, a laser light source 11 emits a femtosecond near-infrared pulsed laser beam. For example, a titanium sapphire laser that oscillates a broadband near-infrared pulsed laser beam is used. The femtosecond near-infrared pulsed laser light emitted from the laser light source 11 is branched into pump light and probe light by the beam splitter 12. The pump light is incident on the pulse front tilt optical system 13. The pulse front tilt optical system 13 includes, for example, a diffraction grating, a lens, and the like, and emits the pulse front of the incident pump light while tilting it (see, for example, JP-A-2011-203339). The pump light emitted from the pulse front tilt optical system 13 is incident on the sample holder 20 that holds the sample Sa from its side surface.

  On the other hand, the probe light branched by the beam splitter 12 passes through the half-wave plate 31, the optical path adjustment optical system 32, the beam expander 33, the condenser lens 34, the reflection mirror 35, and the objective lens 36, and becomes a parallel light sample. The light enters the sample holder 20 from the lower surface of the holder 20 in an oblique direction with respect to the optical axis of the objective lens 36. The probe light reflected from the sample holder 20 and emitted from the lower surface of the sample holder 20 is polarized through the objective lens 36, the imaging lens 40, the quarter wavelength plate 41, and the half wavelength plate 42. The light enters the beam splitter 43 and is branched into an S-polarized component and a P-polarized component. The branched S-polarized component and P-polarized component are optically adjusted by the optical path adjusting optical systems 44 and 45 so that their optical path lengths are equal, and then emitted in parallel from the polarizing beam splitter 46 to be picked up by the image sensor 48 of the camera 47. Are formed in different light receiving areas, and the output of the image sensor 48 is processed by the signal processing circuit 49 to generate an image of the sample Sa by the terahertz wave.

  FIG. 2 is a partial detail view of the sample holder 20 and the objective lens 36 of FIG. The sample holding unit 20 includes a sample mounting table 21 having a sample mounting surface 21a on which the sample Sa is mounted, and an optical element 22 bonded to the surface of the sample mounting table 21 opposite to the sample mounting surface 21a. Have. The optical element 22 may be bonded to the sample mounting table 21 with an adhesive, for example, or may be bonded to the sample mounting table 21 in a detachable manner. A reflection coating 23 that reflects the probe light is formed on the sample mounting surface 21 a, and the sample Sa is mounted on the reflection coating 23. The sample mounting table 21 and the optical element 22 are each formed in a flat plate shape, and the sample mounting surface 21a and the incident surface 22a of the optical element 22 on which the probe light is incident (the lower surface of the sample holding unit 20) are parallel to each other. . Therefore, the entire sample holder 20 is flat.

The sample mounting table 21 and the optical element 22 are made of LiNbO ₃ crystal. The pump light emitted from the pulse front tilt optical system 13 in FIG. 1 is incident from the side surface 22b of the optical element 22 substantially perpendicularly to the side surface 22b. The optical element 22 propagates the incident pump light and generates a terahertz wave pulse by difference frequency mixing at an inclined pulse front condensing position (Cherenkov radiation phenomenon). The terahertz wave generated in a pulse shape in the optical element 22 is totally reflected by the sample mounting surface 21 a via the sample mounting table 21.

  On the other hand, the parallel probe light obliquely irradiated from the incident surface 22a of the optical element 22 to the sample holding unit 20 by the objective lens 36 is propagated almost coaxially with the terahertz wave through the optical element 22 and the sample mounting table 21. It is totally reflected by the reflective coating 23 on the sample mounting surface 21a. The probe light totally reflected by the reflection coat 23 is emitted from the lower surface of the sample holding unit 20 (incident surface 22a of the optical element 22) through the sample mounting table 21 and the optical element 22, and then passes through the objective lens 36 to form an imaging lens. 40 (see FIG. 1).

  Here, since the crystal axis of the optical element 22 efficiently generates terahertz waves, in FIG. 2, the optical axis direction of the objective lens 36 is Z, and the propagation direction of the pump light in the optical element 22 is Y, ZY. When the orthogonal direction is X, the direction is rotated by 90 ° around the Y axis. The polarization direction of the pump light is the Z direction of the crystal axis of the optical element 22. As a result, a high-intensity terahertz wave is radiated in the optical element 22, and the radiation angle (Cherenkov angle) θ is about 60 ° with respect to the propagation direction of the pump light. In this case, the incident angle of the terahertz wave to the sample placement surface 21a is about 30 °, but the refractive index n of the sample Sa placed on the sample placement surface 21a is, for example, n = 2.1. Since the critical angle of total reflection is about 24 ° (calculated assuming that the refractive index of the sample mounting table 21 is 5.11), the generated terahertz wave can be totally reflected by the sample mounting surface 21a.

  On the other hand, the crystal axis of the sample mounting table 21 is rotated about 45 ° in the XY plane of the probe light with respect to the crystal axis of the optical element 22 in order to detect the terahertz wave component modulated by the sample Sa. . As a result, while the probe light propagates through the sample mounting table 21, the polarization changes due to the birefringence (electro-optic effect) of the sample mounting table 21 induced by the terahertz wave electric field, but the optical element 22 is affected by the terahertz wave electric field. The refractive index change is very small and can be hardly affected. That is, it can be considered that the polarization change of the probe light due to the terahertz wave occurs only in the sample mounting table 21.

  In the present embodiment, the first irradiation system includes the laser light source 11, the pulse front tilt optical system 13, and the sample holder 20. The second irradiation system includes the laser light source 11, the half-wave plate 31, the optical path adjustment optical system 32, the beam expander 33, the condensing lens 34, the reflection mirror 35, the objective lens 36, and the sample holder 20. ing. The detection system includes an objective lens 36, an imaging lens 40, a quarter-wave plate 41, a half-wave plate 42, a polarizing beam splitter 43, optical path adjusting optical systems 44 and 45, a polarizing beam splitter 46, a camera 47, and signal processing. A circuit 49 is included.

  In the first irradiation system, when the terahertz wave generated in the optical element 22 by the incidence of the pump light on the optical element 22 of the sample holding unit 20 is totally reflected by the sample mounting surface 21a, the sample mounting surface Since the evanescent component exuded from 21a interacts with the sample to cause attenuation and phase delay, the terahertz wave component after total reflection includes information on the sample Sa. Therefore, by detecting the polarization change of the probe light emitted from the optical crystal 22, an image of the sample Sa can be generated based on the terahertz wave component modulated by the sample Sa. Here, since the polarization change of the probe light due to the terahertz wave occurs only on the sample mounting table 21, when the sample mounting table is thin, the terahertz wave can be detected near the sample (near-field region), and the spatial resolution is diffracted. It can be raised above the limit. The polarization direction of the probe light applied to the sample mounting surface 21a is adjusted in advance by the half-wave plate 31 so that the polarization state is largely changed by the birefringence generated by the sample mounting table 21.

  Here, the quarter-wave plate 41 and the half-wave plate 42 constituting the detection system are incident on the polarization beam splitter 43 via the sample holder 20 in a state where no terahertz wave is incident on the sample mounting table 21. It is preferable that the polarization of the probe light to be adjusted to be linearly polarized at 45 degrees. By adjusting in this way, the intensity ratio between the S-polarized light and the P-polarized light of the probe light polarized and separated by the polarizing beam splitter 43 becomes 1: 1 when the terahertz wave is not incident on the sample mounting table 21, and the camera 47. An image of the probe light of the S-polarized component and the P-polarized component having the same intensity is formed in. On the other hand, in the state where the terahertz wave is incident on the sample mounting table 21 and birefringence occurs in the sample mounting table 21, the polarization of the probe light changes due to birefringence and becomes elliptically polarized light. As a result, the polarization beam splitter 43 The intensity ratio between the separated S-polarized component and P-polarized component changes, and the intensity ratio of the image formed on the image sensor 48 also changes accordingly.

  Accordingly, if the signal processing circuit 49 calculates the difference between the image of the S-polarized component and the image of the P-polarized component acquired by the image sensor 48, the SHz is not incident on the sample mounting table 21 in the state where the terahertz wave is not incident on the sample mounting table 21. Since the signal intensity of the polarized light and that of the P-polarized light are equal, the signal intensity difference is zero. On the other hand, when the terahertz wave is incident on the sample mounting table 21, the signal intensity difference between the S-polarized light and the P-polarized light is not zero. That is, the electric field amplitude intensity of the terahertz wave is obtained.

  In this way, if the images of the S-polarized component and the P-polarized component of the probe light propagated through the sample mounting table 21 are formed on the image sensor 48, that is, the image sensor 48 is optically conjugate with the inside of the sample mounting table 21. If it arrange | positions so that it may become a favorable relationship, the spatial distribution of the electric field amplitude of the terahertz wave which injected into the sample mounting base 21 is acquirable. Moreover, since the terahertz wave incident on the sample mounting table 21 is modulated by the sample Sa and the information of the sample Sa is transferred, the sample Sa is microscopically observed by acquiring the spatial distribution of the electric field amplitude of the terahertz wave. It becomes possible to do. Further, as necessary, the relative time difference between the probe light and the terahertz wave is changed by the optical path adjusting optical system 32 in the optical path of the probe light. Thereby, the time of the terahertz wave to be detected can be swept, and the time change of the terahertz wave can be detected as a sequence of images in the signal processing circuit 49. In addition, the signal processing circuit 49 can generate a frequency spectrum image by performing a Fourier transform on the detected sequence of images as necessary.

  The image of the sample Sa is generated by generating an image of the sample Sa based on the difference between the polarization state of the probe light between the state where the sample Sa is placed on the sample placement table 21 and the state where it is not placed. Also good. That is, the image information obtained when the sample mounting table 21 is irradiated with the terahertz wave and the probe light in a state where the sample Sa is not mounted on the sample mounting table 21, and the sample Sa is mounted on the sample mounting table 21. In this state, image information obtained when the sample mounting table 21 is irradiated with the terahertz wave and the probe light may be acquired, and an image of the sample Sa may be generated from the difference between the image information of the two. In this way, a highly accurate image of the sample Sa from which the background image has been subtracted can be obtained.

  According to the observation apparatus according to the present embodiment, a microscope image having a high spatial resolution of the sample Sa such as a cell can be acquired in a short time without spatially scanning the sample Sa for imaging with a reflection microscope. Can do. In addition, since the high-intensity terahertz wave radiated in the oblique direction from the propagation direction of the pump light by the Cherenkov radiation phenomenon in the optical element 22 is irradiated to the sample placement surface 21a as it is and totally reflected. Can be simplified. Furthermore, since the sample light is not irradiated with the pump light, the sample Sa is not affected by the pump light. Therefore, a highly accurate image of the sample Sa using terahertz waves can be obtained.

Further, the terahertz wave generating optical element 22 and the terahertz wave detecting sample mounting table 21 constituting the sample holding unit 20 can be configured by, for example, a single nonlinear optical element having different crystal axes, so that high-intensity terahertz Both wave generation and near-field imaging can be easily realized. Further, by making the sample holder 20 flat, it can be easily inserted into a small space (working distance) between the objective lens 36 and the sample Sa. For example, a beam splitter is arranged between the objective lens and the sample. Compared with the case where the terahertz wave and the probe light are multiplexed or demultiplexed, the aberration of the microscopic observation is not greatly affected. In addition, if the sample holder 20 is configured so that the sample mounting table 21 is detachable with respect to the optical element 22, the performance of the apparatus can be kept stable, thereby simplifying performance management and reducing costs. In addition, as a material of the sample mounting table 21 and the optical element 22, other types of crystal materials such as LiTaO ₃ may be used. In addition, while taking into consideration the refraction between the sample mounting table 21 and the optical element 22 and the total reflection critical angle on the sample mounting surface 21 a, different types of crystals having different refractive indexes are applied to the sample mounting table 21 and the optical element 22. Each may be arranged. In FIG. 1, the reflection mirror 35 is used when the probe light is incident on the objective lens, but it may be separated from the component emitted from the element 20 using a non-polarizing beam splitter.

(Second Embodiment)
FIG. 3 is a schematic configuration diagram of an entire observation apparatus according to the second embodiment. The observation apparatus according to the present embodiment includes a terahertz wave generating optical system 50 that generates a terahertz wave pulse by entering the pump light branched by the beam splitter 12 as a first irradiation system. The terahertz wave generating optical system 50 includes a pump light adjusting optical system 51, a terahertz wave generating element 52, and a terahertz wave condensing optical system 53. The pump light from the beam splitter 12 is incident on the terahertz wave generating element 52 through the pump light adjusting optical system 51. Thereby, a terahertz wave pulse is emitted from the terahertz wave generating element 52.

Here, the terahertz wave generating element 52 can use a nonlinear optical crystal, a photoconductive antenna, or the like. The pump light adjusting optical system 51 is appropriately configured according to the terahertz wave generating element 52 used. For example, when the terahertz wave generating element 52 is configured by a photoconductive antenna, the pump light adjusting optical system 51 is configured by using a lens as shown in FIG. Further, when the terahertz wave generating element 52 is composed of LiNbO ₃ , LiTaO ₃ or the like that is a nonlinear optical crystal that generates a high-intensity terahertz wave, the pump light adjusting optical system 51 has an optical element such as a diffraction grating in FIG. It may be configured by a pulse front tilt optical system as shown.

  The terahertz wave generated by the terahertz wave generating element 52 enters the sample holding unit 20 that holds the sample Sa via the terahertz wave condensing optical system 53 from the side surface. The terahertz wave condensing optical system 53 includes a plastic lens or a parabolic mirror that transmits the terahertz wave.

  On the other hand, in the second irradiation system, the probe light adjusted to a predetermined light beam diameter by the beam expander 33 passes through the non-polarizing beam splitter 60, the imaging lens 61, and the objective lens 36, and is converted into parallel light to the sample holder 20. It is comprised so that it may inject into the sample holding part 20 perpendicularly | vertically along the optical axis direction of the objective lens 36 from the lower surface of this. In the detection system, the probe light reflected from the sample holding unit 20 and emitted from the lower surface of the sample holding unit 20 passes through the objective lens 36, the imaging lens 61, and the non-polarizing beam splitter 60. 41.

Further, as shown in the partial detail view in FIG. 4, the sample holding unit 20 includes a plate-like sample mounting table 21 made of a nonlinear optical crystal such as LiNbO ₃ or LiTaO ₃ and the like, as in the case of the first embodiment. It has an optical element 22 and a probe light reflecting coat 23 formed on the sample mounting surface 21 a of the sample mounting table 21. In the present embodiment, the optical element 22 acts as a prism that refracts the terahertz wave incident from the side surface 22b and totally reflects the sample mounting surface 21a through the sample mounting table 21. Therefore, the side surface 22b of the optical element 22 on which the terahertz wave is incident is formed to be inclined with respect to the central ray of the terahertz wave.

  Since the other configuration is the same as that of the first embodiment, the same components as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the present embodiment, when the terahertz wave incident on the sample holder 20 is irradiated onto the sample mounting surface 21a and totally reflected, the evanescent light oozes out on the sample Sa as in the case of the first embodiment. Interact with the sample Sa. As a result, the terahertz wave is modulated by the sample Sa, birefringence occurs in the sample mounting table 21, and the polarization of the probe light changes. Therefore, as described in the first embodiment, if a change in the polarization of the probe light is detected, an image of the sample Sa can be generated based on the terahertz wave component modulated by the sample Sa.

  According to the present embodiment, since the terahertz wave and the probe light do not act on the sample placement surface 21a coaxially, the detection efficiency of the terahertz wave component is reduced as compared with the case of the first embodiment. A large-diameter terahertz wave can be generated by the wave generation optical system 50. Then, the terahertz wave generated by the terahertz wave generating optical system 50 can be condensed and incident on the optical element 22 as a high-intensity terahertz wave and totally reflected by the sample mounting surface 21a. It is possible to realize an improvement in signal strength that only compensates for the decrease. Note that the decrease in the detection light rate can be reduced by reducing the thickness of the sample mounting table 21. Further, since the probe light is irradiated from the optical axis direction (vertical irradiation) by the objective lens 36, the arrangement of the optical elements constituting the second irradiation system and the detection system is facilitated, and the configuration can be simplified. .

(Third embodiment)
FIG. 5 is a partial detail view of the observation apparatus according to the third embodiment. The observation apparatus according to the present embodiment is such that in the second embodiment, the terahertz wave and the probe light act on the sample placement surface 21a coaxially. Therefore, the second irradiation system is configured so that the probe light is obliquely irradiated by the objective lens 36 and incident on the incident surface 22a of the optical element 22 as in the first embodiment, and the detection system is also the first. The configuration is the same as in the first embodiment. Further, in the optical element 22 of the sample holding unit 20 constituting the first irradiation system, after the terahertz wave incident from the side surface 22b is refracted by the side surface 22b, it is totally reflected by the incident surface 22a and coaxial with the probe light. It is formed so as to irradiate the sample mounting surface 21a. Other configurations are the same as those of the second embodiment.

  According to the present embodiment, as in the second embodiment, a high-intensity terahertz wave generated from the terahertz wave generation optical system 50 (see FIG. 3) can be used, and the first embodiment Similarly, since the terahertz wave and the probe light are made to act on the sample placement surface 21a coaxially, the signal intensity and the detection light rate can be improved.

(Fourth embodiment)
FIG. 6 is a partial detail view of the observation apparatus according to the fourth embodiment. In the observation apparatus according to the present embodiment, in the third embodiment, the sample holder 20 includes a sample mounting table 21 and a probe light reflecting coat 23 formed on the sample mounting surface 21 a of the sample mounting table 21. It consists of and. That is, the sample holder 20 omits the optical element 22 shown in the first to third embodiments. The probe light is obliquely irradiated onto the lower surface (incident surface) 21 b of the sample mounting table 21 by the objective lens 36. A high-intensity terahertz wave generated from the terahertz wave generating optical system 50 (see FIG. 3) is incident from the side surface 21 c of the sample mounting table 21. The side surface 21c is formed so that the incident terahertz wave is refracted by the side surface 21c and then totally reflected by the lower surface 21b so as to irradiate the sample mounting surface 21a coaxially with the probe light. Other configurations are the same as those of the third embodiment.

  According to the present embodiment, since the terahertz wave is incident from the side surface 21c of the sample mounting table 21, the thickness of the sample mounting table 21 can be increased compared with the first to third embodiments, but the near field of the sample Sa. Since terahertz waves can be detected in a region, high spatial resolution can be realized, and the sample holder 20 can be formed using a single nonlinear optical element, so that there is an advantage that the configuration can be simplified and the cost can be reduced.

(Fifth embodiment)
FIG. 7 is a partial detail view of the observation apparatus according to the fifth embodiment. In the observation apparatus according to the present embodiment, in the first embodiment, the sample holding unit 20 includes a sample mounting table 21 and a probe light reflecting coat 23 formed on the sample mounting surface 21 a of the sample mounting table 21. The pump light is incident from the side surface 21c of the sample mounting table 21. In the present embodiment, the sample mounting table 21 propagates the incident pump light and generates a terahertz wave by difference frequency mixing at a converging position of an inclined pulse front, and a terahertz wave component by the probe light. And a function to detect. Therefore, the crystal axis of the sample mounting table 21 is appropriately set in consideration of the efficiency of both the above functions. The terahertz wave generated in the sample mounting table 21 is totally reflected by the sample mounting surface 21a. The probe light is obliquely irradiated onto the lower surface 21b of the sample mounting table 21 by the objective lens 36, and is irradiated on the sample mounting surface 21a coaxially with the terahertz wave. Other configurations are the same as those of the first embodiment.

  According to the present embodiment, similar to the fourth embodiment, since the sample holding unit 20 can be formed using one nonlinear optical element, there is an advantage that it can be configured more simply and cost can be reduced.

  In addition, this invention is not limited to the said embodiment, Many deformation | transformation or a change is possible. For example, in the second and third embodiments, the optical element 22 constituting the sample holding unit 20 is not limited to the same material as the sample mounting table 21, and has a refractive index close to that of the sample mounting table 21 and terahertz. It can be formed of any material that can transmit waves and probe light. In each of the above embodiments, the reflective coat 23 of the sample holder 20 may be omitted, and the incident surface 22a of the optical crystal 22 and the fourth and fifth embodiments of the first to third embodiments. An antireflection film for probe light may be formed on the lower surface 21 b of the sample mounting table 21. Furthermore, in the first embodiment and the third to fifth embodiments, the probe light does not necessarily have to be irradiated coaxially with the terahertz wave as long as the probe light partially overlaps the irradiation region of the terahertz wave with respect to the sample Sa.

  Further, the first irradiation system, the second irradiation system, and the detection system are not limited to the configuration described above. For example, the first irradiation system may be configured to irradiate the sample mounting surface 21 a of the sample mounting table 21 and totally reflect the terahertz wave inside the sample holding unit 20. The second irradiation system may be configured to irradiate the probe light at least partially overlapping the terahertz wave total reflection region of the sample placement surface 21a through the sample holding unit 20. The detection system may be configured to generate an image of the sample Sa by detecting the polarization state of the probe light reflected from the sample placement surface 21a and emitted from the sample holding unit 20.

  In the embodiment described above, the terahertz wave pulse is generated using the femtosecond near-infrared pulsed laser beam, but it corresponds to the difference frequency using the continuous wave laser beam having two different oscillation frequencies. A monochromatic terahertz wave may be generated. As a laser light source in this case, an Nd: YAG laser-excited KTP-OPO (Optical-Parametric-Oscillator) light source that outputs light of two wavelengths, or two tunable laser diodes can be used.

DESCRIPTION OF SYMBOLS 11 Laser light source 12 Beam splitter 13 Pulse front inclination optical system 20 Sample holding part 21 Sample mounting base 21a Sample mounting surface 21b Lower surface (incident surface)
DESCRIPTION OF SYMBOLS 22 Optical element 22a Incident surface 22b Side surface 23 Reflection coat 31 1/2 wavelength plate 32 Optical path adjustment optical system 33 Beam expander 34 Condensing lens 35 Reflection mirror 36 Objective lens 40 Imaging lens 41 1/4 wavelength plate 42 1/2 Wave plates 43, 46 Polarizing beam splitters 44, 45 Optical path adjusting optical system 47 Camera 48 Imaging device 49 Signal processing circuit 50 Terahertz wave generating optical system 51 Pump light adjusting optical system 52 Terahertz wave generating element 53 Terahertz wave condensing optical system 60 None Polarizing beam splitter 61 Imaging lens

Claims (10)

A first irradiation system having a sample holding unit including a sample mounting table made of a non-linear optical crystal, and irradiating the sample mounting surface of the sample mounting table with a terahertz wave inside the sample holding unit;
A second irradiation system that irradiates a pulsed probe light having a wavelength shorter than that of the terahertz wave at least partially over the total reflection region of the terahertz wave on the sample mounting surface through the sample holding unit;
A detection system that detects a polarization state of the probe light reflected from the sample mounting surface and emitted from the sample holding unit to generate an image of the sample mounted on the sample mounting table;
An observation apparatus comprising: The sample holder has an optical element bonded to a surface of the sample mounting table opposite to the sample mounting surface,
The first irradiation system irradiates the terahertz wave to the sample mounting surface from the optical element through the sample mounting table and totally reflects the same,
The second irradiation system irradiates the probe light onto the sample mounting surface through the optical element and the sample mounting table,
The detection system detects a polarization state of the probe light emitted from the sample holder through the sample mounting table and the optical element;
The observation apparatus according to claim 1. The optical element is composed of a nonlinear optical crystal,
The first irradiation system causes pump light to enter the optical element to generate the terahertz wave in the optical element, and the terahertz wave is totally reflected on the sample mounting surface.
The observation apparatus according to claim 2. The first irradiation system causes pump light to be incident on the sample mounting table to generate the terahertz wave in the sample mounting table, and totally reflects the terahertz wave on the sample mounting surface.
The observation apparatus according to claim 1. The probe light and the pump light are near infrared light,
The observation apparatus according to claim 3 or 4. The first irradiation system makes a terahertz wave incident on the optical element and totally reflects the terahertz wave on the sample mounting surface.
The observation apparatus according to claim 2. In the sample holder, the sample mounting surface and the incident surface of the probe light are parallel.
The observation apparatus according to any one of claims 1 to 6. The terahertz wave and the probe light are irradiated coaxially on the sample mounting surface,
The observation apparatus according to any one of claims 1 to 7. The detection system generates an image of the sample based on a difference in polarization state of the probe light between a state where the sample is placed on the sample placement table and a state where the sample is not placed.
The observation apparatus according to any one of claims 1 to 8. The sample mounting surface has a reflective coat of the probe light,
The observation apparatus according to any one of claims 1 to 9.

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