JPWO2011118398A1 - Terahertz light receiving and emitting module - Google Patents

Abstract

The antenna element (14) of the module (11) has an antenna pattern formed on the front surface, and abuts against the flat surface of the hemispherical lens (13) on the back surface. The mount element (15) is provided with an opening (15C), a rectangular recess (15B), and a circular recess (15A), and the opening (15C) exposes the antenna pattern. The rectangular recess (15B) is provided with an opening (15C) on the bottom surface of the recess, and abuts the side surface of the antenna element (14) on the side surface of the recess to position the antenna element (14). The circular concave portion (15A) is provided with a rectangular concave portion (15B) on the bottom surface of the concave portion, and contacts the spherical surface of the hemispherical lens (13) on the side surface of the concave portion, thereby positioning the lens (13). The fixed cover (12) contacts the spherical surface of the hemispherical lens (13) and holds the antenna element (14) and the lens (13) between the mount element (15).

Description

  The present invention relates to a terahertz light receiving and emitting module used as a terahertz light emitter or detector.

  A terahertz light receiving and emitting module is used as a terahertz light emitter or detector. The terahertz light receiving and emitting module includes a photoconductive antenna element, a hemispherical lens, and a module housing (see, for example, Patent Documents 1 to 3).

  The photoconductive antenna element is formed by forming an antenna pattern of a predetermined shape such as a dipole antenna or a bow tie antenna on a GaAs substrate provided with a low temperature growth GaAs film. An antenna pattern of a photoconductive antenna element generally has an electrode gap portion where electrodes are opposed to each other with a minute gap, and pulse pulse laser light is irradiated to the electrode gap portion in a state where a bias voltage is applied. Thus, photoexcited carriers generated instantaneously are accelerated by a bias electric field and emitted as terahertz light. In addition, when detecting terahertz light, a pulsed laser beam for excitation is irradiated onto the electrode gap portion in a state where the terahertz light is irradiated, so that a minute current corresponding to the electric field intensity by the terahertz light is generated in the electrode gap portion. The intensity of the terahertz light can be detected based on this minute current. The hemispherical lens has a flat surface and a spherical surface, and is provided so that the flat surface is in close contact with the photoconductive antenna element, suppressing reflection at the interface with the photoconductive antenna element and free from the photoconductive antenna element. Terahertz light is radiated into space, or terahertz light is collected from free space onto a photoconductive antenna element.

When the photoconductive antenna element emits terahertz light, it emits terahertz light using the electrode gap portion as a point light source. When the point light source is deviated from the optical axis of the hemispherical lens, the wavefronts of the terahertz light propagating in the hemispherical lens are not matched, and the radiation efficiency and band characteristics of the terahertz light to free space are deteriorated. The same applies to the case where terahertz light is detected. When the electrode gap is displaced from the optical axis of the hemispherical lens, the condensing efficiency and detection efficiency of the terahertz light are reduced.
For this reason, in the terahertz light receiving and emitting module, it is necessary to position the photoconductive antenna element and the hemispherical lens very precisely in units of micrometers, and to place the point light source of the photoconductive antenna element on the optical axis of the hemispherical lens. Yes.

Therefore, conventionally, after the photoconductive antenna element and the hemispherical lens are fixed to the module housing by independent holding members, the positioning accuracy of the photoconductive antenna element and the hemispherical lens is adjusted, thereby improving the positioning accuracy. It was higher.
For example, Patent Document 1 employs a configuration in which a holding member that independently holds a hemispherical lens and a photoconductive antenna element is used, and both are fixed to the module housing by a plurality of members.
In Patent Document 2, a photoconductive antenna element is fixed to a wiring board, a hemispherical lens is fitted into a module housing provided with a buffer member, and the wiring board on which the photoconductive antenna element is attached is attached to the flat surface of the hemispherical lens. The structure which is pressed and fixed from the side is adopted. The module housing has a recess for positioning the wiring board.
In Patent Document 3, a hemispherical lens is fixed to a module housing by a holding member made of plastic or rubber, and a photoconductive antenna element is fitted into an aperture having a positioning structure provided in the module housing. The structure fixed by is adopted.

JP 2004-207288 A JP 2008-244620 A JP 2008-283552 A

  In the conventional case where positioning of the hemispherical lens and the photoconductive antenna element is performed by fixing the hemispherical lens and the photoconductive antenna element to the module housing with independent holding members, a plurality of members having complicated shapes processed with extremely high accuracy are required. In addition, there is a problem that it is necessary to perform extremely precise and advanced position adjustment work after assembly, and the manufacturing cost of the module becomes expensive.

  For example, in the configuration of Patent Document 1, in order to make the center positions of the hemispherical lens and the photoconductive antenna element coincide with each other, it is necessary to manufacture each of the plurality of members with ideal dimensional accuracy. It is difficult to align all members with a high dimensional accuracy. In addition, paragraph 0067 of the same document describes that the recess for positioning the element holding member is slightly larger than the outer shape of the element holding member to allow a margin, but such a margin is given. Then, precise positioning becomes difficult, and eventually it becomes necessary to perform position adjustment work by an extremely skilled worker.

  Further, for example, in the configuration of Patent Document 2, it is necessary to fix the photoconductive antenna element to the wiring board, but there is no mention of a method for positioning the photoconductive antenna element with respect to the wiring board.

  For example, in the configuration of Patent Document 3, a lens is fitted into an opening provided in a module housing, and a photoconductive antenna element is fitted into an opening provided on the opposite side of the lens. Since the opening portion has a depth substantially equal to the thickness of the module housing, it cannot be physically assembled unless the opening size has a margin. Therefore, as described in paragraph 0044 of the same document, even if the position of the photoconductive antenna element can be regulated to some extent by the wall surface of the opening, the positioning accuracy is not sufficient, and the hemispherical lens It is difficult to sufficiently increase the matching accuracy between the optical axis and the point light source of the photoconductive antenna element.

  Furthermore, in the case of a dipole type antenna pattern that is used most frequently, it is necessary to focus the pulse laser beam on a small spot diameter of 10 μm or less and irradiate the electrode gap portion. Need to use. The single lens type objective lens has a high magnification, but generally requires a working distance of about 1.3 mm, and needs to be placed very close to the photoconductive antenna element. However, in the above conventional configuration, it is difficult to keep the objective lens close to the photoconductive antenna element because the member for holding the photoconductive antenna element becomes an obstacle, and there is a problem that the single lens type objective lens cannot be used. . A double-lens type high-magnification objective lens has a long working distance, so it can be arranged farther from the photoconductive antenna element than a single-lens objective lens. It is desirable to avoid using the terahertz light that is generated by expanding the pulse width because the band is narrowed.

  The present invention has been made in view of the above circumstances, has a simple structure, can achieve sufficient positioning accuracy without performing position adjustment work, and a single-lens objective lens for a photoconductive antenna element. An object of the present invention is to provide a terahertz light receiving and emitting module that can be brought close to each other.

  The invention according to claim 1 is a terahertz light receiving and emitting module including a hemispherical lens, a photoconductive antenna element, and a module housing, and includes a mount element and a fixed cover. The hemispherical lens is made of a material that transmits terahertz light, and is provided with a flat surface perpendicular to the optical axis and a spherical surface having a center on the optical axis. The photoconductive antenna element has a flat plate shape, an antenna pattern is formed on the front main surface, and the back main surface contacts the flat surface of the hemispherical lens so that the point light source position of the antenna pattern is on the optical axis. The module housing holds a photoconductive antenna element and a mount element equipped with a hemispherical lens. The mount element has an opening, an element holding recess, and a lens holding recess along the optical axis. The opening exposes the point light source position of the antenna pattern. The element holding recess is provided with an opening on the bottom surface of the recess and abuts on the main surface of the photoconductive antenna element. Regulating displacement in any direction. The lens holding concave portion is provided with an element holding concave portion on the bottom surface of the concave portion, and abuts against the spherical surface of the hemispherical lens on the side surface of the concave portion to restrict the hemispherical lens from being displaced in a direction perpendicular to the optical axis. . The fixed cover is in contact with the spherical surface of the hemispherical lens and holds the photoconductive antenna element and the hemispherical lens between the mounting element.

In this configuration, the hemispherical lens can be positioned in the vertical direction of the optical axis and the photoconductive antenna element can be positioned in the vertical direction of the optical axis only by the mount element. The positioning accuracy of both is determined according to the shape accuracy of the recess. That is, the accuracy of matching the optical axis of the hemispherical lens with the point light source of the photoconductive antenna element can be increased only by the shape accuracy of the mount element, hemispherical lens, and photoconductive antenna element.
In addition, the photoconductive antenna element and the hemispherical lens can be fixed in the direction along the optical axis by holding the mount element and the fixed cover. The antenna element and the hemispherical lens can be fixed, and the number of work steps for assembly can be reduced. In addition, the depth of the concave portion for holding the element can be made as shallow as the thickness of the photoconductive antenna element, thereby allowing the photoconductive antenna to be provided in the concave portion for holding the element without giving a margin to the opening size of the concave portion for holding the element. The element can be assembled. This eliminates the need to adjust the position of the photoconductive antenna element, increases the matching accuracy between the optical axis of the hemispherical lens and the point light source of the photoconductive antenna element without requiring special techniques for assembly, and reduces the manufacturing cost. Can be reduced.

In the mount element according to the second aspect of the present invention, it is preferable that the recess depth of the element holding recess is shallower than the thickness of the photoconductive antenna element.
With this configuration, the photoconductive antenna element and the hemispherical lens can be securely adhered.

In the mount element according to the third aspect of the present invention, it is preferable that the thickness dimension of the opening is 1 mm or less.
In this configuration, it is easy to bring the single lens objective lens close to the photoconductive antenna element up to a distance (for example, 1.3 mm) at which sufficient focusing can be performed with the single lens objective lens, and the single lens objective lens is used. Thus, it becomes possible to focus the pulse laser beam on a small spot diameter of 10 μm or less.

  The terahertz light receiving and emitting module of the invention according to claim 4 is preferably provided with a buffer member in a gap surrounded by the mount element, the photoconductive antenna element, and the hemispherical lens.

The buffer member of the invention according to claim 5 is preferably an elastic member.
When the area of the flat surface of the hemispherical lens is particularly large compared to the area of the photoconductive antenna element, the gap surrounded by the mount element, photoconductive antenna element, and hemispherical lens becomes large, and photoconductive during assembly. It may be difficult to maintain the parallelism of the hemispherical lens with respect to the antenna element. Therefore, by providing a buffer material in the gap, it becomes easy to maintain the parallelism of the hemispherical lens with respect to the photoconductive antenna element during assembly, and the hemispherical lens can be held more stably.

It is preferable that the fixed cover of the invention according to claim 6 has an opening having an opening diameter smaller than the diameter of the hemispherical lens.
With this configuration, the fixed cover can be easily assembled to the hemispherical lens, and the photoconductive antenna element and the hemispherical lens can be securely adhered to each other.

The fixing cover of the invention according to claim 7 is preferably made of resin.
In this configuration, since the fixed cover is made of resin and has a certain elasticity, it is possible to prevent the photoconductive antenna element from being damaged due to excessive stress during assembly. Furthermore, since it can be easily manufactured by an injection molding method or the like if it is made of resin, the cost can be reduced by mass production.

A module housing according to an eighth aspect of the present invention includes an attachment part for attaching the mount element, an opening for exposing the antenna pattern, and a connector part for electrically connecting the antenna pattern to an external circuit. It is preferable that the connector portion and the antenna pattern are connected via a wiring wire passing through the opening and the opening of the mount element.
With this configuration, wiring to the antenna pattern can be performed after the hemispherical lens and the photoconductive antenna element are attached to the mount element. Then, it is possible to prevent the assembling work and the assembling structure from becoming complicated due to restrictions on the wiring structure.

According to the present invention, the positioning of the hemispherical lens in the vertical direction of the optical axis and the positioning of the photoconductive antenna element in the vertical direction of the optical axis are performed only by the element holding recess and the lens holding recess provided coaxially on the mount element. By doing so, the matching accuracy between the optical axis and the point light source can be increased.
In addition, by fixing the photoconductive antenna element and the hemispherical lens in the direction along the optical axis by holding the mount element and the fixed cover, the photoconductive antenna element can be obtained only by fixing the mount element and the fixed cover. And hemispherical lens can be fixed, and the number of work steps for assembly can be reduced. In addition, the depth of the concave portion for holding the element can be made as shallow as the thickness of the photoconductive antenna element, thereby allowing the photoconductive antenna to be provided in the concave portion for holding the element without giving a margin to the opening size of the concave portion for holding the element. The element can be reliably positioned and assembled. This eliminates the need to adjust the position of the photoconductive antenna element, increases the matching accuracy between the optical axis of the hemispherical lens and the point light source of the photoconductive antenna element without requiring special techniques for assembly, and reduces the manufacturing cost. Can be reduced.

It is an assembly view of the terahertz light receiving and emitting module according to the first embodiment. It is a figure explaining the structure of the terahertz light receiving / emitting module shown in FIG. It is a figure explaining the example of a drive of the terahertz light receiving / emitting module shown in FIG. It is an assembly drawing of the terahertz light receiving and emitting module according to the second embodiment. It is a figure explaining the structure of the terahertz light receiving / emitting module shown in FIG.

<< First Embodiment >>
Hereinafter, a configuration example of the terahertz light receiving and emitting module according to the first embodiment of the present invention will be described. FIG. 1 is a schematic assembly diagram of a terahertz light receiving and emitting module 11 according to the present embodiment. 2A is a schematic front view of the terahertz light receiving / emitting module 11, FIG. 2B is a schematic rear view of the terahertz light receiving / emitting module 11, and FIG. 2C is a terahertz light receiving / emitting light. FIG. 3 is a schematic cross-sectional view of the module 11 taken along the line AA ′ in FIG. For convenience of explanation, FIGS. 1 and 2 display the photoconductive antenna element 14 and the mount element 15 of the terahertz light receiving and emitting module 11 rotated by 90 degrees.

  The terahertz light receiving / emitting module 11 includes a fixed cover 12, a hemispherical lens 13, a photoconductive antenna element 14, a mount element 15, and a module housing 16.

  The module housing 16 has a box shape excluding the rear side wall surface, and is made of a metal that is easy to process such as aluminum and has little corrosiveness. The module housing 16 is provided with a circular opening in the center of the front, and a screw hole serving as a mounting portion for the mount element along the outer periphery of the circular opening. Further, an SMA connector 17 is provided on the side wall surface of the module housing 16. As shown in FIG. 2B, the SMA connector 17 is connected to the positive electrode (+) of the antenna pattern 18 by a wiring wire 19A. The negative electrode (−) of the antenna pattern 18 is connected to the module housing 16 by the wiring wire 19B and grounded.

  The fixed cover 12 is formed of an annular resin plate, and a circular opening is provided at the center, and a screw hole is provided along the outer periphery of the circular opening. The circular opening has an opening diameter smaller than that of the hemispherical lens 13. The fixed cover 12 is assembled to the mount element 15 by a fixing screw, and when assembled to the mount element 15, the edge of the opening side surface contacts the spherical surface of the hemispherical lens 13 over the entire circumference. For this reason, the opening center axis of the fixed cover 12 passes through the center of the spherical surface of the hemispherical lens 13.

  Since the fixing cover 12 is made of resin and has elasticity, it can prevent the hemispherical lens 13 and the photoconductive antenna element 14 from being damaged due to excessive stress when the fixing screw is tightened. In addition, it can be mass-produced by an injection molding method and manufactured at a low cost.

  The hemispherical lens 13 is made of a material that has substantially the same refractive index as the constituent material of the photoconductive antenna element 14 (here, mainly GaAs) and transmits terahertz light, such as high-resistance silicon, and has a flat surface and a center of the flat surface. And a spherical surface having a center on a perpendicular line passing through. A perpendicular passing through the center of the flat surface becomes the optical axis of the hemispherical lens 13. Here, a so-called hemispherical lens in which the center of the spherical surface is located on a flat surface is used as the hemispherical lens 13. As the hemispherical lens 13, a so-called super hemispherical lens in which the center of the spherical surface is located inside the hemispherical lens 13 may be used. In the super hemisphere lens, the directivity region of the irradiated terahertz light can be controlled in a beam shape. The hemispherical lens 13 is assembled to the mount element 15 so that the spherical surface faces the front side and the flat surface faces the back side.

The photoconductive antenna element 14 is a rectangular flat plate having a thickness of about 0.35 mm, the diagonal dimension of the flat plate is smaller than the diameter of the hemispherical lens 13, and the antenna pattern 18 is formed on the surface as shown in FIG. Prepare. The photoconductive antenna element 14 is assembled to the mount element 15 so that the back surface is in contact with the flat surface of the hemispherical lens 13.
FIG. 2B also shows a surface view of the photoconductive antenna element 14 alone. The photoconductive antenna element 14 is formed by forming a low-temperature grown GaAs film on the surface of a flat GaAs substrate and providing an antenna pattern 18 on the surface of the low-temperature grown GaAs film. The antenna pattern 18 includes a pair of antenna electrodes 18A and 18B. The antenna electrode 18A and the antenna electrode 18B are line-symmetric with each other, and center on an electrode gap portion 18C facing each other with a minute interval (generally about 5 μm). Have in the department. This electrode gap portion 18C is the point light source position described in the claims. The antenna electrodes 18A and 18B can be formed by a lithography method or the like generally used in the manufacture of semiconductors, and the external dimensional accuracy of the photoconductive antenna element 14 is extremely high by using a dicer for processing semiconductor chips. It can be obtained with high accuracy. Therefore, the substrate center of the photoconductive antenna element 14 and the electrode gap portion 18C of the antenna pattern 18 can be matched with an error of 1 μm or less.

  The mount element 15 is formed of a substantially annular resin plate, and a circular recess 15A is provided at the center of the surface, a rectangular recess 15B is provided at the center of the bottom of the recess of the circular recess 15A, and an opening 15C is provided at the bottom of the recess of the rectangular recess 15B. Is provided. Further, double screw holes are provided on the surface along the outer periphery of the circular recess 15A. The outer screw holes are used for assembling the mount element 15 to the module housing 16, and the inner screw holes are used for the fixing cover 12. Used for assembling.

  The circular recess 15A is a lens holding recess according to the claims. When the hemispherical lens 13 is assembled to the circular concave portion 15A, the spherical surface of the hemispherical lens 13 contacts the side surface of the concave portion over the entire circumference. The rectangular recess 15B is the element holding recess described in the claims, and is formed with a recess depth of about 0.3 mm. The center of the rectangular recess 15B is arranged so as to be coaxial with the center of the circular recess 15A. When the photoconductive antenna element 14 is assembled to the rectangular recess 15B, the surface of the photoconductive antenna element 14 contacts the bottom surface of the recess and the side surface of the photoconductive antenna element 14 contacts the side surface of the recess over the entire circumference. The opening 15 </ b> C has substantially the same shape as the antenna pattern 18 provided on the surface of the photoconductive antenna element 14, and at least the central portion of the antenna pattern 18 is exposed to the back side of the terahertz light receiving / emitting module 11.

  The photoconductive antenna element 14 is assembled by assembling the photoconductive antenna element 14, the hemispherical lens 13, and the fixed cover 12 on the surface side of the mount element 15 having such a shape and fixing the fixed cover 12 with a fixing screw. The hemispherical lens 13 is held between the fixed cover 12 and the mount element 15. Therefore, the photoconductive antenna element 14 and the hemispherical lens 13 can be fixed only by fixing the mount element 15 and the fixed cover 12, and the number of work steps for assembly can be reduced as compared with the conventional configuration.

  Since the center of the circular recess 15A and the center of the rectangular recess 15B are coaxially arranged, the center of the photoconductive antenna element 14 is placed on the optical axis of the hemispherical lens 13 passing through the center of the flat surface of the hemispherical lens 13. That is, the electrode gap portion 18C is located. Then, the concave side surface of the circular concave portion 15A contacts the spherical surface of the hemispherical lens 13 over the entire circumference, and the concave side surface of the rectangular concave portion 15B contacts the side surface of the photoconductive antenna element 14 over the entire circumference. The positional deviation of the photoconductive antenna element 14 in the direction perpendicular to the optical axis with respect to the mount element 15 is restricted, and the hemispherical lens 13 and the photoconductive antenna element according to the shape accuracy of the circular recess 15A and the rectangular recess 15B in the mount element 15 The positioning accuracy with respect to 14 is determined.

  In addition, since the recess depth of the rectangular recess 15B is shallower than the thickness of the photoconductive antenna element 14, the photoconductive antenna element 14 can be assembled to the rectangular recess 15B even if there is no allowance for the opening size of the rectangular recess 15B. Thus, the position adjustment work of the photoconductive antenna element 14 becomes unnecessary. In addition, the back surface of the photoconductive antenna element 14 protrudes from the rectangular recess 15 </ b> B, and the photoconductive antenna element 14 is completely adhered to the hemispherical lens 13. In addition, even if the photoconductive antenna element 14 and the hemispherical lens 13 are brought into contact with each other, the thickness of the element holding portion in the rectangular recess 15B is set to such a thickness that can realize a certain mechanical strength. Is possible.

Hereinafter, an example in which the terahertz light receiving and emitting module 11 is used as a terahertz light emitter will be described.
FIG. 3A is a schematic cross-sectional view of the terahertz light receiving and emitting module 11 in a state in which the single lens type objective lens 51 is brought close. FIG. 3B is a schematic diagram of the terahertz light receiving and emitting module 11 with the bias power supply 50 connected thereto.

  When the terahertz light receiving / emitting module 11 is used as a terahertz light emitter, the antenna pattern 18 is connected between the bias power supply 50 and the ground via the wiring wires 19A and 19B, and the antenna pattern is connected from the bias power supply 50 to the antenna pattern. A bias voltage (generally about 10 to 100 V) is applied to 18. Further, the single lens type objective lens 51 is brought close to the electrode gap part 18C, and the pulse laser beam L condensed by the single lens type objective lens 51 is irradiated to the electrode gap part 18C.

  As a result, photoexcited carriers instantaneously generated in the low-temperature grown GaAs film of the photoconductive antenna element 14 are accelerated by the bias electric field, and a current flows instantaneously in the electrode gap portion 18C. Then, terahertz light is generated by using the electrode gap portion 18C as a point light source by electric dipole radiation. The terahertz light is radiated into the substrate of the photoconductive antenna element 14 and is radiated from the hemispherical lens 13 to free space.

At this time, since the electrode gap portion 18C is arranged on the optical axis of the hemispherical lens 13, the wavefront of the terahertz light propagating in the hemispherical lens 13 is matched, and the radiation efficiency to free space and the band characteristics are improved. It will be good. The same applies to the case where terahertz light is detected. By arranging the electrode gap portion 18C on the optical axis of the hemispherical lens 13, the condensing efficiency and detection efficiency of the terahertz light are improved.
In addition, the circular opening of the module housing 16 has a larger opening diameter than the diameter of the single-lens objective lens 51, and the thickness dimension of the opening 15C of the mount element 15 is about 1 mm. The lens-type objective lens 51 can be brought close to the photoconductive antenna element 14 up to a distance (for example, about 1.3 mm) at which sufficient condensing can be performed.

<< Second Embodiment >>
Hereinafter, a configuration example of the terahertz light receiving and emitting module according to the second embodiment of the present invention will be described. FIG. 4 is a schematic assembly diagram of the terahertz light receiving and emitting module 21 according to the present embodiment. FIG. 5 is a cross-sectional view of the terahertz light receiving / emitting module 21. In addition, in the figure, the same code | symbol is attached | subjected to the structure similar to the structure shown in 1st Embodiment.

  The terahertz light receiving / emitting module 21 has a configuration in which a buffer material 24 is added to the configuration of the first embodiment. The buffer material 24 is an annular elastic member made of a vinyl film or the like, and has a rectangular opening. The buffer material 24 is assembled in the circular recess 15A of the mount element 15, and the photoconductive antenna element 14 is housed in the inner opening. By providing the buffer material 24, the space surrounded by the mount element 15, the photoconductive antenna element 14, and the hemispherical lens 13 can be filled with an elastic member. Then, it becomes easy to maintain the parallelism of the hemispherical lens 13 with respect to the photoconductive antenna element 14 during assembly, and the hemispherical lens 13 can be held more stably.

  As shown in each of the embodiments described above, by configuring the terahertz light receiving and emitting module of the present invention, no special technique is required at the time of assembly with a simple configuration, and the optical axis of the hemispherical lens and the photoconductive antenna The matching accuracy with the point light source of the element can be increased.

DESCRIPTION OF SYMBOLS 11, 21 ... Terahertz light receiving and emitting module 12 ... Fixed cover 13 ... Hemispherical lens 14 ... Photoconductive antenna element 15 ... Mount element 15A ... Circular recessed part 15B ... Rectangular recessed part 15C ... Opening part 16 ... Module housing 17 ... SMA connector 18 ... Antenna pattern 18A, 18B ... Antenna electrode 18C ... Electrode gap 19A, 19B ... Wiring wire 50 ... Bias power supply 51 ... Single lens type objective lens

Claims (8)

A hemispherical lens made of a material that transmits terahertz light, and provided with a flat surface perpendicular to the optical axis and a spherical surface centered on the optical axis;
A photoconductive antenna element that is flat and has an antenna pattern formed on a front main surface, and a point light source position of the antenna pattern is on the optical axis and abuts the flat surface of the hemispherical lens on the back main surface;
In a terahertz light receiving and emitting module comprising a module housing equipped with the photoconductive antenna element and the hemispherical lens,
An opening for exposing the antenna pattern;
For holding the element, wherein the opening is provided on the bottom surface of the recess, and the side surface of the recess is in contact with the side surface of the photoconductive antenna element to restrict the photoconductive antenna element from being displaced in a direction perpendicular to the optical axis. The concave portion and the concave portion for holding the element are provided on the bottom surface of the concave portion, and the side surface of the concave portion is brought into contact with the spherical surface of the hemispherical lens to restrict the hemispherical lens from being displaced in a direction perpendicular to the optical axis. A lens holding recess,
A mounting element provided along the optical axis;
A fixed cover that contacts the spherical surface of the hemispherical lens and holds the photoconductive antenna element and the hemispherical lens with the mount element;
A terahertz light receiving and emitting module.   2. The terahertz light receiving and emitting module according to claim 1, wherein the mount element has a recess depth of the element holding recess that is shallower than a thickness of the photoconductive antenna element.   The terahertz light receiving and emitting module according to claim 1, wherein the mount element has a thickness of 1 mm or less at the opening.   4. The terahertz light receiving and emitting module according to claim 2, wherein the terahertz light receiving and emitting module includes a buffer member in a gap surrounded by the mount element, the photoconductive antenna element, and the hemispherical lens.   The terahertz light receiving and emitting module according to claim 4, wherein the buffer member is an elastic member.   The terahertz light receiving and emitting module according to any one of claims 1 to 5, wherein the fixed cover has an opening having an opening diameter smaller than the diameter of the hemispherical lens.   The terahertz light receiving and emitting module according to claim 1, wherein the fixed cover is made of resin.   The module housing includes an attachment site for attaching the mount element, an opening for exposing the antenna pattern, and a connector for electrically connecting the antenna pattern to an external circuit, and the opening. The terahertz light receiving and emitting module according to claim 1, wherein the connector part and the antenna pattern are connected via a wiring wire passing through the part.

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