A miniaturized integrated terahertz transmitting and receiving probe structure

Abstract

The present invention belongs to the field of terahertz technology, and specifically relates to a miniaturized integrated terahertz transmitting and receiving probe structure. The probe structure includes a front panel, a rear panel, a photoconductive antenna, a fixed bracket, an off-axis parabolic metal reflector group, a fixed plate, a bottom plate, and a protective shell. The fixed bracket adjusts and fixes the angle of the photoconductive antenna, and the fixed plate adjusts and fixes the angle of the off-axis parabolic metal reflector. By adjusting the photoconductive antenna and the off-axis parabolic metal reflector group, the emission, collimation, convergence and reception of terahertz radiation are realized. The probe "folds" the previous planar optical path structure, reduces the volume of the terahertz transmitting and receiving module, has a compact structure, and is easy to carry, fix and use.

Description

Technical Field

[0001] The present invention belongs to the field of terahertz technology, and in particular relates to a miniaturized integrated terahertz transmitting and receiving probe structure. Background Art

[0002] Terahertz radiation (THz) usually refers to electromagnetic waves with a frequency range of 0.1-10THz, which is between millimeter waves and infrared waves, and is in the far-infrared band. Terahertz radiation occupies a very special position in the electromagnetic spectrum. It is not only the transition zone from macroscopic classical theory to microscopic quantum theory, but also the transition zone from electronics to photonics. Compared with electromagnetic waves in other bands, terahertz waves have good penetration ability for most dielectrics and non-polar substances, and can perform non-destructive testing on such substances; terahertz has good coherence, and the use of coherent measurement technology can directly measure the electric field information of an object, and its optical parameters can be obtained through simple data processing; in addition, terahertz waves also have excellent characteristics such as low energy, good transient properties, and large bandwidth.

[0003] The terahertz time-domain spectroscopy system is currently the main instrument for the application of terahertz waves in the field of non-destructive testing. It consists of a femtosecond laser, a delay line, a data acquisition system, and a terahertz transmitting and receiving module. Due to the limited space in the actual use scenario, the volume of the terahertz transmitting and receiving module determines the actual use effect of the terahertz time-domain spectroscopy system, which means that the volume of the terahertz transmitting and receiving module must be as small as possible. In the past, most terahertz transmitting and receiving modules used a planar optical path structure, which was large in size and not conducive to practical application. Summary of the invention

[0004] Purpose of the invention: To provide a miniaturized integrated terahertz transmitting and receiving probe structure to reduce the volume of the terahertz transmitting and receiving module while maintaining the function unchanged, so as to solve the problem that the existing terahertz transmitting and receiving module is not conducive to practical application due to its large volume.

[0005] Technical solution:

[0006] In the first aspect, a miniaturized integrated terahertz transmitting and receiving probe structure is provided, comprising: a front panel 1, a rear panel 2, a fixing bracket 3, a transmitting photoconductive antenna 4, a receiving photoconductive antenna 5, an upper fixing plate 6, a lower fixing plate 7, an off-axis parabolic metal reflector group 8, a bottom plate 9, and a protective shell 10, wherein the front panel 1, the rear panel 2, the bottom plate 9, and the protective shell 10 constitute an external frame of the probe structure, the front panel 1 is processed with a square opening for allowing terahertz radiation to pass through, the off-axis parabolic metal reflector group 8 is fixed to the bottom plate 9 and the protective shell 10 through the upper fixing plate 6 and the lower fixing plate 7, the fixing bracket 3 is arranged on the bottom plate 9 and is located behind the off-axis parabolic metal reflector group 8, and the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 are fixed on the fixing bracket 3, so as to realize the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5. In order to adjust and fix the angles in the horizontal and vertical directions and adjust the distance to the off-axis parabolic metal reflector group 8, the rear panel 2 is processed with circular openings for fixing optical fibers, power lines and signal lines.

[0007] Furthermore, the fixing bracket 3 includes two L-shaped plates and two C-shaped clamps, the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 are respectively arranged in the two C-shaped clamps, and a plurality of threaded holes are arranged above the C-shaped clamps. A plurality of adjusting screws pass through the plurality of threaded holes to adjust and fix the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 in the front-to-back direction. A waist-shaped hole is arranged on the side of the L-shaped plate, and the height and rotation angle of the C-shaped clamp in the vertical direction are adjusted and fixed by screws passing through the waist-shaped holes and screw holes.

[0008] Furthermore, the bottom plate 9 and the L-shaped plate of the fixing bracket 3 are connected by screws to adjust and fix the horizontal rotation angle of the fixing bracket 3 .

[0009] Furthermore, the polarization directions of the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 are consistent.

[0010] Furthermore, the lower fixing plate 7 is fixed to the base plate 9 by screws, and the upper fixing plate 6 is fixed to the protective shell 10 by screws. Each fixing plate includes a plurality of hollow structures corresponding to the screw holes on the back of the two off-axis parabolic metal reflectors. The rotation angle of the off-axis parabolic metal reflector can be adjusted and fixed by adjusting the position of the screws in the hollow structure.

[0011] Furthermore, the off-axis parabolic metal reflector group 8 includes a first off-axis parabolic metal reflector 11 and a second off-axis parabolic metal reflector 12 corresponding to the transmitting photoconductive antenna 4, and a third off-axis parabolic metal reflector 13 and a fourth off-axis parabolic metal reflector 14 corresponding to the receiving photoconductive antenna 5. The first off-axis parabolic metal reflector 11 parallelizes and collimates the terahertz radiation emitted by the transmitting photoconductive antenna 4; the collimated terahertz radiation reaches the second off-axis parabolic metal reflector 12 for convergence, the converged terahertz radiation is reflected by the object and reaches the third off-axis parabolic metal reflector 13, is collimated by the third off-axis parabolic metal reflector 13 and reaches the fourth off-axis parabolic metal reflector 14, and is finally converged by the fourth off-axis parabolic metal reflector 14 to reach the receiving photoconductive antenna 5.

[0012] Furthermore, the emission angle of the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 is 12.5°.

[0013] Further, the distance from the center of the first off-axis parabolic metal reflector 11 to the center of the transmitting photoconductive antenna 4 is its focal length, and the distance from the center of the fourth off-axis parabolic metal reflector 14 to the center of the receiving photoconductive antenna 5 is its focal length.

[0014] Beneficial effects:

[0015] By designing a mechanical structure to "fold" the planar optical path, the volume of the terahertz transmitting and receiving module is reduced while maintaining its function, solving the problem that the existing terahertz transmitting and receiving modules are large and not conducive to practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a general diagram of a probe according to an embodiment of the present invention;

[0017] Figure 2 It is a schematic diagram of the plane optical path of the off-axis parabolic metal reflector group;

[0018] Figure 3 is a front view of a probe according to an embodiment of the present invention;

[0019] Among them, 1 is a front panel, 2 is a rear panel, 3 is a fixing bracket, 4 is a transmitting photoconductive antenna, 5 is a receiving photoconductive antenna, 6 is an upper fixing plate, 7 is a lower fixing plate, 8 is an off-axis parabolic metal reflector group, 9 is a bottom plate, 10 is a protective shell, a first off-axis parabolic metal reflector 11, a second off-axis parabolic metal reflector 12, a third off-axis parabolic metal reflector 13, and a fourth off-axis parabolic metal reflector 14. DETAILED DESCRIPTION

[0020] The invention discloses a miniaturized integrated terahertz transmitting and receiving probe structure, which is a probe device suitable for a fiber-coupled terahertz time-domain spectroscopy system (THz-TDS). The probe structure consists of a front panel, a rear panel, a photoconductive antenna, a fixed bracket, an off-axis parabolic metal reflector group, a fixed plate, a bottom plate, a protective shell, etc. The fixed bracket has the function of adjusting and fixing the angle of the photoconductive antenna, and the fixed plate has the function of adjusting and fixing the angle of the off-axis parabolic metal reflector. By adjusting the photoconductive antenna and the off-axis parabolic metal reflector group, the emission, collimation, convergence and reception of terahertz radiation are realized. The probe "folds" the previous planar optical path structure, reduces the volume of the terahertz transmitting and receiving module, has a compact structure, is easy to carry, fix and use, is an important component of the fiber-coupled terahertz time-domain spectroscopy system, and is a key development direction for the terahertz time-domain spectroscopy technology to move towards practical application.

[0021] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0022] A miniaturized integrated terahertz transmitting and receiving probe structure is used to realize the emission, collimation, convergence and reception of terahertz radiation. Figures 1 to 3 The probe comprises: a front panel 1, wherein the front panel 1 is processed with a square opening for protecting an off-axis parabolic metal reflector group 8 without blocking terahertz radiation; a rear panel 2, wherein the rear panel 2 is processed with a circular opening for fixing optical fibers, power lines and signal lines; a fixing bracket 3, wherein the fixing bracket 3 is used to adjust and fix the angles of a transmitting photoconductive antenna 4 and a receiving photoconductive antenna 5 in the horizontal and vertical directions, and can also adjust the distance from the antenna to the off-axis parabolic metal reflector group 8 to adapt to different types of antennas; and the transmitting photoconductive antenna 4 is included. The photoconductive antenna 5 is used for transmitting and receiving terahertz radiation; each of the upper fixing plate 6 and the lower fixing plate 7 includes 6 hollow structures corresponding to the screw holes on the back of the two off-axis parabolic metal reflectors, and the rotation angle of the off-axis parabolic metal reflector group can be adjusted and fixed by adjusting the position of the screws in the hollow structure; the off-axis parabolic metal reflector group 8, the off-axis parabolic metal reflector 8 is used to realize the collimation and convergence of terahertz radiation, and the off-axis parabolic metal reflector group 8 includes 4 off-axis Parabolic metal reflector, the first off-axis parabolic metal reflector 11 parallelizes and collimates the terahertz radiation emitted by the transmitting photoconductive antenna 4; the collimated terahertz radiation reaches the second off-axis parabolic metal reflector 12 for convergence, and the converged terahertz radiation is reflected by the object and reaches the third off-axis parabolic metal reflector 13, and then reaches the fourth off-axis parabolic metal reflector 14 after being collimated by the third off-axis parabolic metal reflector 13, and finally is converged by the fourth off-axis parabolic metal reflector 14 to reach the receiving photoconductive antenna 5.

[0023] The sizes and focal lengths of the first off-axis parabolic metal reflector 11, the second off-axis parabolic metal reflector 12, the third off-axis parabolic metal reflector 13, and the fourth off-axis parabolic metal reflector 14 can be selected according to actual system requirements, wherein the focal lengths of the first off-axis parabolic metal reflector 11 and the fourth off-axis parabolic metal reflector 14 must be equal, the focal lengths of the second off-axis parabolic metal reflector 12 and the third off-axis parabolic metal reflector 13 must be equal, and the off-axis parabolic metal reflectors 12 and 13 are symmetrically distributed relative to the central axis of the upper fixed plate 6. The distances from the centers of the first off-axis parabolic metal reflector 11 and the fourth off-axis parabolic metal reflector 14 to the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 are respectively about their focal lengths; the distance from the center of the off-axis parabolic metal reflector 11 to the center of the off-axis parabolic metal reflector 12 = (the optical path of the femtosecond laser detected by the terahertz time-domain spectrometer - the optical path of the femtosecond laser pumped by the time-domain spectrometer - the sum of the focal lengths of all off-axis parabolic metal reflectors) / 2; a bottom plate 9, the bottom plate 9 is used to fix the entire probe structure; a protective shell 10, the protective shell 10 is used to protect the entire probe structure.

[0024] The fixed bracket 3 includes an L-shaped plate and a C-shaped clamp. The C-shaped clamp adjusts and fixes the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 in the front and rear directions by adjusting three screws. The L-shaped plate adjusts and fixes the height and rotation angle of the C-shaped clamp (including the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5) in the vertical direction through a long screw hole and a screw. The bottom plate adjusts and fixes the horizontal rotation angle of the fixed bracket 3 (including the L-shaped plate, the C-shaped clamp, the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5) through a screw.

[0025] The polarization directions of the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 must be consistent.

[0026] The lower fixing plate 7 is fixed to the bottom plate 9 by screws, and the upper fixing plate 6 is fixed to the protective shell 10 by screws. Each fixing plate includes 6 hollow structures corresponding to the screw holes on the back of the two off-axis parabolic metal reflectors, and the rotation angle of the off-axis parabolic metal reflector can be adjusted and fixed by adjusting the position of the screws in the hollow structure.

[0027] The sizes and focal lengths of the first off-axis parabolic metal reflector 11 , the second off-axis parabolic metal reflector 12 , the third off-axis parabolic metal reflector 13 , and the fourth off-axis parabolic metal reflector 14 can be selected according to actual system requirements. Specific idea: the emission angle of the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 is 12.5°. When the distance from the center is s, the spot diameter of the terahertz radiation is tan(12.5°) ×s×2. By analyzing the spot size and the probe size requirements, the first off-axis parabolic metal reflector 11 and the fourth off-axis parabolic metal reflector 14 are selected to have a size of 1 inch and a focal length of 50.4 mm; according to the actual distance requirement between the object to be measured and the probe, the second off-axis parabolic metal reflector 12 and the third off-axis parabolic metal reflector 13 are selected to have a size of 1 inch and a focal length of 100.8 mm, and the off-axis parabolic metal reflectors 12 and 13 are symmetrically distributed relative to the central axis of the upper fixed plate 6. At the same time, in order to reduce the loss of the mirror to terahertz radiation, gold film is selected on the surface of all axis parabolic metal reflectors.

[0028] The distance from the center of the off-axis parabolic metal reflector 11 to the center of the transmitting photoconductive antenna 4 is about its focal length, and the distance from the center of the off-axis parabolic metal reflector 14 to the center of the receiving photoconductive antenna 5 is also about its focal length.

[0029] The distance from the center of the off-axis parabolic metal reflector 11 to the center of the off-axis parabolic metal reflector 12 = (the optical path of the femtosecond laser detected by the terahertz time-domain spectrometer - the optical path of the femtosecond laser pumped by the time-domain spectrometer - the sum of the focal lengths of all off-axis parabolic metal reflectors) / 2, and the distance from the center of the off-axis parabolic metal reflector 13 to the center of the off-axis parabolic metal reflector 14 is the same as described above.

[0030] By designing the mechanical structure, the previous planar optical path is "folded", which reduces the volume of the optical path structure while ensuring the function remains unchanged, making it more conducive to practical applications.

[0031] First, fix the fixing bracket 3 on the bottom plate 9 by screws, then fix the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 on the two fixing brackets 3 by screws, and adjust the screws on the fixing bracket 3 to keep the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 aligned in the horizontal and vertical directions. Determine the positions of the upper fixing plate 6 and the lower fixing plate 7 according to the height of the transmitting photoconductive antenna 4 and the receiving photoconductive antenna 5 and the calculated spacing between the off-axis parabolic metal reflectors 11 and 12, and fix them, and adjust the rotation angle of the off-axis parabolic metal reflector group 8 by screws of the upper fixing plate 6 and the lower fixing plate 7, wherein the distance from the first off-axis parabolic metal reflector 11 and the fourth off-axis parabolic metal reflector 14 to the transmitting photoconductive antenna 4 or the receiving photoconductive antenna 5 is about the focal length value thereof, and fix the off-axis parabolic metal reflector group 8 after the adjustment is completed; finally, assemble the front panel 1, the rear panel 2, the bottom plate 9 and the protective shell 10, etc., to complete the probe construction.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. Compared with the terahertz transmitting and receiving modules composed of the previous planar optical path structure, the probe proposed in the present invention has a compact structure, a small size, and is easy to carry, fix and use.

[0034] 2. An engineering method is proposed in which a mechanical structure can be used to "fold" a planar symmetrical optical path structure to reduce the volume of the optical path.

Claims

1. A miniaturized integrated terahertz transmitting and receiving probe structure, characterized in that: include: A front panel (1), a rear panel (2), a fixing bracket (3), a transmitting photoconductive antenna (4), a receiving photoconductive antenna (5), an upper fixing plate (6), a lower fixing plate (7), an off-axis parabolic metal reflector group (8), a bottom plate (9), and a protective shell (10), wherein the front panel (1), the rear panel (2), the bottom plate (9), and the protective shell (10) constitute an external frame of a probe structure, the front panel (1) is processed with a square opening for allowing terahertz radiation to pass through, the off-axis parabolic metal reflector group (8) is fixed to the bottom plate (9) and the protective shell (10) through the upper fixing plate (6) and the lower fixing plate (7), and the fixing bracket (3) is arranged on the bottom plate (9) and is located behind the off-axis parabolic metal reflector group (8); a transmitting photoconductive antenna (4) and a receiving photoconductive antenna (5) are fixed on the fixing bracket (3) for adjusting and fixing the transmitting photoconductive antenna (4) and the receiving photoconductive antenna (5) in the horizontal and vertical directions and adjusting the distance to the off-axis parabolic metal reflector group (8); the rear panel (2) is processed with a circular opening for fixing the optical fiber, the power line and the signal line; the off-axis parabolic metal reflector group (8) includes a first off-axis parabolic metal reflector (11) corresponding to the transmitting photoconductive antenna (4) and A second off-axis parabolic metal reflector (12), and a third off-axis parabolic metal reflector (13) and a fourth off-axis parabolic metal reflector (14) corresponding to the receiving photoconductive antenna (5); the first off-axis parabolic metal reflector (11) parallelizes and collimates the terahertz radiation emitted by the transmitting photoconductive antenna (4); the collimated terahertz radiation reaches the second off-axis parabolic metal reflector (12) for convergence; the converged terahertz radiation is reflected by an object and reaches the third off-axis parabolic metal reflector (13); after being collimated by the third off-axis parabolic metal reflector (13), it reaches the fourth off-axis parabolic metal reflector (14), and finally converged by the fourth off-axis parabolic metal reflector (14) to reach the receiving photoconductive antenna (5), the fixing bracket (3) comprises two L-shaped plates and two C-shaped clamps, the transmitting photoconductive antenna (4) and the receiving photoconductive antenna (5) are respectively arranged in the two C-shaped clamps, a plurality of threaded holes are arranged above the C-shaped clamps, a plurality of adjusting screws pass through the plurality of threaded holes to adjust and fix the transmitting photoconductive antenna (4) and the receiving photoconductive antenna (5) in the front and rear directions, a waist-shaped hole is arranged on the side of the L-shaped plate, and screws pass through the waist-shaped hole and the screw hole to adjust and fix the height and rotation angle of the C-shaped clamp in the vertical direction.

2. The probe structure according to claim 1, characterized in that: The bottom plate (9) and the L-shaped plate of the fixed bracket (3) are connected by screws to achieve adjustment and fixation of the horizontal rotation angle of the fixed bracket (3).

3. The probe structure according to claim 1, characterized in that: The polarization directions of the transmitting photoconductive antenna (4) and the receiving photoconductive antenna (5) are consistent.

4. The probe structure according to claim 1, characterized in that: The lower fixing plate (7) is fixed to the bottom plate (9) by screws, and the upper fixing plate (6) is fixed to the protective shell (10) by screws. Each fixing plate includes a plurality of hollow structures corresponding to the screw holes on the backs of the two off-axis parabolic metal reflectors. The rotation angle of the off-axis parabolic metal reflector can be adjusted and fixed by adjusting the position of the screws in the hollow structure.

5. The probe structure according to claim 1, characterized in that: The emission angle of the transmitting photoconductive antenna (4) and the receiving photoconductive antenna (5) is 12.5°.

6. The probe structure according to claim 4, characterized in that: The distance from the center of the first off-axis parabolic metal reflector (11) to the center of the transmitting photoconductive antenna (4) is its focal length value, and the distance from the center of the fourth off-axis parabolic metal reflector (14) to the center of the receiving photoconductive antenna (5) is its focal length value.

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