JP2014174154A - Terahertz wave measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote cooling or heat radiation of a generating element and the like for generating terahertz wave.SOLUTION: A terahertz wave measuring device (100) has: generation means (110) generating a terahertz wave by being irradiated with a first laser beam (LB1); detection means (130) detecting the terahertz wave emitted from the generation means to a measurement object, by being irradiated with a second laser beam (LB2); reflection means (121) reflecting and emitting incident light; movement means (124, 221) moving the reflection means to an optical axis direction of the incident light; adjustment means (120, 220) adjusting an optical path length difference between an optical path length of the first laser beam and an optical path length of the second laser beam by the movement of the reflection means; and deflection means (125, 230, 235) provided in the adjustment means, and directing a movement direction of an air moving according to the movement of the reflection means toward a predetermined direction in which a cooled object to be cooled can be cooled.

Description

  The present invention relates to a technical field of a terahertz wave measuring apparatus that analyzes characteristics of a measurement object using, for example, a terahertz wave.

  As a terahertz wave measuring apparatus, an apparatus using terahertz time-domain spectroscopy (Terahertz Time-Domain Spectroscopy) is known. The terahertz wave measuring apparatus analyzes the characteristics of the measurement object according to the following procedure. First, pump light (in other words, excitation light), which is one laser light obtained by branching ultrashort pulse laser light (for example, femtosecond pulse laser light), generates terahertz waves to which a bias voltage is applied. The element is irradiated. As a result, the terahertz wave generating element generates a terahertz wave. The terahertz wave generated by the terahertz wave generating element is irradiated to the measurement object. The terahertz wave irradiated to the measurement object is another laser light obtained by branching the ultrashort pulse laser light as reflected light or transmitted light from the measurement object, and is optically delayed with respect to the pump light. In other words, the terahertz wave detecting element irradiated with the probe light (in other words, excitation light) to which the (optical path length difference) is applied is irradiated. As a result, the terahertz wave detecting element detects a current signal corresponding to the intensity of the terahertz wave reflected or transmitted by the measurement object. The detected terahertz wave (that is, a terahertz wave in the time domain and a current signal) is Fourier-transformed to obtain a spectrum (that is, frequency response characteristics of amplitude and phase) of the terahertz wave. As a result, the characteristics of the measurement object are analyzed by analyzing the spectrum of the terahertz wave.

  By the way, if the terahertz wave generating element is used for a relatively long time, the current that flows in the gap portion between two conductive elements (for example, a dipole antenna) included in the terahertz wave generating element increases abruptly. A problem occurs (for example, see Patent Document 1). One cause of the occurrence of such a technical problem is, for example, an increase in carriers that are thermally excited in the terahertz wave generating element. In order to solve such a technical problem, Patent Document 1 discloses a terahertz wave generating element that employs a cooling mechanism that cools the terahertz wave generating element or a heat dissipation mechanism that promotes heat dissipation of the terahertz wave generating element. A technique for suppressing a rapid increase in current flowing in a gap between two conductive elements provided is disclosed.

  In addition, there is Patent Document 2 as a document related to the present invention.

JP 2004-022766 A JP 2007-172799 A

  However, the technique disclosed in Patent Document 1 requires a new physical structure such as a cooling mechanism or a heat dissipation mechanism. Therefore, a new technical problem that leads to an increase in the size and cost of the terahertz wave measuring apparatus arises.

  Examples of problems to be solved by the present invention include the above. It is an object of the present invention to provide a terahertz wave measuring device that makes it possible to promote cooling or heat dissipation of a generating element that generates a terahertz wave while suppressing an increase in size and cost of the terahertz wave measuring device. And

  A terahertz wave measuring apparatus that solves the above-described problems is a generation unit that generates a terahertz wave by irradiating a first laser beam, and a measurement object from the generation unit by irradiating a second laser beam. Detecting means for detecting the terahertz wave irradiated to the reflecting means, reflecting means for reflecting and emitting incident light, and moving means for moving the reflecting means in the optical axis direction of the incident light, the reflecting means And adjusting means for adjusting the optical path length difference between the optical path length of the first laser light and the optical path length of the second laser light, and the adjusting means, and according to the movement of the reflecting means Deflecting means for directing the moving direction of the moving air in a predetermined direction in which the object to be cooled can be cooled.

It is a block diagram which shows the structure of the terahertz wave measuring device which concerns on 1st Example. It is a perspective view which shows each structure of a terahertz wave generation element and a terahertz wave detection element. It is a side view which shows the structure of the optical delay device which concerns on 1st Example with the flow of the air at the time of operation | movement. It is a top view which shows the structure of the optical delay device based on 2nd Example. It is a side view which shows the structure of the optical delay device which concerns on 2nd Example. It is an expansion perspective view which shows the structure of the optical delay device based on 2nd Example with the flow of the air at the time of operation | movement. It is an expansion perspective view (the 1) which shows the modification of the optical delay device concerning a 2nd example. It is a side view which shows the some modification of the optical delay device which concerns on 2nd Example. It is an expansion perspective view (the 2) which shows the modification of the optical delay device based on 2nd Example. It is an expansion perspective view (the 3) which shows the modification of the optical delay device which concerns on 2nd Example.

  The terahertz wave measuring apparatus according to the present embodiment is configured to generate a terahertz wave by irradiating the first laser light and irradiate the second laser light to the measurement object from the generating means. Detecting means for detecting the terahertz wave irradiated to the reflecting means, reflecting means for reflecting and emitting incident light, and moving means for moving the reflecting means in the optical axis direction of the incident light, the reflecting means And adjusting means for adjusting the optical path length difference between the optical path length of the first laser light and the optical path length of the second laser light, and the adjusting means, and according to the movement of the reflecting means Deflecting means for directing the moving direction of the moving air in a predetermined direction in which the object to be cooled can be cooled.

  According to the terahertz wave measuring apparatus of the present embodiment, the terahertz wave irradiated to the measurement object is detected using the terahertz time domain spectroscopy by the operation of the generating unit, the detecting unit, and the adjusting unit. The detected terahertz wave is used for analyzing the characteristics of the measurement object. Note that an existing detection method may be used as the terahertz wave detection method itself using the terahertz time domain spectroscopy. An outline of a terahertz wave detection method using terahertz time domain spectroscopy will be briefly described below.

  Specifically, the generation unit generates a terahertz wave by irradiating the generation unit with the first laser light as excitation light (for example, pump light). The terahertz wave generated by the generating means is irradiated to the measurement object.

  The detection means detects the terahertz wave reflected by the measurement object or transmitted through the measurement object by irradiating the detection means with the second laser light as excitation light (for example, probe light).

  At this time, the adjusting means adjusts the optical path length difference between the optical path of the first laser beam and the optical path of the second laser beam. In other words, the adjusting means sets the optical path length difference between the optical path of the first laser light and the optical path of the second laser light to a desired value. The adjusting unit includes a reflecting unit that reflects and emits incident light, and a moving unit that moves the reflecting unit in the optical axis direction of the incident light, and adjusts the optical path length difference by moving the reflecting unit. Specifically, the optical path length of the light emitted from the reflecting means is changed by moving the reflecting means in the optical axis direction of the incident light. Therefore, if at least one of the optical path length of the first laser light and the optical path length of the second laser light is incident on the reflecting means, the optical path length difference can be suitably adjusted. Note that such adjustment of the optical path length difference is performed in order to suitably detect the waveform of the terahertz wave that appears on the order of sub-picoseconds.

  In the present embodiment, in particular, the adjusting means described above is provided with a deflecting means. The deflecting unit directs the moving direction of the air that moves in accordance with the movement of the reflecting unit in a predetermined direction in which the object to be cooled can be cooled. Specifically, the deflecting unit is provided as an additional structure or a groove of the reflecting unit or the moving unit in the adjusting unit, for example. The deflecting means moves together by the movement of the reflecting means in the adjusting means, and directs the movement of air in a predetermined direction. In other words, the deflecting unit uses the moving operation of the reflecting unit in the adjusting unit to generate cooling air for cooling the object to be cooled.

  According to the configuration described above, cooling can be performed without separately providing a cooling device for cooling the object to be cooled. Further, since cooling is performed according to the operation of the adjusting means, it is not necessary to perform control for cooling. Therefore, a cooling control circuit or the like is not necessary. Therefore, it is possible to promote cooling or heat dissipation of the object to be cooled while suppressing an increase in the size and cost of the terahertz wave measuring apparatus.

  In one aspect of the terahertz wave measuring apparatus according to the present embodiment, the wind guide is provided so as to at least partially cover the adjusting unit, and guides the air directed in the predetermined direction by the deflecting unit to the object to be cooled. Means.

  According to this aspect, since the air guiding means is provided so as to at least partially cover the adjusting means, the air directed in the predetermined direction by the deflecting means can be more suitably guided to the cooled object. it can. Therefore, it is possible to further improve the cooling effect.

  In another aspect of the terahertz wave measuring apparatus according to this embodiment, the moving means is a rotary type or a direct acting type.

  According to this aspect, for example, the moving means is configured as a rotatable turntable, and the plurality of reflecting means are provided on the turntable. Thus, when the moving means is configured as a rotary type, the adjustment of the optical path length difference is executed by the rotating operation of the moving means. Then, the deflecting unit directs the moving air in a predetermined direction in accordance with the rotation operation of the moving unit.

  Alternatively, the moving means is configured as a movable member that can move linearly on the feed screw mechanism, for example, and the reflecting means is provided on the movable member. In this way, when the moving means is configured as a direct acting type, the adjustment of the optical path length difference is executed by the direct acting operation of the moving means. Then, the deflecting means directs the air that moves according to the linear motion of the moving means in a predetermined direction.

  As described above, if the moving means is a rotary type or a direct-acting type, the optical path length difference can be suitably adjusted, and the air flow caused by the adjusting operation can be surely directed in a predetermined direction.

  In another aspect of the terahertz wave measuring apparatus according to the present embodiment, the reflecting means is a retroreflector.

  According to this aspect, the reflecting means is configured as a reflector having, for example, two reflecting surfaces that intersect at right angles to each other, and emits reflected light parallel to the incident light. According to the retroreflector, the optical path length of the incident light can be suitably adjusted. In addition, since the deflecting means can be provided by using the structure of the retroreflector, a cooling effect can be obtained with a relatively simple configuration.

  In another aspect of the terahertz wave measuring apparatus according to the present embodiment, the object to be cooled is at least one of the generating means, the means for generating the first laser light, and the means for generating the second laser light. .

  According to this aspect, at least one of the generating means, the means for generating the first laser light, and the means for generating the second laser light is cooled by the air directed in a predetermined direction by the deflecting means. Here, in particular, the generating means, the means for generating the first laser light, and the means for generating the second laser light are more likely to cause problems due to heat than other parts. Therefore, the malfunction of an apparatus can be suppressed effectively by improving a cooling effect.

  The operation and other gains of the terahertz wave measuring apparatus according to this embodiment will be described in more detail in the following examples.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<1: First embodiment>
First, the terahertz wave measuring apparatus 100 according to the first embodiment will be described with reference to FIGS. 1 to 3.

<1-1: Device configuration>
First, the configuration of the terahertz wave measuring apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the terahertz wave measuring apparatus 100 according to the first embodiment.

  In FIG. 1, a terahertz wave measuring apparatus 100 irradiates a measurement target with a terahertz wave THz, and transmits a terahertz wave THz transmitted through the measurement target or reflected from the measurement target (that is, the terahertz wave irradiated on the measurement target). Wave THz).

The terahertz wave THz is an electromagnetic wave belonging to a frequency region (that is, a terahertz region) around 1 terahertz (1 THz = 10 ¹² Hz). The terahertz region is a frequency region that combines light straightness and electromagnetic wave transparency. The terahertz region is a frequency region in which various substances have unique absorption spectra. Therefore, the terahertz wave measuring apparatus 100 can analyze the characteristics of the measurement object by analyzing the frequency spectrum of the terahertz wave THz applied to the measurement object.

  In order to acquire the frequency spectrum of the terahertz wave THz irradiated on the measurement object, the terahertz wave measuring apparatus 100 employs terahertz time-domain spectroscopy (Terahertz Time-Domain Spectroscopy). The terahertz time domain spectroscopy irradiates the measurement target with the terahertz wave THz and performs Fourier transform on the time waveform of the terahertz wave THz that has passed through the measurement target or reflected from the measurement target. This is a method for acquiring a spectrum (that is, amplitude and phase for each frequency).

  Here, since the period of the terahertz wave THz is a period on the order of subpicoseconds, it is technically difficult to directly detect the time waveform of the terahertz wave THz. Therefore, the terahertz wave measuring apparatus 100 indirectly detects the time waveform of the terahertz wave THz by employing a pump-probe method based on time delay scanning.

  As shown in FIG. 1, a terahertz wave measuring apparatus 100 that employs such a terahertz time domain spectroscopy method and a pump-probe method includes a pulse laser device 101, a terahertz wave generating element 110, a beam splitter 161, and a reflecting mirror. 162, reflecting mirror 163, optical delay device 120, terahertz wave detection element 130, bias voltage generation unit 141, measurement interval signal generation unit 142, terahertz wave generation control unit 143, and IV (current − A voltage) conversion unit 144 and an arithmetic processing unit 150 are provided.

  The pulse laser device 101 generates pulse laser light LB in the sub-picosecond order or femtosecond order having light intensity corresponding to the drive current input to the pulse laser device 101. The pulse laser beam LB generated by the pulse laser device 101 is incident on the beam splitter 161 via a light guide (not shown) (for example, an optical fiber).

  The beam splitter 161 splits the pulsed laser light LB into pump light LB1 which is a specific example of “first laser light” and probe light LB2 which is a specific example of “second laser light”. The pump light LB1 is incident on the terahertz wave generating element 110 through a light guide path (not shown). On the other hand, the probe light LB2 enters the optical delay device 120 via a light guide path and a reflecting mirror 162 (not shown).

  The optical delay device 120 is a specific example of “adjustment means”, and adjusts the difference (that is, the optical path length difference) between the optical path length of the pump light LB1 and the optical path length of the probe light LB2. Specifically, the optical delay device 120 adjusts the optical path length between the optical path length of the pump light LB1 and the optical path length of the probe light LB2 by adjusting the optical path length of the probe light LB2. The timing at which the pump light LB1 enters the terahertz wave generation element 110 (or from the terahertz wave generation element 110) is adjusted by adjusting the optical path length difference between the optical path length of the pump light LB1 and the optical path length of the probe light LB2. The relative shift amount between the timing at which the outgoing terahertz wave THz enters the terahertz detection element 130) and the timing at which the probe light LB2 enters the terahertz wave detection element 130 can be adjusted. For example, when the optical path of the probe light LB2 is increased by 0.3 millimeters (however, the optical path length in the air) by the optical delay device 120, the timing at which the probe light LB2 enters the terahertz wave detection element 130 is delayed by 1 picosecond. Become. In this case, the timing at which the terahertz wave detecting element 130 detects the terahertz wave THz is delayed by 1 picosecond. Considering that the terahertz wave THz having the same waveform repeatedly enters the terahertz wave detecting element 130 at intervals of about several tens of MHz, the timing at which the terahertz wave detecting element 130 detects the terahertz wave THz is gradually shifted. Thus, the terahertz detection element 130 can indirectly detect the time waveform of the terahertz wave THz.

  However, the optical delay device 120 adjusts the optical path length of the pump light LB1 in addition to or in place of the optical path length of the probe light LB2, so that the optical path length between the optical path length of the pump light LB1 and the optical path length of the probe light LB2 is adjusted. The optical path length difference may be adjusted. In this case, the optical delay device 120 is preferably arranged on the optical path of the pump light LB1 between the beam splitter 161 and the terahertz wave generating element 110.

  In order to adjust the optical path length of the probe light LB2, the optical delay device 120 includes a retroreflecting mirror 121, a feed screw mechanism 122, and a motor 123.

  The retroreflecting mirror 121 is a specific example of “reflecting means”, and retroreflects the probe light LB2 incident on the retroreflecting mirror 121. That is, the retroreflective mirror 121 reflects the probe light LB2 incident on the retroreflective mirror 121 in a direction parallel to the incident direction of the probe light LB2. In the first embodiment, the retroreflecting mirror 121 includes a first reflecting surface 121a and a second reflecting surface 121b that intersect at an angle of 90 degrees. The first reflecting surface 121a reflects the probe light LB2 incident on the retroreflecting mirror 121 toward the second reflecting surface 121b. The second reflecting surface 121b reflects the probe light LB2 incident on the second reflecting surface 121b from the first reflecting surface 121a toward the outside of the retroreflecting mirror 120 (for example, the reflecting mirror 163).

  The retroreflective mirror 121 is provided on a movable member having a feed groove that fits into a feed screw mechanism 122 which is a specific example of “moving means”. As a result, the retroreflecting mirror 121 adjusts the optical path of the probe light LB2 (specifically, the optical path of the probe light LB2 when it enters the retroreflecting light 121 in accordance with the rotation of the feed screw mechanism 122 driven by the motor 123). Then, it moves along the vertical direction in FIG. By the movement of the retroreflecting mirror 121, the optical path length of the probe light LB2 is adjusted.

  The retroreflecting mirror 121 is moved under the control of the arithmetic processing unit 150. That is, the arithmetic processing unit 150 controls the operation of the motor 123 by outputting a control signal designating the drive amount of the motor 123 to the motor 123.

  The probe light LB2 emitted from the optical delay device 120 enters the terahertz wave detection element 130 via a light guide path and a reflecting mirror 163 (not shown).

  Here, the terahertz wave generating element 110 irradiated with the pump light LB1 and the terahertz detecting element 130 irradiated with the probe light LB2 will be described in more detail with reference to FIG. FIG. 2 is a perspective view showing the configuration of each of the terahertz wave generating element 110 and the terahertz wave detecting element 130. The configurations of the terahertz wave generation element 110 and the terahertz wave detection element 130 illustrated in FIG. 2 are merely examples, and a photoconductive antenna or a photoconductive switch having a configuration different from the configuration illustrated in FIG. The terahertz wave detecting element 130 may be used.

  As shown in FIG. 2A, the terahertz wave generating element 110 includes a substrate 111, an antenna (in other words, a transmission line) 112, and an antenna (in other words, a transmission line) 113.

  The substrate 111 is a semiconductor substrate such as a GaAs (Gallium Arsenide) substrate. Each of the antenna 112 and the antenna 113 is a monopole antenna having a shape extending in the longitudinal direction. The antenna 112 and the antenna 113 are arranged on the substrate 111 so as to be parallel in the short direction. A gap (that is, a gap) 114 of about several micrometers is secured between the antenna 112 and the antenna 113. Therefore, the antenna 112 and the antenna 113 as a whole constitute a dipole antenna.

  A bias voltage output from the bias voltage generation unit 141 is applied to the gap 114 via the antenna 112, the antenna 113, and the terahertz wave generation control unit 143. When the pump beam LB1 is irradiated to the gap 114 in a state where an effective bias voltage (for example, a bias voltage other than 0 V) is applied to the gap 114, the terahertz wave generation element 110 receives carriers by photoexcitation by the pump beam LB1. Occur. As a result, the terahertz wave generating element 110 generates a pulse-shaped current signal in the order of subpicoseconds or in the order of femtoseconds corresponding to the generated carrier. As a result, the terahertz wave generation element 110 generates a terahertz wave THz resulting from the pulsed current signal.

  As shown in FIG. 2B, the terahertz wave detecting element 130 also has the same configuration as the terahertz wave generating element 110. That is, the terahertz wave detecting element 130 includes a substrate 131, an antenna (in other words, a transmission line) 132, and an antenna (in other words, a transmission line) 133. The substrate 131, the antenna 132, and the antenna 133 have the same configuration as the substrate 111, the antenna 112, and the antenna 113, respectively.

  When the probe light LB2 is irradiated to the gap 134, carriers are generated in the terahertz detection element 130 by light excitation by the probe light LB2. When the terahertz detection element 130 is irradiated with the terahertz wave THz while the probe beam LB2 is irradiated on the gap 134, a current signal having a signal intensity corresponding to the light intensity of the terahertz wave THz is generated in the gap 134. . The current signal is output to the IV conversion unit 144 via the antenna 132 and the antenna 133.

  In FIG. 1 again, the terahertz wave THz emitted from the terahertz wave generating element 110 is irradiated onto the measurement object via an optical system (not shown) (for example, a lens). The terahertz wave THz applied to the measurement object is incident on the terahertz wave detection element 130 through a not-shown optical system (for example, a lens) as reflected light or transmitted light from the measurement object. As a result, the terahertz wave detection element 130 outputs a current signal having a signal intensity corresponding to the light intensity of the terahertz wave THz.

  The current signal output from the terahertz wave detection element 130 is converted into a voltage signal by the IV conversion unit 144. Thereafter, the arithmetic processing unit 150 performs synchronous detection on the voltage signal using the bias voltage as a reference signal. As a result, the arithmetic processing unit 150 detects a sample value of the terahertz wave THz. Thereafter, the same operation is repeated while appropriately adjusting the optical path length difference between the optical path length of the pump light LB1 and the optical path length of the probe light LB2, so that the arithmetic processing unit 150 detects the time waveform of the terahertz waveform. be able to. In addition, the arithmetic processing unit 150 may acquire a frequency spectrum (that is, an amplitude and a phase for each frequency) of the terahertz wave by performing a Fourier transform on the detected time waveform of the terahertz waveform. Furthermore, the arithmetic processing unit 150 may analyze the characteristics of the measurement object by analyzing the frequency spectrum of the terahertz wave.

  In the above description, the bias voltage generation unit 141, the measurement interval signal generation unit 142, and the terahertz wave generation control unit 143 are configured as configuration requirements (for example, hardware circuits) that are independent from the arithmetic processing unit 150 that is a CPU. ing. However, the bias voltage generation unit 141, the measurement interval signal generation unit 142, and the terahertz wave generation control unit 143 may be logical processing blocks realized by a computer program inside the arithmetic processing unit 150 that is a CPU.

  Here, if the terahertz wave generating element 110 continues to emit the terahertz wave THz for a long time, a technical problem that the current flowing through the gap 114 of the terahertz wave generating element 110 becomes excessively or rapidly increased occurs. . One of the causes that the current flowing through the gap 114 becomes excessively or rapidly increased is an increase in carriers that are thermally excited in the terahertz wave generating element 110. Therefore, in the first embodiment, the terahertz wave generation control unit 143 generates cooling air using the operation of the optical delay device 120 in order to suppress heat generation in the terahertz wave generation element 110.

<1-2: Specific Configuration and Operation of Optical Delay Device>
Hereinafter, a specific configuration and operation of the optical delay device 120 for cooling the terahertz wave generating element 110 will be described with reference to FIG. FIG. 3 is a side view showing the configuration of the optical delay device according to the first embodiment together with the air flow during operation.

  As shown in FIG. 3A, the optical delay device 120 is configured such that a movable member 124 is movable in the left-right direction in the drawing by a feed screw mechanism 122. A retroreflecting mirror 121 is provided on the movable member 124, and an additional structure 125, which is a specific example of “deflecting means”, is further provided on the retroreflecting mirror.

  Here, when the retroreflecting mirror 121 is moved in the direction in which the light enters, the additional structure 125 provided on the retroreflecting mirror 121 directs the air flow upward in the drawing. Specifically, as shown in the figure, air moves along the slope on the right side of the additional structure 125 in the figure, so that an upward air flow occurs.

  As shown in FIG. 3B, when the retroreflecting mirror 121 is moved in the direction opposite to the direction in which the light enters, similarly, the additional structure 125 provided on the retroreflecting mirror 121 Air flow is directed upward in the figure. Specifically, as shown in the drawing, since air moves along the slope on the left side of the additional structure 125 in the drawing, an upward air flow occurs.

  As described above, in the optical delay device 120 according to the first embodiment, an upward air flow is generated according to the linear movement of the retroreflecting mirror 121. That is, the movement of the retroreflecting mirror 121 can be used to generate an air flow in a predetermined direction. Therefore, if the air flow thus generated is guided to the terahertz generating element 110 to be cooled, cooling can be performed without providing a cooling device such as a cooling fan. Further, since cooling is performed according to the operation of the optical delay device 120, it is not necessary to perform control for cooling. Therefore, a cooling control circuit or the like is not necessary. Therefore, cooling or heat dissipation of the terahertz wave generating element 110 can be promoted while suppressing an increase in the size and cost of the terahertz wave measuring apparatus 100.

  Here, the case where the terahertz wave generating element is a specific example of the “object to be cooled” has been described. However, for example, other parts such as the pulse laser device 101 and the terahertz wave detecting element 130 may be cooled. Good.

  Moreover, the shape of the additional structure 125 mentioned above is an example, and as long as it has the effect of directing the flow of air in a predetermined direction, it may be a different shape. Further, instead of providing an additional structure, the shapes of the retroreflecting mirror 121 and the movable member 124 may be changed to function as a specific example of “deflecting means”.

<2: Second embodiment>
Next, the terahertz wave measuring apparatus 200 according to the second embodiment will be described with reference to FIGS. 4 to 10. The terahertz wave measurement apparatus 200 according to the second embodiment is different from the terahertz wave measurement apparatus 100 according to the first embodiment in that the configuration of the optical delay device 220 is different. The other components of the terahertz wave measuring apparatus 200 of the second embodiment are the same as the other components of the terahertz wave measuring apparatus 100 of the first embodiment. Therefore, in the following, portions different from the above-described first embodiment will be described in detail, and description of overlapping portions will be omitted as appropriate.

<2-1: Device configuration>
First, the overall configuration of the optical delay device according to the second embodiment will be described with reference to FIGS. FIG. 4 is a top view showing the configuration of the optical delay device according to the second embodiment. FIG. 5 is a side view showing the configuration of the optical delay device according to the second embodiment.

  4 and 5, the optical delay device 220 according to the second embodiment includes a rotating substrate 221 that can rotate around the shaft 225 by the operation of the motor 224 and a plurality of (four in FIG. 4) retroreflections. And a mirror 121. The plurality of retroreflecting mirrors 121 are arranged at equal intervals on a circle C centered on the rotation axis of the rotating substrate 221. Accordingly, each of the plurality of retroreflecting mirrors 121 circulates on the circle C as the rotating substrate 221 rotates.

  In addition, the optical delay device 220 according to the second embodiment is particularly covered with a flow path portion 250 which is a specific example of “air guiding means”. The function of the flow path part 250 will be described in detail later.

  During the operation of the optical delay device 220, the probe light LB2 is incident from the beam splitter 161 via the reflection mirror 162. The incident probe light LB <b> 2 is reflected by the retroreflecting mirror 121 existing on the optical path and is emitted to the terahertz wave detecting element 130 through the reflecting mirror 163. At this time, since the optical path to the retroreflecting mirror 121 can be changed by the rotation operation of the rotating substrate 221, the optical path length difference between the pump light LB2 and the probe light LB1 can be suitably adjusted.

<2-2: Specific Configuration and Operation of Optical Delay Device>
Next, a specific configuration and operation of the optical delay device 220 for cooling the terahertz wave generating element 110 will be described with reference to FIGS. FIG. 6 is an enlarged perspective view showing the configuration of the optical delay device according to the second embodiment together with the air flow during operation. FIGS. 7, 9 and 10 are enlarged perspective views showing modifications of the optical delay device according to the second embodiment. FIG. 8 shows a plurality of modifications of the optical delay device according to the second embodiment. FIG.

  As shown in FIG. 6, when the retroreflecting mirror 121 is moved in the direction in which light enters, the retroreflecting mirror 121 itself in which the two reflecting mirrors are arranged at an angle of 90 degrees causes the air flow to flow. Directed upward in the figure. That is, here, the retroreflecting mirror 121 functions as a specific example of the “deflecting unit”. Therefore, it is not necessary to arrange a new member, and the complexity of the device configuration and the increase in cost can be suppressed.

  As shown in FIG. 7, an additional structure 230, which is a specific example of “deflecting means”, may be provided on the back side of the reflecting surface of the retroreflecting mirror 121. According to such a configuration, even when the retroreflective member 121 is moved in a direction opposite to the direction in which light enters, the air flow is directed upward in the drawing. Specifically, as shown in the drawing, since air moves along the slope of the additional structure 230, an upward air flow is generated. With this configuration, the air flow can be directed upward regardless of the rotation direction of the rotating substrate 221.

  As shown in FIG. 8, the additional structure 230 may be provided on the retroreflecting mirror 121. Specifically, according to the configuration illustrated in FIG. 8A, an air flow along the slope of the additional structure 230 is generated by the rotation operation of the rotating substrate 221. Further, according to the configuration shown in FIG. 8B, since the slope of the additional structure 230 is curved, the air flow can be directed more effectively than in the case of FIG. Further, according to the configuration shown in FIG. 8C, the air coming out from the upper part of the retroreflecting mirror 121 is also directed upward. Therefore, the upward air flow can be generated efficiently.

  As shown in FIG. 9, the shape of the additional structure 230 may not have a slope. The additional structure 230 shown in FIG. 9 has a function of adjusting and strengthening the flow of air directed upward by the shape of the retroreflector 121.

  As shown in FIG. 10, a groove 235 may be formed on the rotating substrate 221 in addition to or instead of the additional structure 230. Also in this case, as in the case of providing the additional structure 230 described above, an upward air flow can be generated by the rotation operation of the rotating substrate 221.

  As described above, the air that flows upward is guided to the terahertz wave generating element 110 by the flow path portion 250 described above. In other words, the flow path section 250 has a function of more preferably guiding the upward air flow generated by the optical delay device 120 to the cooled object. Therefore, according to the terahertz wave measuring apparatus according to the second embodiment, it is possible to cool the object to be cooled very suitably. In addition, the flow path part 250 is applicable also to the terahertz wave measuring apparatus which concerns on 1st Example mentioned above.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and terahertz wave measurement with such a change is possible. The apparatus is also included in the technical scope of the present invention.

100, 200 Terahertz wave measuring device 101 Pulse laser device 110 Terahertz wave generating element 120, 220 Optical delay device 121 Retroreflector 122 Feed screw mechanism 123 Motor 124 Movable member 125, 230 Additional structure 221 Rotating substrate 224 Motor 225 Shaft 235 Groove 250 Channel part 130 Terahertz wave detection element 141 Bias voltage generation part 142 Measurement section signal generation part 143 Terahertz wave generation control part 144 IV conversion part 150 Arithmetic processing part 161 Beam splitter 162,163 Reflection mirror LB Pulse laser light LB1 Pump Light LB2 Probe light THz Terahertz wave

Claims (5)

Generating means for generating a terahertz wave by being irradiated with the first laser beam;
Detecting means for detecting the terahertz wave irradiated to the measurement object from the generating means by being irradiated with the second laser beam;
Reflecting means for reflecting and emitting incident light, and moving means for moving the reflecting means in the optical axis direction of the incident light, and the optical path length of the first laser light and the second by moving the reflecting means Adjusting means for adjusting the optical path length difference between the optical path length of the laser beam;
And a deflecting unit which is provided in the adjusting unit and directs the moving direction of the air moving according to the movement of the reflecting unit in a predetermined direction in which the object to be cooled can be cooled. Terahertz wave measuring device.   2. The air guide unit according to claim 1, further comprising an air guide unit that is provided so as to at least partially cover the adjusting unit and guides the air directed in the predetermined direction by the deflecting unit to the object to be cooled. Terahertz wave measuring device.   The terahertz wave measuring apparatus according to claim 1, wherein the moving unit is a rotary type or a direct acting type.   The terahertz wave measuring apparatus according to claim 1, wherein the reflecting means is a retroreflector.   5. The cooling object according to claim 1, wherein the object to be cooled is at least one of the generating unit, the first laser beam generating unit, and the second laser beam generating unit. The terahertz wave measuring device described in 1.

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