JP2008224452A - Device for measuring totally reflected terahertz wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for measuring totally reflected terahertz wave capable of readily measuring a measuring target with high sensitivity, even if the measuring target is a fluid material. <P>SOLUTION: The device 1 for measuring the terahertz wave is constituted so as to use a terahertz wave to acquire the data of the measuring target S by a total reflection measuring method and equipped with a light source 11, branch part 12, chopper 13, light path length difference adjusting part 14, polarizer 15, wave combining part 16, terahertz wave generation element 20, internal multiple total reflection prism 31, terahertz wave detection element 40, 1/4 wavelength plate 51, polarizing separation element 52, photodetectors 53A and 53B, differential amplifier 54 and lock-in amplifier 55. The internal multiple total reflection prism 31 inputs the terahertz wave outputted from the terahertz wave generation element 30 to the incident surface 31a, not only to propagate the input terahertz wave internally but also to totally reflect the same by four reflecting surfaces 31c-31f, to output the terahertz wave to the wave combining part 16 from the emitting surface 31b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a total reflection terahertz wave measuring apparatus.

  The terahertz wave is an electromagnetic wave having a frequency of about 0.01 THz to 100 THz corresponding to an intermediate region between the light wave and the radio wave, and has an intermediate property between the light wave and the radio wave. As an application of such a terahertz wave, a technique for acquiring information on the measurement object by measuring a time waveform of the electric field amplitude of the terahertz wave transmitted or reflected by the measurement object has been studied (see Patent Document 1). reference).

  A technique for measuring information on a measurement object using a terahertz wave is generally as follows. That is, the pulsed light output from the light source (for example, femtosecond laser light source) is bifurcated by the branching unit into pump light and probe light. Among them, the pump light is input to a terahertz wave generating element (for example, a nonlinear optical crystal or a photoconductive antenna element), and thereby a pulsed terahertz wave is generated from the terahertz wave generating element. The generated terahertz wave is transmitted or reflected by the measurement target unit to acquire information (for example, absorption coefficient, refractive index) of the measurement target, and then the terahertz wave detection element at substantially the same timing as the probe light. (E.g., an electro-optic crystal or a photoconductive antenna element).

  In the terahertz wave detecting element to which the terahertz wave and the probe light are input, the correlation between both lights is detected. For example, when an electro-optic crystal is used as a terahertz wave detecting element, the terahertz wave and the probe light are combined by a multiplexing unit and incident on the electro-optic crystal, and birefringence occurs along with the propagation of the terahertz wave in the electro-optic crystal. Is induced, and the polarization state of the probe light changes due to the birefringence. A change in the polarization state of the probe light in the electro-optic crystal is detected, and consequently, the electric field amplitude of the terahertz wave is detected, and information on the measurement object is obtained.

When acquiring information on a measurement object using a terahertz wave, not only the transmission or reflection of the terahertz wave at the measurement target unit but also the terahertz wave is totally reflected on one plane of the prism as disclosed in Patent Document 1. In some cases, the information on the measurement object is acquired by the terahertz wave by generating the evanescent component and irradiating the measurement object on the plane with the evanescent component of the terahertz wave. According to the description in Patent Document 1, the technique using the total reflection of terahertz waves has an effect that the measurement object is not limited to a solid.
JP 2004-354246 A

  Although the technique disclosed in Patent Document 1 can measure not only a solid but also a fluid such as a liquid as a measurement object, the measurement object is arranged on one plane of a prism that totally reflects a terahertz wave. There is a need. However, when the measurement object is a fluid, it is difficult to perform stable measurement by arranging the fluid measurement object on one plane of the prism. Further, since the object to be measured is only irradiated with the evanescent component of the terahertz wave by only one total reflection, the measurement sensitivity is low.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a total reflection terahertz wave measuring apparatus that can easily and highly sensitively measure a measurement object even if it is a fluid. And

  The total reflection terahertz wave measuring apparatus according to the present invention includes (1) a light source that outputs light, and (2) two branches of light output from the light source, and one of the two branched lights is used as pump light and the other (3) a terahertz wave generating element that generates and outputs a terahertz wave by inputting pump light output from the branching part, and (4) a terahertz wave generating element that outputs the terahertz wave. An internal multiple total reflection prism that inputs a terahertz wave to the incident surface, propagates the input terahertz wave internally and totally reflects it by a plurality of reflecting surfaces, and outputs the terahertz wave from the emitting surface to the outside. ) A terahertz wave detection element that inputs the terahertz wave output from the exit surface of the internal multiple total reflection prism and the probe light output from the branching section and detects the correlation between the terahertz wave and the probe light. Characterized in that it comprises a and. Furthermore, the total reflection terahertz wave measuring apparatus according to the present invention superimposes information on the measurement object arranged on each of the plurality of reflection surfaces of the internal multiple total reflection prism, and the total reflection terahertz wave measurement apparatus generates the terahertz wave when it is totally reflected. It is characterized by being efficiently acquired by the evanescent component of the terahertz wave.

  In this total reflection terahertz wave measuring apparatus, the light output from the light source is bifurcated by the branching unit and output as pump light and probe light. The pump light output from the branching unit is input to the terahertz wave generating element, and a terahertz wave is generated and output by the terahertz wave generating element. The terahertz wave output from the terahertz wave generating element is input to the incident surface of the internal multiple total reflection prism, propagates inside the internal multiple total reflection prism, and is totally reflected by a plurality of reflection surfaces, thereby internally multiple total reflection prism. Is output to the outside from the exit surface. The terahertz wave output from the exit surface of the internal multiple total reflection prism and the probe light output from the branch part are input to the terahertz wave detection element, and the terahertz wave detection element causes the terahertz wave to be detected between the terahertz wave and the probe light. Correlation is detected. At this time, the information about the measurement object arranged on each of the plurality of reflection surfaces of the internal multiple total reflection prism is efficiently acquired by the evanescent component of the terahertz wave generated at the time of total reflection of the terahertz wave.

  The total reflection terahertz wave measuring apparatus according to the present invention includes an optical path of pump light and a terahertz wave from the branching section to the terahertz wave detecting element, and an optical path of the probe light from the branching section to the terahertz wave detecting element. It is preferable to further include an optical path length difference adjusting unit for adjusting the difference. In this case, the optical path length difference adjustment unit adjusts the timing at which each of the terahertz wave and the probe light is input to the terahertz wave detection element, and the timing is swept so that the electric field amplitude of the pulse terahertz wave is adjusted. A time waveform is obtained. The optical path length difference adjusting unit may be provided in any optical system of pump light, probe light, and terahertz wave.

  In the total reflection terahertz wave measuring apparatus according to the present invention, it is preferable that the terahertz wave generating element is integrally provided on the incident surface of the internal multiple total reflection prism. It is preferable to further include an optical fiber for pump light that guides pump light to the provided terahertz wave generating element. It is preferable that an optical element having a collimating action with respect to the terahertz wave propagating through the internal multiple total reflection prism is formed on the incident surface side of the internal multiple total reflection prism. In the total reflection terahertz wave measuring apparatus according to the present invention, it is preferable that the terahertz wave detecting element is integrally provided on the output surface of the internal multiple total reflection prism, and the output surface of the internal multiple total reflection prism is provided. It is preferable to further include an optical fiber for probe light that guides the probe light to the provided terahertz wave detecting element. In addition, it is preferable that an optical element having a condensing function with respect to the terahertz wave propagating through the internal multiple total reflection prism is preferably formed on the exit surface side of the internal multiple total reflection prism.

  As described above, since the terahertz wave generating element or the terahertz wave detecting element is integrally provided on the internal multiple total reflection prism, these can be handled easily and can be miniaturized. Further, since the terahertz wave generating element or the terahertz wave detecting element provided integrally with the internal multiple total reflection prism is further provided with an optical fiber for guiding the pump light or the probe light, the handling thereof is further facilitated. . Further, if an optical element (for example, a lens or an off-axis parabolic mirror) having a collimating function or a condensing function is formed on the internal multiple total reflection prism, the terahertz wave generating element or the terahertz wave detecting element is a photoconductive antenna element. Is advantageous.

  It is preferable that the chief ray of the terahertz wave input to the incident surface of the internal multiple total reflection prism and the chief ray of the terahertz wave output from the exit surface of the internal multiple total reflection prism are on a common straight line. . In this case, the total reflection measurement method and the transmission measurement method can be switched by selecting and arranging either the internal multiple total reflection prism or the measurement object at the position of the internal multiple total reflection prism.

  The total reflection terahertz wave measuring apparatus according to the present invention preferably further includes moving means for moving one of the fluid as the measurement object and the internal multiple total reflection prism relative to the other. In this case, the measurement can be performed efficiently.

  The total reflection terahertz wave measuring apparatus according to the present invention can measure easily and with high sensitivity even if the measurement object is a fluid.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted. The configurations of the first comparative example and the second comparative example to be compared with the configuration of the embodiment of the present invention will be described first, and then the configuration of the embodiment will be described while comparing with the configuration of these comparative examples.

(First comparative example)
First, the terahertz wave measuring apparatus 8 according to the first comparative example will be described. FIG. 1 is a configuration diagram of a terahertz wave measuring apparatus 8 according to a first comparative example. The terahertz wave measuring device 8 shown in this figure acquires information on the measuring object S by transmission measurement using terahertz waves, and includes a light source 11, a branching unit 12, a chopper 13, and an optical path length difference adjusting unit. 14, the polarizer 15, the multiplexing unit 16, the terahertz wave generating element 20, the terahertz wave detecting element 40, the quarter wavelength plate 51, the polarization separating element 52, the photodetector 53A, the photodetector 53B, the differential amplifier 54, and A lock-in amplifier 55 is provided.

  The light source 11 is a femtosecond pulse laser light source that outputs pulsed light with a constant repetition period and preferably outputs pulsed laser light having a pulse width of about femtoseconds. The branching unit 12 is, for example, a beam splitter, splits the pulsed light output from the light source 11 into two, outputs one of the two branched pulsed light to the mirror M1 as pump light, and the other as the probe light to mirror. Output to M4.

  The chopper 13 is provided on the optical path of the pump light between the branching section 12 and the mirror M1, and alternately repeats the passage and blocking of the pump light at a constant cycle. The pump light output from the branching unit 12 and passing through the chopper 13 is sequentially reflected by the mirrors M <b> 1 to M <b> 3 and input to the terahertz wave generating element 20. The optical system of pump light from the branching section 12 to the terahertz wave generating element 20 is hereinafter referred to as “pump optical system”.

  The terahertz wave generating element 20 generates and outputs a pulsed terahertz wave by inputting pump light. For example, a nonlinear optical crystal (for example, ZnTe), a photoconductive antenna element (for example, an optical switch using GaAs), It is configured to include either a semiconductor (for example, InAs) or a superconductor. When the terahertz wave generating element 20 includes a non-linear optical crystal, the terahertz wave generating element 20 can generate a terahertz wave by a non-linear optical phenomenon that occurs as pump light enters.

  The terahertz wave is an electromagnetic wave having a frequency of about 0.01 THz to 100 THz corresponding to an intermediate region between the light wave and the radio wave, and has an intermediate property between the light wave and the radio wave. Further, the pulse terahertz wave is generated at a constant repetition period, and the pulse width is about several picoseconds. The terahertz wave output from the terahertz wave generation element 20 acquires information (for example, an absorption coefficient and a refractive index) of the measurement object S by passing through the measurement object S, and then is input to the multiplexing unit 16. The The terahertz wave optical system from the terahertz wave generating element 20 to the multiplexing unit 16 is hereinafter referred to as a “terahertz wave optical system”.

  On the other hand, the probe light output from the branching unit 12 is sequentially reflected by the mirrors M4 to M8, passes through the polarizer 15, and is input to the multiplexing unit 16. The optical system of the probe light from the branching unit 12 to the multiplexing unit 16 is hereinafter referred to as “probe optical system”. The four mirrors M4 to M7 constitute an optical path length difference adjusting unit 14. That is, when the mirrors M5 and M6 move, the optical path length between the mirrors M4 and M7 and the mirrors M5 and M6 is adjusted, and the optical path length of the probe optical system is adjusted. As a result, the optical path length difference adjusting unit 14 includes the optical path of the pump optical system and the terahertz wave optical system from the branching unit 12 to the multiplexing unit 16 and the probe from the branching unit 12 to the multiplexing unit 16. The difference from the optical path of the optical system can be adjusted.

  The multiplexing unit 16 inputs the terahertz wave output from the terahertz wave generation element 20 and transmitted through the measurement object S, and the probe light output from the branching unit 12 and arrived, and the terahertz wave and the probe light are coaxial with each other. Are combined and output to the terahertz wave detecting element 40. The combining unit 16 is preferably a pellicle that is a film-like mirror that is bonded to a rigid support frame and stretched thinly.

  The terahertz wave detection element 40 detects a correlation between the terahertz wave and the probe light. When the terahertz wave detecting element 40 includes an electro-optic crystal, the terahertz wave detecting element 40 receives the terahertz wave and the probe light output from the multiplexing unit 16, and birefringence is caused by the Pockels effect as the terahertz wave propagates. The probe light is induced and the polarization state of the probe light is changed by the birefringence, and the probe light is output. Since the amount of birefringence at this time depends on the electric field strength of the terahertz wave, the amount of change in the polarization state of the probe light in the terahertz wave detecting element 40 depends on the electric field strength of the terahertz wave.

  The polarization separation element 52 is, for example, a Wollaston prism, and receives the probe light output from the terahertz wave detection element 40 and passed through the quarter wavelength plate 51, and separates the input probe light into two orthogonal polarization components. And output. The photodetectors 53A and 53B include, for example, photodiodes, detect the powers of the two polarization components of the probe light polarized and separated by the polarization separation element 52, and differentiate the electric signals having values corresponding to the detected powers. Output to the dynamic amplifier 54.

  The differential amplifier 54 receives the electric signal output from each of the photodetectors 53A and 53B, and outputs an electric signal having a value corresponding to the difference between the two electric signals to the lock-in amplifier 55. The lock-in amplifier 55 synchronously detects the electrical signal output from the differential amplifier 54 at the repetition frequency of passing and blocking the pump light in the chopper 13. The signal output from the lock-in amplifier 55 has a value that depends on the electric field strength of the terahertz wave. In this manner, the correlation between the terahertz wave transmitted through the measurement object S and the probe light is detected, and the electric field amplitude of the terahertz wave is detected, so that information on the measurement object S can be obtained.

  The terahertz wave measuring device 8 operates as follows. The pulsed light output from the light source 11 is bifurcated by the branching unit 12 to be pump light and probe light. The pump light output from the branching unit 12 is sequentially reflected by the mirrors M <b> 1 to M <b> 3 and input to the terahertz wave generating element 20. The terahertz wave generating element 20 generates and outputs a terahertz wave in response to the input of pump light. The terahertz wave output from the terahertz wave generating element 20 passes through the measurement target portion S and is input to the multiplexing portion 16. On the other hand, the probe light output from the branching unit 12 is sequentially reflected by the mirrors M <b> 4 to M <b> 8, is linearly polarized by the polarizer 15, and is input to the multiplexing unit 16.

  The terahertz wave and the probe light input to the multiplexing unit 16 are combined by the multiplexing unit 16 so as to be coaxial with each other, and input to the terahertz wave detecting element 40 at substantially the same timing. In the terahertz wave detecting element 40 to which the terahertz wave and the probe light are input, birefringence is induced as the terahertz wave propagates, and the polarization state of the probe light changes due to the birefringence. The polarization state of the probe light in the terahertz wave detection element 40 is detected by the quarter wavelength plate 51, the polarization separation element 52, the photodetector 53A, the photodetector 53B, the differential amplifier 54, and the lock-in amplifier 55. The In this way, a change in the polarization state of the probe light in the terahertz wave detection element 40 is detected, and consequently, the electric field amplitude of the terahertz wave is detected, and the characteristic of the measurement object S is obtained.

  However, in such a transmission measurement method, since the absorption of terahertz waves by water is large, the measurement object S is usually limited to a dry solid. The total reflection terahertz wave measuring apparatus 9 according to the second comparative example described below can solve such a problem.

(Second comparative example)
Next, the total reflection terahertz wave measuring apparatus 9 according to the second comparative example will be described. FIG. 2 is a configuration diagram of the total reflection terahertz wave measuring apparatus 9 according to the second comparative example. A total reflection terahertz wave measuring device 9 shown in this figure acquires information on the measuring object S by a total reflection measurement method using a terahertz wave, and includes a light source 11, a branching unit 12, a chopper 13, an optical path length. Difference adjusting unit 14, polarizer 15, multiplexing unit 16, terahertz wave generating element 20, prism 30, terahertz wave detecting element 40, quarter wavelength plate 51, polarization separating element 52, photodetector 53A, photodetector 53B A differential amplifier 54 and a lock-in amplifier 55.

  Compared with the configuration of the terahertz wave measuring apparatus 8 according to the first comparative example shown in FIG. 1, the total reflection terahertz wave measuring apparatus 9 according to the second comparative example shown in FIG. The difference is that a prism 30 is provided. The prism 30 inputs the terahertz wave output from the terahertz wave generating element 20 to the incident surface 30a, propagates the input terahertz wave inside, totally reflects the reflected surface 30c, and the terahertz wave after being totally reflected. Is output from the output surface 30 b to the multiplexing unit 16. The prism 30 is a duff prism, and the chief ray of the terahertz wave input to the incident surface 30a and the chief ray of the terahertz wave output from the exit surface 30b are on a common straight line. The measuring object S is disposed on the reflecting surface 30 c of the prism 30.

  In the terahertz wave measuring device 9, the terahertz wave output from the terahertz wave generating element 20 is input to the incident surface 30 a of the prism 30, propagates through the prism 30 and is totally reflected by the reflecting surface 30 c of the prism 30. The At the time of the total reflection, an evanescent component of the terahertz wave is present in a portion of the measuring object S in the vicinity of the reflecting surface 30c. From this, the terahertz wave after being totally reflected by the reflecting surface 30c of the prism 30 acquires information on a portion of the measuring object S in the vicinity of the reflecting surface 30c. Then, the totally reflected terahertz wave propagates inside the prism 30 and is output to the outside from the emission surface 30 b of the prism 30. The terahertz wave output from the prism 30 is input to the multiplexing unit 16 together with the probe light that has passed through the probe optical system.

  The terahertz wave and the probe light input to the multiplexing unit 16 are combined by the multiplexing unit 16 so as to be coaxial with each other, and input to the terahertz wave detecting element 40 at substantially the same timing. In the terahertz wave detecting element 40 to which the terahertz wave and the probe light are input, birefringence is induced as the terahertz wave propagates, and the polarization state of the probe light changes due to the birefringence. The polarization state of the probe light in the terahertz wave detection element 40 is detected by the quarter wavelength plate 51, the polarization separation element 52, the photodetector 53A, the photodetector 53B, the differential amplifier 54, and the lock-in amplifier 55. The In this way, a change in the polarization state of the probe light in the terahertz wave detection element 40 is detected, and consequently, the electric field amplitude of the terahertz wave is detected, and the characteristic of the measurement object S is obtained.

  In such a total reflection measurement method, measurement is possible even if the measurement object S arranged on the reflection surface 30c of the prism 30 contains moisture. However, it is desirable that there is no or little moisture in the space where the terahertz wave propagates from the terahertz wave generating element 20 to the terahertz wave detecting element 40.

  In this total reflection measurement method, it is necessary to dispose the measurement object S on the reflection surface 30c of the prism 30 that totally reflects the terahertz wave. However, when the measurement object S is a fluid, it is difficult to perform stable measurement by arranging the fluid measurement object S on the reflecting surface 30c of the prism 30. Further, the evanescent component of the terahertz wave is irradiated to the measuring object S only once, and the measurement sensitivity is low. The total reflection terahertz wave measuring apparatus according to the present embodiment described below can solve such problems.

(First embodiment)
Next, the total reflection terahertz wave measuring apparatus 1 according to the first embodiment of the present invention will be described. FIG. 3 is a configuration diagram of the total reflection terahertz wave measuring apparatus 1 according to the first embodiment. The total reflection terahertz wave measuring apparatus 1 shown in this figure acquires information on the measuring object S by a total reflection measurement method using terahertz waves, and includes a light source 11, a branching unit 12, a chopper 13, an optical path length. Difference adjustment unit 14, polarizer 15, multiplexing unit 16, terahertz wave generation element 20, internal multiple total reflection prism 31, terahertz wave detection element 40, ¼ wavelength plate 51, polarization separation element 52, photodetector 53A, A photodetector 53B, a differential amplifier 54, and a lock-in amplifier 55 are provided.

  Compared with the configuration of the total reflection terahertz wave measuring apparatus 9 according to the second comparative example shown in FIG. 2, the total reflection terahertz wave measuring apparatus 1 according to the first embodiment shown in FIG. The difference is that an internal multiple total reflection prism 31 is provided. In the total reflection terahertz wave measuring apparatus 1, as shown in FIG. 4, a measurement object S that is a fluid is placed in a container 60, and an internal multiple total reflection prism 31 is inserted into the measurement object S. The

  The internal multiple total reflection prism 31 has an entrance surface 31a, an exit surface 31b, and four reflection surfaces 31c to 31f. The internal multiple total reflection prism 31 inputs the terahertz wave output from the terahertz wave generation element 20 and reflected by the mirror M9 to the incident surface 31a, propagates the input terahertz wave inside, and also reflects the four reflection surfaces 31c to 31c. The terahertz wave is totally reflected by 31 f and output to the multiplexing unit 16 from the emission surface 31 b through the mirror M 10.

The internal multiple total reflection prism 31 is transparent at the wavelength of the terahertz wave output from the terahertz wave generating element 20, and is made of a material having a refractive index higher than that of the measuring object S, for example, silicon. preferable. Silicon is transparent in the wavelength band of terahertz waves, and has a refractive index of 3.4 at a wavelength of 1 THz. For example, assuming that the main component of the measuring object S is water, the refractive index at a wavelength of 1 THz of water is 2.0. At this time, since the critical angle is 36 degrees (= sin ⁻¹ (2.0 / 3.4)), total reflection occurs when the incident angle is larger than this critical angle (for example, 45 degrees as shown). Similarly, total reflection occurs when the measuring object S is a gas.

  The internal multiple total reflection prism 31 is inserted into the measurement object S contained in the container 60, and the total reflection points on the three reflection surfaces 31 c to 31 e out of the four reflection surfaces 31 c to 31 f are in contact with the measurement object S. . The internal multiple total reflection prism 31 preferably has a polygonal column shape (for example, a hexagonal column shape as shown). In this case, the plurality of polygonal columnar side surfaces are any of the entrance surface, the exit surface, and the reflection surface, and the top surface and the bottom surface can be held by the holder.

  The total reflection terahertz wave measuring apparatus 1 operates as follows. The pulsed light output from the light source 11 is bifurcated by the branching unit 12 to be pump light and probe light. The pump light output from the branching unit 12 is sequentially reflected by the mirrors M <b> 1 to M <b> 3 and input to the terahertz wave generating element 20. The terahertz wave generating element 20 generates and outputs a terahertz wave in response to the input of pump light. The terahertz wave output from the terahertz wave generating element 20 is reflected by the mirror M9 and then input to the incident surface 31a of the internal multiple total reflection prism 31, and propagates through the internal multiple total reflection prism 31 and is internally multiplexed. Total reflection is performed on each of the reflection surfaces 31 c to 31 f of the total reflection prism 31.

  Among them, the evanescent component of the terahertz wave is present in the portion of the measuring object S in the vicinity of each reflecting surface during total reflection on each of the reflecting surfaces 31c to 31e. From this, the terahertz wave after being totally reflected by each of the reflection surfaces 31c to 31e of the internal multiple total reflection prism 31 acquires information on a portion of the measurement object S in the vicinity of each reflection surface. Then, the totally reflected terahertz wave is output from the emission surface 31 b of the internal multiple total reflection prism 31 to the outside. The terahertz wave output from the internal multiple total reflection prism 31 is reflected by the mirror M10 and input to the multiplexing unit 16 together with the probe light that has passed through the probe optical system.

  The terahertz wave and the probe light input to the multiplexing unit 16 are combined by the multiplexing unit 16 so as to be coaxial with each other, and input to the terahertz wave detecting element 40 at substantially the same timing. In the terahertz wave detecting element 40 to which the terahertz wave and the probe light are input, birefringence is induced as the terahertz wave propagates, and the polarization state of the probe light changes due to the birefringence. The polarization state of the probe light in the terahertz wave detection element 40 is detected by the quarter wavelength plate 51, the polarization separation element 52, the photodetector 53A, the photodetector 53B, the differential amplifier 54, and the lock-in amplifier 55. The In this way, a change in the polarization state of the probe light in the terahertz wave detection element 40 is detected, and consequently, the electric field amplitude of the terahertz wave is detected, and the characteristic of the measurement object S is obtained.

  The optical path length difference adjusting unit 14 adjusts the optical path length between the mirrors M4 and M7 and the mirrors M5 and M6, and adjusts the optical path length of the probe optical system, so that the terahertz input to the multiplexing unit 16 is achieved. The timing difference between the wave and the probe light is adjusted. As described above, the pulse width of the terahertz wave is generally about picoseconds, whereas the pulse width of the probe light is about femtoseconds, and the pulse width of the probe light is several orders of magnitude narrower than that of the terahertz wave. From this, the time waveform of the electric field amplitude of the pulsed terahertz wave is obtained by sweeping the incident timing of the probe light to the terahertz wave detecting element 40 by the optical path length difference adjusting unit 14.

  As described above, the total reflection terahertz wave measuring apparatus 1 according to the first embodiment superimposes information about the measurement object S arranged on each of the plurality of reflection surfaces of the internal multiple total reflection prism 31 to generate a terahertz wave. It is acquired by the evanescent component of the terahertz wave generated during total reflection of the terahertz wave. From this, even if the measuring object S is a fluid, it can be measured easily and with high sensitivity. Further, since the reflection angle and the number of reflections can be clarified, quantitative evaluation is possible.

  In addition, it is desirable that there is no or little moisture in the space where the terahertz wave propagates from the terahertz wave generating element 20 to the terahertz wave detecting element 40. Therefore, it is preferable to perform a nitrogen purge in this space.

(Second Embodiment)
Next, the total reflection terahertz wave measuring apparatus 2 according to the second embodiment of the present invention will be described. FIG. 5 is a configuration diagram of the total reflection terahertz wave measuring apparatus 2 according to the second embodiment. The total reflection terahertz wave measuring apparatus 2 shown in this figure acquires information on the measuring object S by a total reflection measurement method using terahertz waves, and includes a light source 11, a branching unit 12, a chopper 13, an optical path length. Difference adjustment unit 14, polarizer 15, beam splitter 17, terahertz wave generating element 20, internal multiple total reflection prism 31, terahertz wave detecting element 40, quarter wavelength plate 51, polarization separating element 52, photodetector 53A, light A detector 53B, a differential amplifier 54, and a lock-in amplifier 55 are provided.

  Compared with the configuration of the total reflection terahertz wave measuring apparatus 1 according to the first embodiment shown in FIG. 3, the total reflection terahertz wave measuring apparatus 2 according to the second embodiment shown in FIG. The difference is that the terahertz wave generating element 20 is integrally provided on the incident surface 31 a of the prism 31, and the terahertz wave detecting element 40 is integrally provided on the emission surface 31 b of the internal multiple total reflection prism 31. Further, the difference is that a beam splitter 17 is provided instead of the multiplexing unit 16. In the total reflection terahertz wave measuring apparatus 2, as shown in FIG. 6, a measurement object S that is a fluid is placed in a container 60, and an internal multiple total reflection prism 31 is inserted into the measurement object S. The

  When integrating the terahertz wave generation element 20 and the terahertz wave detection element 40 with the internal multiple total reflection prism 31, the terahertz wave generation element 20 is bonded to the incident surface 31a of the internal multiple total reflection prism 31 with an adhesive, Further, the terahertz wave detecting element 40 is bonded to the emission surface 31b of the internal multiple total reflection prism 31 with an adhesive. The adhesive used at this time is transparent at the wavelength of the terahertz wave, and is an intermediate between the refractive indexes of the terahertz wave generating element 20 and the terahertz wave detecting element 40 and the refractive index of the internal multiple total reflection prism 31. Or it is preferable to have an equivalent refractive index.

  Further, it is preferable that the reflectance is high at the wavelength of the probe light at the joint position between the reflection surface 31 b of the internal total reflection prism 31 and the terahertz wave detection element 40. A dielectric multilayer film may be formed on the reflecting surface 31b, and thus, it may be transparent to the terahertz wave and have a high reflectance with respect to the probe light wavelength.

  The total reflection terahertz wave measuring apparatus 2 operates as follows. The pulsed light output from the light source 11 is bifurcated by the branching unit 12 to be pump light and probe light. The pump light output from the branching unit 12 is sequentially reflected by the mirrors M1 to M3 and the mirror M9 and input to the terahertz wave generating element 20 provided integrally with the incident surface 31a of the internal multiple total reflection prism 31. Is done. The terahertz wave generating element 20 generates and outputs a terahertz wave in response to the input of pump light. The terahertz wave output from the terahertz wave generating element 20 is immediately input to the incident surface 31a of the internal multiple total reflection prism 31 without being propagated in space, and propagates through the internal multiple total reflection prism 31 and is subjected to internal multiple total reflection. Total reflection is performed on each of the reflecting surfaces 31 c to 31 f of the prism 31.

  Among them, the evanescent component of the terahertz wave is present in the portion of the measuring object S in the vicinity of each reflecting surface during total reflection on each of the reflecting surfaces 31c to 31e. From this, the terahertz wave after being totally reflected by each of the reflection surfaces 31c to 31e of the internal multiple total reflection prism 31 acquires information on a portion of the measurement object S in the vicinity of each reflection surface. Then, the totally reflected terahertz wave is output from the exit surface 31b of the internal multiple total reflection prism 31 and immediately integrated with the output surface 31b of the internal multiple total reflection prism 31 without being propagated in space. Input to the terahertz wave detection element 40.

  On the other hand, the probe light output from the branching unit 12 is sequentially reflected by the mirrors M4 to M8, the beam splitter 17 and the mirror M10 and input to the terahertz wave detecting element 40. The terahertz wave input from the mirror M10 to the terahertz wave detection element 40 passes through the terahertz wave detection element 40, is reflected by the emission surface 31b of the internal multiple total reflection prism 31, and passes through the terahertz wave detection element 40 again. Output to the mirror M10.

  The terahertz wave and the probe light are input to the terahertz wave detecting element 40 at substantially the same timing so as to be coaxial with each other. In the terahertz wave detecting element 40 to which the terahertz wave and the probe light are input, birefringence is induced as the terahertz wave propagates, and the polarization state of the probe light changes due to the birefringence. The probe light output from the terahertz wave detection element 40 to the mirror M10 is reflected by the mirror M10 and passes through the beam splitter 17. The polarization state of the probe light is detected by the quarter-wave plate 51, the polarization separation element 52, the photodetector 53A, the photodetector 53B, the differential amplifier 54, and the lock-in amplifier 55. In this way, a change in the polarization state of the probe light in the terahertz wave detection element 40 is detected, and consequently, the electric field amplitude of the terahertz wave is detected, and the characteristic of the measurement object S is obtained.

  As described above, the total reflection terahertz wave measuring apparatus 2 according to the second embodiment uses the information about the measurement object S arranged on each of the plurality of reflection surfaces of the internal multiple total reflection prism 31 as the total reflection of the terahertz wave. It is acquired by the evanescent component of the terahertz wave generated at the time. From this, even if the measuring object S is a fluid, it can be measured easily and with high sensitivity. Further, since the terahertz wave generating element 20 and the terahertz wave detecting element 40 are provided integrally with the internal multiple total reflection prism 31, they are easy to handle, and this point can be easily measured. Further, the size can be reduced. Further, since the terahertz wave propagates through the internal multiple total reflection prism 31 without spatial propagation from the terahertz wave generating element 20 to the terahertz wave detecting element 40, it is not necessary to perform nitrogen purge, and this point is also easy. It can be measured and can be miniaturized. Furthermore, since the loss of the terahertz wave on each of the entrance surface 31a and the exit surface 31b of the internal multiple total reflection prism 31 is reduced, it is possible to measure with high sensitivity also in this respect.

  Next, a modification of the total reflection terahertz wave measuring apparatus 2 according to the second embodiment will be described. The modification described below relates to the internal multiple total reflection prism shown in FIG. 6 and its peripheral configuration.

  FIG. 7 is a diagram illustrating an internal multiple total reflection prism in the total reflection terahertz wave measuring apparatus 2 according to the second embodiment and a modification of the periphery. The internal multiple total reflection prism 32 shown in this figure is used in place of the internal multiple total reflection prism 31 in FIG. 5, and the terahertz wave generating element 20 is integrally provided on the incident surface 32a. The terahertz wave detecting element 40 is integrally provided on the emission surface 32b. In the internal multiple total reflection prism 32, a lens 32p is formed in the vicinity of the entrance surface 32a, and a lens 32q is formed in the vicinity of the exit surface 32b. The lens 32 p has a collimating effect on the terahertz wave generated by the terahertz wave generating element 20 and propagating through the internal multiple total reflection prism 32. The lens 32q has a condensing effect on the terahertz wave that propagates through the internal multiple total reflection prism 32 and is output to the terahertz wave detecting element 40.

  The terahertz wave output from the terahertz wave generating element 20 is immediately input to the incident surface 32a of the internal multiple total reflection prism 32 without being propagated in space, collimated by the lens 32p, and propagates inside the internal multiple total reflection prism 32. At the same time, the light is totally reflected at each of the reflection surfaces 32c to 32f of the internal multiple total reflection prism 32. Among them, the evanescent component of the terahertz wave is present in a portion of the measuring object S in the vicinity of each reflecting surface during total reflection at each of the reflecting surfaces 32c to 32e. From this, the terahertz wave after being totally reflected by each of the reflection surfaces 32c to 32e of the internal multiple total reflection prism 32 acquires information on a portion of the measurement object S in the vicinity of each reflection surface. Then, the totally reflected terahertz wave is collected by the lens 32q and output from the exit surface 32b, and immediately integrated with the exit surface 32b of the internal multiple total reflection prism 32 without being propagated in space. Input to the terahertz wave detection element 40.

  Such an internal multiple total reflection prism 32 can be manufactured through a process as illustrated in FIG. That is, a prism 32A having the same outer shape as that of the internal multiple total reflection prism 32 is prepared ((a) in the figure), and the prism 32A is cut at a position indicated by a broken line in the figure to form members 32B, 32C, and 32D. (FIG. 5B). At this time, the cutting position is a center position where the lenses 32p and 32q should be provided. Next, a recess is formed in one of the cut surfaces of the members 32B, 32C, and 32D (FIG. 3C), and the recess is filled with resin or powder, and the members 32B, 32C, and 32D are joined together. Then, the resin is cured or the powder is compacted. In this way, the internal multiple total reflection prism 32 can be manufactured.

  The shapes of the lenses 32p and 32q depend on the relationship between the refractive index of the resin filled in the concave portion and the refractive index of the prism 32A. That is, when the refractive index of the resin is higher than the refractive index of the prism 32A at the terahertz wavelength, the lenses 32p and 32q are convex lenses. Conversely, when the refractive index of the resin is lower than the refractive index of the prism 32A, the shape of the lenses 32p and 32q is a concave lens. For example, the prism 32A is made of silicon, and the resin filled in the recesses is made of polyethylene.

  FIG. 9 is a diagram for explaining an internal multiple total reflection prism in the total reflection terahertz wave measuring apparatus 2 according to the second embodiment and a modification of the periphery. The internal multiple total reflection prism 33 shown in this figure is used in place of the internal multiple total reflection prism 31 in FIG. 5, and the terahertz wave generating element 20 is integrally provided on the incident surface 33a. The terahertz wave detecting element 40 is integrally provided on the emission surface 33b. The internal multiple total reflection prism 33 has a lens 33p formed on the entrance surface 33a and a lens 33q formed on the exit surface 33b. The lens 33 p has a collimating effect on the terahertz wave generated by the terahertz wave generating element 20 and propagating through the internal multiple total reflection prism 33. The lens 33q has a condensing effect on the terahertz wave that propagates through the internal multiple total reflection prism 33 and is output to the terahertz wave detecting element 40.

  The lens 33p is formed by filling a concave portion formed on the incident surface 33a with a resin or the like. The lens 33q is a lens in which a recess formed in the emission surface 33b is filled with resin or the like. The shapes of the lenses 33p and 33q depend on the relationship between the refractive index of the resin filled in the concave portion and the refractive index of the prism 33. That is, when the refractive index of the resin is higher than the refractive index of the prism 33 at the terahertz wavelength, the shapes of the lenses 33p and 33q are convex lenses. Conversely, when the refractive index of the resin is lower than the refractive index of the prism 33, the lenses 33p and 33q are concave lenses.

  The terahertz wave output from the terahertz wave generating element 20 is immediately input to the incident surface 33a of the internal multiple total reflection prism 33 without being propagated in space, collimated by the lens 33p, and propagates inside the internal multiple total reflection prism 33. At the same time, the internal multiple total reflection prism 33 is totally reflected by each of the reflection surfaces 33c to 33f. Among them, the evanescent component of the terahertz wave is present in the portion of the measuring object S in the vicinity of each reflecting surface during total reflection at each of the reflecting surfaces 33c to 33e. From this, the terahertz wave after being totally reflected by each of the reflection surfaces 33c to 33e of the internal multiple total reflection prism 33 acquires information on a portion of the measurement object S in the vicinity of each reflection surface. Then, the totally reflected terahertz wave is collected by the lens 33q and output from the exit surface 33b, and is immediately integrated with the exit surface 33b of the internal multiple total reflection prism 33 without being propagated in space. Input to the terahertz wave detection element 40.

  In addition, a Fresnel lens may be formed in or on the entrance surface or exit surface side of the internal multiple total reflection prism. When a Fresnel lens is formed inside, it can be formed by laser processing. Also, in the same manner as described in FIG. 8, the prism is cut and a Fresnel lens is formed on the cut surface. It can be joined to the original. By forming the lens in this manner, the terahertz wave can be collimated or condensed, and an image can be transferred.

(Third embodiment)
Next, a total reflection terahertz wave measuring apparatus 3 according to a third embodiment of the present invention will be described. FIG. 10 is a configuration diagram of the total reflection terahertz wave measuring apparatus 3 according to the third embodiment. The total reflection terahertz wave measuring device 3 shown in this figure acquires information on the measuring object S by a total reflection measurement method using a terahertz wave, and includes a light source 11, a branching unit 12, and an optical path length difference adjusting unit. 14, a terahertz wave generation element 21, an internal multiple total reflection prism 33, a terahertz wave detection element 41, a signal generation unit 56, and a synchronization detection unit 57.

  In the total reflection terahertz wave measuring device 3, as shown in FIG. 11, the terahertz wave generating element 21 is integrally provided on the incident surface 33 a of the internal multiple total reflection prism 33, and the output surface of the internal multiple total reflection prism 33. A terahertz wave detecting element 41 is integrally provided at 33b. The internal multiple total reflection prism 33 has the configuration shown in FIG. Further, as each of the terahertz wave generating element 21 and the terahertz wave detecting element 41, a photoconductive antenna element as shown in FIG. 12 is used.

  A photoconductive antenna element 100 shown in FIG. 12 is used as the terahertz wave generating element 21 or the terahertz wave detecting element 41, and is formed on, for example, a semi-insulating GaAs substrate 101 and the GaAs substrate 101. And a pair of electrodes 103 and 104 formed on the GaAs layer 102. The GaAs layer 102 is epitaxially grown at a low temperature (for example, 200 to 250 ° C.) by MBE, and has a thickness of 1 to 3 μm, for example. The electrode 103 and the electrode 104 are ohmic electrodes such as AuGe / Au, the length of the antenna is, for example, 20 μm to 2 mm, and the distance between them is, for example, 3 to 10 μm. The GaAs layer 102 formed by low temperature epitaxial growth has a short carrier lifetime, high carrier mobility, and high impedance.

  In the photoconductive antenna element 100 as the terahertz wave generating element 21, when a voltage is applied between the electrode 103 and the electrode 104, pump light is applied to the region of the GaAs layer 102 between the electrode 103 and the electrode 104. When irradiated, electron-hole pairs are generated in the GaAs layer 102. The electrons move by being accelerated by a voltage applied between the electrode 103 and the electrode 104. Thereby, a current is generated between the electrode 103 and the electrode 104, and a terahertz wave is generated. A voltage having a constant period is applied by the signal generator 56 between the electrode 103 and the electrode 104 of the photoconductive antenna element 100 as the terahertz wave generating element 21.

  In the photoconductive antenna element 100 as the terahertz wave detection element 41, a current representing the correlation between the electrodes 103 and 104 is generated in response to the incidence of the terahertz wave and the probe light. Based on this correlation, the spectrum of the terahertz wave can be obtained, and information on the measurement object can be obtained. The current generated between the electrode 103 and the electrode 104 of the photoconductive antenna element 100 as the terahertz wave detecting element 41 is caused by the synchronization detecting unit 57 to generate a terahertz wave generation period (that is, the signal generating unit 56) in the terahertz wave generating element 21. Is detected in synchronization with the period of voltage application.

  The total reflection terahertz wave measuring apparatus 3 operates as follows. The laser light output from the light source 11 is bifurcated by the branching unit 12 to be pump light and probe light. The pump light output from the branching unit 12 is sequentially reflected by the mirrors M1 to M3 and the mirror M9, and input to the terahertz wave generating element 21 provided integrally with the incident surface 33a of the internal multiple total reflection prism 33. Is done. In the photoconductive antenna element 100 as the terahertz wave generating element 21, a voltage having a constant period is applied between the electrode 103 and the electrode 104 by the signal generating unit 56, and pump light is applied between the electrode 103 and the electrode 104. As a result, a terahertz wave is generated.

  The terahertz wave output from the terahertz wave generating element 21 is immediately input to the incident surface 33a of the internal multiple total reflection prism 33 without being propagated in space, collimated by the lens 33p, and propagates inside the internal multiple total reflection prism 33. At the same time, the internal multiple total reflection prism 33 is totally reflected by each of the reflection surfaces 33c to 33f. Among them, the evanescent component of the terahertz wave is present in the portion of the measuring object S in the vicinity of each reflecting surface during total reflection at each of the reflecting surfaces 33c to 33e. From this, the terahertz wave after being totally reflected by each of the reflection surfaces 33c to 33e of the internal multiple total reflection prism 33 acquires information on a portion of the measurement object S in the vicinity of each reflection surface. Then, the totally reflected terahertz wave is collected by the lens 33q and output from the exit surface 33b, and is immediately integrated with the exit surface 33b of the internal multiple total reflection prism 33 without being propagated in space. Input to the terahertz wave detection element 41.

  The probe light output from the branching unit 12 and sequentially reflected by the mirrors M4 to M8, M11, and M10 is input between the electrode 103 and the electrode 104 of the photoconductive antenna element 100 as the terahertz wave detecting element 41. The The terahertz wave output from the exit surface 33 b of the internal multiple total reflection prism 33 is also input between the electrode 103 and the electrode 104 of the photoconductive antenna element 100 as the terahertz wave detection element 41.

  In the photoconductive antenna element 100 as the terahertz wave detection element 41, a current representing the correlation between the electrodes 103 and 104 is generated in response to the incidence of the terahertz wave and the probe light. This current is detected by the synchronization detector 57 in synchronization with the period of voltage application by the signal generator 56. As a result, the spectrum of the terahertz wave is obtained, and information on the measurement object S is obtained.

  The total reflection terahertz wave measuring apparatus 3 according to the third embodiment can also exhibit the same effect as the effect exhibited by the total reflection terahertz wave measuring apparatus 2 according to the second embodiment. Similarly to FIG. 2, detection can be performed by chopping the pump light. At this time, the signal generator 56 outputs a DC voltage and can be detected by the synchronization detector 57 in synchronization with the optical chopper.

  Next, a modification of the total reflection terahertz wave measuring apparatus 3 according to the third embodiment will be described. The modification described below relates to the internal multiple total reflection prism shown in FIG. 11 and its peripheral configuration. FIG. 13 is a diagram for explaining a modified example of the internal multiple total reflection prism and its surroundings in the total reflection terahertz wave measuring apparatus 3 according to the third embodiment. As shown in this figure, an optical fiber 71 for pump light that guides pump light to the terahertz wave generating element 21 provided on the incident surface 33 a of the internal multiple total reflection prism 33 is provided, and the internal multiple total reflection prism 33 is provided. An optical fiber 72 for probe light that guides probe light to the terahertz wave detecting element 41 provided on the emission surface 33b of the optical fiber is provided.

  In addition, it is preferable that the portion including the terahertz wave generating element 21 and the terahertz wave detecting element 41 is provided with a waterproof measure including the tip portions of the optical fibers 71 and 72. By doing so, it becomes possible to completely immerse the internal multiple total reflection prism 33 together with the terahertz wave generation element 21 and the terahertz wave detection element 41 in the measuring object S, and the upper surface of the internal multiple total reflection prism 33 is obtained. The evanescent component of the terahertz wave on the reflecting surface 33f can also be used effectively.

(Fourth embodiment)
Next, a total reflection terahertz wave measuring apparatus 4 according to a fourth embodiment of the present invention will be described. FIG. 14 is a configuration diagram of the total reflection terahertz wave measuring apparatus 4 according to the fourth embodiment. The total reflection terahertz wave measuring device 4 shown in this figure acquires information on the measuring object S by a total reflection measurement method using terahertz waves, and includes a light source 11, a branching unit 12, a chopper 13, an optical path length. Difference adjustment unit 14, polarizer 15, multiplexing unit 16, terahertz wave generation element 20, internal multiple total reflection prism 34, terahertz wave detection element 40, quarter wavelength plate 51, polarization separation element 52, photodetector 53A, A photodetector 53B, a differential amplifier 54, and a lock-in amplifier 55 are provided.

  Compared with the configuration of the total reflection terahertz wave measuring apparatus 1 according to the first embodiment shown in FIG. 3, the total reflection terahertz wave measuring apparatus 4 according to the fourth embodiment shown in FIG. The difference is that an internal multiple total reflection prism 34 is provided instead of the prism 31. Further, in the total reflection terahertz wave measuring device 4, the measurement object S that is a fluid is placed in the container 60, and the internal multiple total reflection prism 34 is inserted into the measurement object S.

  The internal multiple total reflection prism 34 has an entrance surface 34a, an exit surface 34b, and reflection surfaces 34c to 34e. The entrance surface 34a and the exit surface 34b are parallel to each other. The reflecting surface 34c is perpendicular to the entrance surface 34a and the exit surface 34b. The reflective surface 34d and the reflective surface 34e are on the side facing the reflective surface 34c, and constitute a V-shaped notch. Each of the entrance surface 34a and the exit surface 34b acts as a reflection surface for a terahertz wave that propagates inside and enters at an incident angle that is equal to or greater than the critical angle.

  In the internal multiple total reflection prism 34, the terahertz wave output from the terahertz wave generating element 20 is input perpendicularly to the incident surface 34a and introduced into the interior, and after being totally reflected by the reflecting surface 34d, the incident surface. The light is totally reflected at 34a, the emission surface 34b, and the reflection surface 34c. Then, the terahertz wave after being totally reflected by the reflection surface 34e is output perpendicularly to the emission surface 34b.

  The total reflection terahertz wave measuring apparatus 4 according to the fourth embodiment using such an internal multiple total reflection prism 34 operates in the same manner as the operation of the total reflection terahertz wave measuring apparatus 1 according to the first embodiment. The effect similar to the effect which the total reflection terahertz wave measuring apparatus 1 which concerns on 1st Embodiment has can be show | played.

  The total reflection position of the terahertz wave on the reflection surface 34c is preferably at the center position between the entrance surface 34a and the exit surface 34b. In this case, the chief ray of the terahertz wave input to the incident surface 34a of the internal multiple total reflection prism 34 and the chief ray of the terahertz wave output from the output surface 34b of the internal multiple total reflection prism 34 are on a common straight line. It will be in. Thus, if either the internal multiple total reflection prism 34 or the measurement object is selected and arranged at the position of the internal multiple total reflection prism 34, the total reflection measurement method and the transmission measurement method are switched. be able to.

  The reflective surface 34d and the reflective surface 34e constituting the V-shaped notch are preferably deposited with a metal film in order to reflect the terahertz wave with high reflectivity. In addition, it is preferable that a metal film is deposited on the reflecting surface 34c. In this case, the reflection of the terahertz wave on the reflecting surface 34c does not contribute to the spectroscopic result, and the incident angle of the terahertz wave on the reflecting surface 34c is arbitrary. Therefore, the degree of freedom of the incident angle of the terahertz wave on each of the entrance surface 34a and the exit surface 34b is increased.

  In the terahertz wave incident region of the incident surface 34a, a polarizer that transmits a polarized component in a specific direction in the input terahertz wave may be provided. Further, the reflecting surface 34d may be provided with a polarizer that reflects a polarized light component in a specific direction in the terahertz wave. As such a polarizer, for example, a wire grid polarizer in which a plurality of metal wires are arranged in parallel is preferable.

  FIG. 15 is a diagram illustrating an internal multiple total reflection prism 35 that can be used in place of the internal multiple total reflection prism 34 in the total reflection terahertz wave measuring apparatus 4 according to the fourth embodiment. The internal multiple total reflection prism 35 also has an entrance surface 35a, an exit surface 35b, and reflection surfaces 35c to 35e. The entrance surface 35a and the exit surface 35b are parallel to each other. The reflection surface 35c is perpendicular to the entrance surface 35a and the exit surface 35b. The reflective surface 35d and the reflective surface 35e are on the side facing the reflective surface 35c, and constitute a V-shaped notch. Each of the entrance surface 35a and the exit surface 35b acts as a reflection surface for the terahertz wave propagating inside.

  Also in the internal multiple total reflection prism 35, the terahertz wave output from the terahertz wave generating element 20 is input perpendicularly to the incident surface 35a and introduced into the interior, and is totally reflected by the reflecting surface 35d, and then the incident surface. 35a is totally reflected at the exit surface 35b and the reflection surface 35c. Then, the terahertz wave after being totally reflected by the reflection surface 35e is output perpendicularly to the emission surface 35b.

  In particular, in the internal multiple total reflection prism 35, each of the reflection surface 35d and the reflection surface 35e constituting the V-shaped notch has an inclination of 22.5 degrees with respect to the opposite reflection surface 35c. . Thereby, each of the reflective surface 35d and the reflective surface 35e can totally reflect the terahertz wave even if the metal film is not deposited. Further, the incident angle of the terahertz wave at each of the incident surface 35a, the emitting surface 35b, and the reflecting surface 35c is 45 degrees.

  In each of the internal multiple total reflection prisms 34 and 35, a terahertz wave generating element may be integrally provided in the terahertz wave incident region of the incident surface, or a lens for collimating the terahertz wave is provided. Alternatively, an optical fiber that guides the pump light to the terahertz wave generating element may be connected. In each of the internal multiple total reflection prisms 34 and 35, a terahertz wave detection element may be integrally provided in the terahertz wave emission region of the emission surface, or a lens that collects the terahertz wave is provided. Alternatively, an optical fiber that guides the probe light to the terahertz wave detecting element may be connected.

(Fifth embodiment)
Next, a total reflection terahertz wave measuring apparatus according to a fifth embodiment of the present invention will be described. In the total reflection terahertz wave measuring apparatus according to the fifth embodiment described below, moving means for moving one of the fluid as the measurement object and the internal multiple total reflection prism relative to the other is provided. Yes. In the following, the internal multiple total reflection prism and the surroundings will be mainly described.

  The total reflection terahertz wave measuring apparatus shown in FIG. 16 moves the container 60 in which the measuring object S is placed in addition to the configuration of the total reflection terahertz wave measuring apparatus 1 according to the first embodiment shown in FIG. A stage 80 and a belt conveyor 81 are provided as moving means. In the drawing, an optical system 1A is an optical system of pump light, probe light, and terahertz waves from the light source 11 to the photodetectors 53A and 53B in the configuration of the total reflection terahertz wave measuring device 1 (however, internal multiplexing) Including the total reflection prism 31). The internal multiple total reflection prism 31 is fixed to the optical system 1A by a support tool 82, and its position is fixed. The container 60 in which the measuring object S is placed is placed on the stage 80 and horizontally moves on the belt conveyor 81, and moves up and down with the stage 80 when the belt conveyor 81 reaches a predetermined position. When the stage 80 is moved upward together with the stage 80, the internal multiple total reflection prism 31 is inserted into the measuring object S placed in the container 60 placed on the stage 80, and the measurement is performed. Moves downward. In this way, the measuring object S placed in each of the plurality of containers 60 is sequentially measured.

  The total reflection terahertz wave measuring apparatus shown in FIG. 17 includes the configuration (FIG. 10) of the total reflection terahertz wave measuring apparatus 3 according to the third embodiment including the internal multiple total reflection prism 33 shown in FIG. There is a support 83 attached to the internal multiple total reflection prism 33. A terahertz wave generating element 21 is integrally provided on the incident surface of the internal multiple total reflection prism 33, and an optical fiber 71 for pumping light that guides pump light to the terahertz wave generating element 21 is provided. A terahertz wave detecting element 41 is integrally provided on the exit surface of the internal multiple total reflection prism 33, and a probe light optical fiber 72 that guides probe light to the terahertz wave detecting element 41 is provided. The support 83 is fixed to a surface that is not any of the entrance surface, the exit surface, and the reflection surface of the internal multiple total reflection prism 33. In this case, by moving the internal multiple total reflection prism 33 with the support 33, the internal multiple total reflection prism 33 is inserted into the measurement target portion S in the container 60 and measurement is performed. By completely immersing the internal multiple total reflection prism 33 in the measuring object S, the evanescent component of the terahertz wave on the reflection surface, which is the upper surface of the internal multiple total reflection prism 33, can be effectively used.

  The total reflection terahertz wave measuring apparatus shown in FIG. 18 includes the configuration (FIG. 10) of the total reflection terahertz wave measuring apparatus 3 according to the third embodiment including the internal multiple total reflection prism 33 shown in FIG. The internal multiple total reflection prism 33 can be moved up and down by a moving mechanism 84. The container 60 in which the measurement object S is placed moves horizontally on the belt conveyor 81. When a certain container 60 comes below the internal multiple total reflection prism 33, the internal multiple total reflection prism 33 is moved downward by the moving mechanism 84 and inserted into the measuring object S contained in the container 60. The measurement is performed, and when the measurement is completed, the moving mechanism 84 moves upward. The total reflection terahertz wave measuring apparatus shown in FIG. 19 includes the configuration (FIG. 10) of the total reflection terahertz wave measuring apparatus 3 according to the third embodiment including the internal multiple total reflection prism 33 shown in FIG. In addition, the internal multiple total reflection prism 33 is inserted into the measuring object S flowing in the basket 61 by the moving mechanism 84. In this case, the measurement object S is moved and measured by flowing through the ridge 81.

  The total reflection terahertz wave measuring apparatus shown in FIG. 20 includes the configuration (FIG. 14) of the total reflection terahertz wave measuring apparatus 4 according to the fourth embodiment including the internal multiple total reflection prism 35 shown in FIG. In addition, the internal multiple total reflection prism 35 is inserted into the measuring object S flowing in the basket 61. In this case, the measurement object S is moved and measured by flowing through the ridge 81. Further, as shown in FIG. 21, the terahertz wave generating element 20 is integrally provided on the incident surface of the internal multiple total reflection prism 35, and the terahertz wave detecting element 40 is integrally formed on the output surface of the internal multiple total reflection prism 35. May be provided.

It is a lineblock diagram of terahertz wave measuring device 8 concerning the 1st comparative example. It is a block diagram of the total reflection terahertz wave measuring apparatus 9 which concerns on a 2nd comparative example. It is a lineblock diagram of total reflection terahertz wave measuring device 1 concerning a 1st embodiment. It is a figure explaining the internal multiple total reflection prism 31 in the total reflection terahertz wave measuring apparatus 1 which concerns on 1st Embodiment, and the said periphery. It is a block diagram of the total reflection terahertz wave measuring apparatus 2 which concerns on 2nd Embodiment. It is a figure explaining the internal multiple total reflection prism 31 in the total reflection terahertz wave measuring apparatus 2 which concerns on 2nd Embodiment, and the said periphery. It is a figure explaining the internal multiple total reflection prism in the total reflection terahertz wave measuring apparatus 2 which concerns on 2nd Embodiment, and the modification of the said periphery. 5 is a diagram illustrating a manufacturing process of the internal multiple total reflection prism 32. FIG. It is a figure explaining the internal multiple total reflection prism in the total reflection terahertz wave measuring apparatus 2 which concerns on 2nd Embodiment, and the modification of the said periphery. It is a block diagram of the total reflection terahertz wave measuring apparatus 3 which concerns on 3rd Embodiment. It is a figure explaining the internal multiple total reflection prism 33 in the total reflection terahertz wave measuring apparatus 3 which concerns on 3rd Embodiment, and the said periphery. It is a perspective view of a photoconductive antenna element. It is a figure explaining the internal multiple total reflection prism in the total reflection terahertz wave measuring apparatus 3 which concerns on 3rd Embodiment, and the modification of the said periphery. It is a block diagram of the total reflection terahertz wave measuring apparatus 4 which concerns on 4th Embodiment. It is a figure explaining the internal multiple total reflection prism 35 which can be used in the total reflection terahertz wave measuring apparatus 4 which concerns on 4th Embodiment. It is a block diagram of the total reflection terahertz wave measuring device which concerns on 5th Embodiment. It is a block diagram of the total reflection terahertz wave measuring device which concerns on 5th Embodiment. It is a block diagram of the total reflection terahertz wave measuring device which concerns on 5th Embodiment. It is a block diagram of the total reflection terahertz wave measuring device which concerns on 5th Embodiment. It is a block diagram of the total reflection terahertz wave measuring device which concerns on 5th Embodiment. It is a block diagram of the total reflection terahertz wave measuring device which concerns on 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1-4 ... Total reflection terahertz wave measuring apparatus, 11 ... Light source, 12 ... Branch part, 13 ... Chopper, 14 ... Optical path length difference adjustment part, 15 ... Polarizer, 16 ... Multiplexing part, 17 ... Beam splitter, 20, DESCRIPTION OF SYMBOLS 21 ... Terahertz wave generation element, 31-35 ... Internal multiple total reflection prism, 40, 41 ... Terahertz wave detection element, 51 ... 1/4 wavelength plate, 52 ... Polarization separation element, 53A, 53B ... Photo detector, 54 ... Differential amplifier 55 ... Lock-in amplifier 56 ... Signal generator 57 ... Synchronization detector 60 ... Container 71, 72 Optical fiber M1-M11 Mirror S ... Measurement object

Claims (10)

A light source that outputs light;
A branching unit that splits the light output from the light source into two, and outputs one of the two branched light as pump light and the other as probe light;
A terahertz wave generating element that generates and outputs a terahertz wave by inputting the pump light output from the branch unit; and
The terahertz wave output from the terahertz wave generating element is input to the incident surface, the input terahertz wave is propagated inside and totally reflected by a plurality of reflecting surfaces, and the terahertz wave is output from the emitting surface to the outside. An internal multiple total reflection prism;
A terahertz wave detection element that inputs a terahertz wave output from the exit surface of the internal multiple total reflection prism and a probe light output from the branching unit and detects a correlation between the terahertz wave and the probe light When,
With
Information about the measurement object disposed on each of the plurality of reflection surfaces of the internal multiple total reflection prism is acquired by an evanescent component of the terahertz wave generated during total reflection of the terahertz wave.
A total reflection terahertz wave measuring device.   Optical path length for adjusting the difference between the optical path of the pump light and the terahertz wave from the branching section to the terahertz wave detecting element and the optical path of the probe light from the branching section to the terahertz wave detecting element The total reflection terahertz wave measuring apparatus according to claim 1, further comprising a difference adjusting unit.   2. The total reflection terahertz wave measuring apparatus according to claim 1, wherein the terahertz wave generating element is integrally provided on the incident surface of the internal multiple total reflection prism.   The total reflection terahertz wave measuring apparatus according to claim 3, further comprising an optical fiber for pump light that guides pump light to the terahertz wave generation element provided on the incident surface of the internal multiple total reflection prism.   2. The optical element having a collimating effect on a terahertz wave propagating through the internal multiple total reflection prism is formed on the incident surface side of the internal multiple total reflection prism. The total reflection terahertz wave measuring apparatus described.   2. The total reflection terahertz wave measuring device according to claim 1, wherein the terahertz wave detecting element is integrally provided on the emission surface of the internal multiple total reflection prism.   The total reflection terahertz wave measuring apparatus according to claim 6, further comprising a probe light optical fiber for guiding probe light to the terahertz wave detecting element provided on the emission surface of the internal multiple total reflection prism.   The optical element which has a condensing effect with respect to the terahertz wave propagating through the inside of the internal multiple total reflection prism is formed on the exit surface side of the internal multiple total reflection prism. The total reflection terahertz wave measuring device according to 1.   The chief ray of the terahertz wave input to the incident surface of the internal multiple total reflection prism and the chief ray of the terahertz wave output from the output surface of the internal multiple total reflection prism are on a common straight line. The total reflection terahertz wave measuring apparatus according to claim 1. The total reflection terahertz wave measuring apparatus according to claim 1, further comprising moving means for moving one of the fluid as the measurement object and the internal multiple total reflection prism relative to the other.

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