Transmitting and receiving integrated terahertz focusing lens based on THz-TDS

Abstract

The invention discloses a transmitting and receiving integrated terahertz focusing lens based on THz-TDS, and the transmitting and receiving integrated terahertz focusing lens is of an integrated structure, and comprises a light beam parallel part and a light beam focusing part which are coaxially arranged. The light beam parallel part is composed of an upper half lens and a lower half lens which are of the same structure, and the upper half lens and the lower half lens are symmetrically arranged at the front end of the light beam focusing part up and down with the optical axis of the light beam focusing part as the symmetry axis. An incident light beam enters a lower half lens of the light beam parallel part, so that the light beam is continuously propagated to the light beam focusing part as a parallel light beam, is refracted at the light beam focusing part and is transmitted to a to-be-detected target, and the light beam is reflected by the to-be-detected target, penetrates through the transmitting-receiving integrated terahertz focusing lens and reaches the photoconductive detector. According to the invention, the terahertz wave beam can be focused again, the radiation energy loss is greatly reduced, the installation and adjustment difficulty of the terahertz time-domain spectroscopy system is effectively reduced, and the system stability is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz reflective optical systems, and particularly relates to a transceiver integrated terahertz focusing lens based on THz-TDS. Background Art

[0002] At present, most terahertz time-domain spectroscopy systems use off-axis parabolic mirrors or beam splitters to propagate terahertz pulses in space. If an off-axis parabolic mirror is used, the structure is complex, the geometric size is large, and at the same time, its cost is high, and it is difficult to replace different focal lengths, lacking flexibility.

[0003] If a beam splitter is used, the terahertz beam passes through the beam splitter and is focused on the sample to be measured. It is reflected by the metal plate at the bottom of the sample to be measured and then reflected by the beam splitter again to reach the terahertz detector. Passing through the beam splitter twice will also cause a large amount of terahertz pulse loss. Summary of the Invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a transceiver integrated terahertz focusing lens based on THz-TDS. It is an integrated structure, composed of a beam parallel part and a beam focusing part. After the terahertz beam is preliminarily focused by a hemispherical silicon lens, it is focused on the sample to be measured by the transceiver integrated terahertz lens of the present invention. After the beam is reflected by the metal plate at the bottom of the sample to be measured, it passes through the transceiver integrated terahertz lens of the present invention again and is received by a photoconductive detector. And common lens materials in the terahertz band such as HPX, HDPE, cross-linked polystyrene, etc. can all be applicable in the design. The present invention can refocus the terahertz beam. The transceiver integrated structure can greatly reduce the radiation energy loss, effectively reduce the alignment difficulty of the terahertz time-domain spectroscopy system, improve the system stability, and the lens structure is simple and the components are easy to process.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] Provide a transceiver integrated terahertz focusing lens based on THz-TDS. The transceiver integrated terahertz focusing lens is an integrated structure, including a beam parallel part and a beam focusing part arranged coaxially; the beam parallel part is composed of an upper half lens and a lower half lens with the same structure. The upper half lens and the lower half lens are symmetrically arranged above and below the front end of the beam focusing part with the optical axis of the beam focusing part as the symmetry axis. When in use, the incident beam is incident on the lower half lens of the beam parallel part, so that the beam continues to propagate as a parallel beam to the beam focusing part. The beam is refracted in the beam focusing part and transmitted to the target to be measured. After the beam is reflected by the target to be measured, it is incident on the beam focusing part and refracted to the upper half lens of the beam parallel part, and finally reaches the photoconductive detector through the upper half lens.

[0007] Further, a transceiver integrated terahertz focusing lens based on THz-TDS as described in claim 1, characterized in that the transceiver integrated terahertz focusing lens further comprises a lens mounting limiting plate, and the lens mounting limiting plate is arranged on the outer periphery of the junction of the beam parallel part and the beam focusing part, and is an integrally formed structure with the transceiver integrated terahertz focusing lens.

[0008] Further, for the terahertz beam incident in parallel, the focal length of the beam focusing part conforms to the focal length formula of a plano-convex lens:

[0009]

[0010] In the formula, f is the focal length of the beam focusing part, n is the refractive index, and R is the radius of curvature.

[0011] Further, both the beam parallel part and the beam focusing part are made of TPX material, and the refractive index is 1.462.

[0012] The working principle of the present invention is as follows:

[0013] The terahertz beam is initially focused by a hyperhemispherical silicon lens and then enters the lower half lens of the beam parallel part of the transceiver integrated terahertz focusing lens of the present invention. The divergence angle of the beam is further reduced by the lower half lens, so that the beam can be converged on the sample to be measured as an approximate parallel beam. After passing through the beam parallel part, the beam continues to propagate, is refracted in the beam focusing part and transmitted to the target to be measured. The beam is reflected by the target to be measured to the beam focusing part of the transceiver integrated terahertz focusing lens of the present invention, and is refracted to the upper half lens of the beam parallel part, and finally reaches the photoconductive detector through the lens.

[0014] The divergence angle of the incident terahertz beam can be reduced by adjusting the radius of curvature and refractive index of the beam parallel part, so that the beam can be converged on the sample to be measured as an approximate parallel beam. Different working distances of the lens can be obtained by adjusting the radius of curvature and refractive index of the beam focusing part, so that the lens can meet the measurement focal lengths in different scenarios.

[0015] The present invention has the following beneficial effects:

[0016] The present invention adopts an integrated structure, and a lens with a transceiver integrated structure is formed by combining the beam parallel part and the beam focusing part, reducing the optical path of the spatial propagation of the terahertz pulse, thereby greatly reducing the radiation energy loss.

[0017] The present invention adopts a lens with a transceiver integrated structure, avoiding the use of multiple expensive off-axis parabolic mirrors, effectively reducing the alignment difficulty of the terahertz time-domain spectroscopy system, and improving the system stability and miniaturization.

[0018] The present invention can obtain different working distances of the lens by adjusting the curvature radius and refractive index of the beam focusing part, so that the lens can meet the measurement focal lengths in different scenarios. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings to be used in the description of the embodiments of the present invention. Obviously, the following-described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings.

[0020] Figure 1 Structural schematic diagram of the transceiver integrated terahertz focusing lens based on THz-TDS according to the present invention;

[0021] Figure 2 Structural diagram of the transceiver integrated terahertz focusing lens of THz-TDS according to the embodiment of the present invention;

[0022] Figure 3 Schematic diagram of the working principle of the transceiver integrated terahertz focusing lens based on THz-TDS according to the present invention;

[0023] Figure 4 Irradiance diagram of the photoconductive detector when using a beam splitter;

[0024] Figure 5 Irradiance diagram of the photoconductive detector when using the transceiver integrated terahertz focusing lens of THz-TDS according to the embodiment of the present invention;

[0025] In the figure:

[0026] 1 - Beam parallel part; 2 - Beam focusing part; 11 - Upper half lens; 12 - Lower half lens; 21 - Solid lens mounting limit plate. Detailed Embodiments

[0027] The following will further illustrate the solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the present invention are shown in the drawings rather than all the structures.

[0028] In the description of this embodiment, the orientation or positional relationship terms such as "upper" and "lower" are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description and simplifying the operation, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0029] Embodiment

[0030] As Figure 1 、 Figure 2 shown, this embodiment is a transceiver integrated terahertz focusing lens based on THz - TDS, which is an integrated structure, including a beam parallel part 1 and a beam focusing part 2 arranged coaxially; the beam parallel part 1 is composed of an upper half lens 11 and a lower half lens 12 with the same structure. The upper half lens 11 and the lower half lens 12 are symmetrically arranged above and below with the optical axis of the beam focusing part 2 as the symmetry axis at the front end of the beam focusing part 2. When in use, the incident beam is incident on the lower half lens of the beam parallel part, so that the beam can continue to propagate as an approximate parallel beam to the beam focusing part. The beam refracts in the beam focusing part and is transmitted to the target to be measured. After the beam is reflected by the target to be measured, it is incident on the beam focusing part and refracts to the upper half lens of the beam parallel part, and finally reaches the photoconductive detector after passing through the upper half lens, as Figure 3 shown.

[0031] Furthermore, in order to improve the efficiency of replacing the terahertz focusing lens, the transceiver integrated terahertz focusing lens further includes a lens mounting limit plate 21. The lens mounting limit plate 21 is arranged on the outer periphery of the junction of the beam parallel part 1 and the beam focusing part 2, and is an integrally formed structure with the transceiver integrated terahertz focusing lens, as Figure 2 shown.

[0032] Furthermore, by adjusting the curvature radius and refractive index of the beam parallel part 1, the divergence angle of the incident terahertz beam can be reduced, so that the beam can be converged on the sample to be measured as an approximate parallel beam.

[0033] Furthermore, by adjusting the curvature radius and refractive index of the beam focusing part 2, different working distances of the lens can be obtained, so that the lens can meet the measurement focal lengths in different scenarios.

[0034] Furthermore, for the approximately parallel incident terahertz beam, the focal length of the beam focusing part conforms to the focal length formula of a plano - convex lens:

[0035]

[0036] In the formula, f is the focal length of the beam focusing part, n is the refractive index, and R is the curvature radius.

[0037] Furthermore, in this embodiment, both the beam parallel part and the beam focusing part 2 are made of TPX material, with a refractive index of 1.462. The distance from the photoconductive emitter to the terahertz lens is z = 45 mm, the working distance of the lens is f = 90 mm, and the distance between the photoconductive emitter and the photoconductive detector is a = 22 mm.

[0038] In the comparative experiment, the total luminous flux of the light source is set to 1 W. Through simulation calculation, the irradiance diagrams of the photoconductive detector using a beam splitter and the photoconductive detector using the transceiver integrated terahertz focusing lens described in this embodiment are respectively as Figure 4 and Figure 5 shown. It can be seen that the power of the central spot of the photoconductive detector is higher when using the transceiver integrated terahertz focusing lens.

[0039] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A terahertz focusing lens with integrated transceiver based on THz-TDS, characterized in that: The transceiver-integrated terahertz focusing lens is an integrated structure, comprising a coaxially arranged beam paralleling portion (1) and a beam focusing portion (2); the beam paralleling portion (1) is composed of an upper half lens (11) and a lower half lens (12) of identical structure, the upper half lens (11) and the lower half lens (12) being symmetrically arranged at the front end of the beam focusing portion (2) with the optical axis of the beam focusing portion (2) as the symmetry axis; when in use, an incident light beam is incident on the lower half lens of the beam paralleling portion, so that the light beam continues to propagate to the beam focusing portion as a parallel light beam, the light beam is refracted in the beam focusing portion and transmitted to a target to be measured, the light beam is reflected by the target to be measured, is incident on the beam focusing portion, and is refracted to the upper half lens of the beam paralleling portion, passes through the upper half lens and finally reaches a photoconductive detector.

2. The THz-TDS-based terahertz focusing lens for transmitting and receiving as claimed in claim 1, characterized in that: The transceiver-integrated terahertz focusing lens further comprises a lens installation limit plate (21), which is arranged at the periphery of the junction of the light beam parallel portion (1) and the light beam focusing portion (2), and forms an integrally formed structure with the transceiver-integrated terahertz focusing lens.

3. The THz-TDS-based terahertz focusing lens for transmitting and receiving as claimed in claim 1, characterized in that: For a parallel incident terahertz beam, the focal length of the focused portion of the beam conforms to the focal length formula of a plano-convex lens: Where f is the focal length of the focused portion of the beam, n is the refractive index, and R is the radius of curvature.

4. The THz-TDS-based terahertz focusing lens with integrated transceiver as claimed in claim 1, characterized in that: The light beam parallel part (1) and the light beam focusing part (2) are both made of TPX material with a refractive index of 1.462.

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