Method for rapid detection of terahertz wave linear polarization direction based on inner diameter gradually changing waveguide

Abstract

The application belongs to the technical field of terahertz wave linear polarization direction detection, and particularly discloses a terahertz wave linear polarization direction rapid detection method based on an inner diameter gradually changing waveguide. max continuously changes to a minimum value D min When the linear polarization terahertz wave is incident into the hollow waveguide, different linear polarization directions correspond to different hollow waveguide inner diameters D, and different hollow waveguide inner diameters D make the output spectrum of the terahertz wave have different resonance frequencies f; the terahertz single pulse signal output by the hollow waveguide is collected to obtain the resonance frequency f; and the linear polarization direction of the incident terahertz wave is deduced through the resonance frequency f. The application does not need the continuous rotation of a polarizer for measurement in the traditional method, and the linear polarization direction can be rapidly detected by a single terahertz pulse signal; only based on the inner diameter gradually changing waveguide, without special cladding design, the complexity and cost of the terahertz wave linear polarization direction detection device are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of terahertz wave linear polarization direction detection technology, and in particular to a rapid method for detecting the linear polarization direction of terahertz waves based on a waveguide with a gradually varying inner diameter. Background Technology

[0002] Terahertz waves typically refer to electromagnetic waves with frequencies in the range of 0.1 THz to 10 THz. Due to their advantages such as instantaneity, wide bandwidth, coherence, and penetrability to non-polar substances, terahertz technology is widely used in many fields such as medicine, biology, materials science, chemistry, military defense, and security inspection.

[0003] Especially in communications, the terahertz band is a core frequency band for future 6G communication technology. However, compared to other mature frequency bands, people are still exploring a series of issues related to the terahertz band, including the detection of linear polarization direction. Existing linear polarization detection methods require continuously rotating a terahertz polarizer to observe changes in the time-domain amplitude and finding the maximum signal amplitude to determine the linear polarization direction. Currently, there is no suitable method for detecting the linear polarization direction of a terahertz single pulse.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems existing in the background art. To this end, a method for rapid detection of the linear polarization direction of terahertz waves based on a waveguide with a gradually varying inner diameter is provided. This method utilizes the characteristic that linearly polarized light in different directions in a hollow waveguide will generate different resonant frequencies to achieve rapid detection of the linear polarization direction.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A fast method for detecting the linear polarization direction of terahertz waves based on a waveguide with a gradually varying inner diameter includes a hollow waveguide, wherein the inner diameter of the hollow waveguide varies from a maximum value D. max Continuous change to the minimum value D min When a linearly polarized terahertz wave is incident in a hollow waveguide, different linear polarization directions correspond one-to-one with different hollow waveguide inner diameters D. Different hollow waveguide inner diameters D result in different resonant frequencies f on the output spectrum of the terahertz wave. By acquiring the terahertz single-pulse signal output from the hollow waveguide, the resonant frequency f can be obtained. The linear polarization direction of the incident terahertz wave can be deduced from the resonant frequency f.

[0008] The following is a further defined technical solution of the present invention, wherein the maximum value D of the hollow waveguide inner diameter is... maxand minimum value D min The low-frequency cutoff frequency f of the detected linearly polarized signal low and high-frequency cutoff frequency f high It is determined by the following formula:

[0009]

[0010]

[0011] Where c is the speed of light in vacuum; θ is the angle between the linearly polarized light incident into the input port and the normal to the inner wall of the waveguide.

[0012] The following is a further defined technical solution of the present invention: the inner diameter D of the hollow waveguide is determined by the resonant frequency f of the detected linearly polarized signal using the following formula:

[0013]

[0014] Where c is the speed of light in vacuum; θ is the angle between the linearly polarized light incident into the input port and the normal to the inner wall of the waveguide.

[0015] Compared with the prior art, the present invention has the following technical effects:

[0016] This invention eliminates the need for continuous rotation of the polarizer in traditional methods, enabling rapid detection of linear polarization direction with a single terahertz pulse signal. Based solely on a waveguide with a gradually varying inner diameter, it eliminates the need for special cladding designs, significantly reducing the complexity and cost of terahertz wave linear polarization direction detection devices.

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 These are schematic diagrams illustrating two embodiments of the hollow waveguide in this invention; wherein, Figure 1 (a) is a hollow waveguide cross section consisting of two staggered semicircles; Figure 1 (b) is a hollow waveguide with a helical cross-section; D1, D2, and D3 are the waveguide inner diameters at different angles;

[0020] Figure 2 This is a schematic diagram of the detection system of the present invention; wherein, Figure 2(a) is the input linearly polarized time-domain signal. Figure 2 (b) is a hollow waveguide. Figure 2 (c) is a schematic diagram of the spectrum signal received by the receiver;

[0021] Figure 3 This is a diagram illustrating the linear polarization direction detection process of the present invention; wherein, Figure 3 (a) is the resonant frequency of the waveguide output. Figure 3 (b) is the inner diameter D calculated from the resonant frequency. Figure 3 (c) is a comparison between the linear polarization angle derived from the inner diameter D and the actual emitted linear polarization angle. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] like Figure 1-3 As shown, a fast method for detecting the linear polarization direction of terahertz waves based on waveguides with gradually varying inner diameters is provided, including hollow waveguides, such as... Figure 1 As shown, the hollow waveguide has two implementation methods: one where the hollow waveguide cross-section is composed of two staggered semicircles, and the other where the hollow waveguide cross-section has a helical structure. Both methods enable rapid detection of the linear polarization direction. In this embodiment, the hollow waveguide is selected... Figure 1 (a) is an example of a hollow waveguide structure.

[0024] The inner diameter of the hollow waveguide starts from the maximum value D. max Continuous change to the minimum value D min When a linearly polarized terahertz wave is incident in a hollow waveguide, different linear polarization directions correspond one-to-one with different hollow waveguide inner diameters D. Different hollow waveguide inner diameters D result in different resonant frequencies f on the output spectrum of the terahertz wave. By acquiring the terahertz single-pulse signal output from the hollow waveguide, the resonant frequency f can be obtained. The linear polarization direction of the incident terahertz wave can be deduced from the resonant frequency f.

[0025] Maximum value D of hollow waveguide inner diameter max and minimum value D min The low-frequency cutoff frequency f of the detected linearly polarized signal low and high-frequency cutoff frequency f high It is determined by the following formula:

[0026]

[0027]

[0028] Among them, f low It is the low-frequency cutoff frequency of the input terahertz wave, 0.20 THz; f high It is a high-frequency cutoff frequency of 0.25THz; D max The maximum waveguide inner diameter is 12mm; D min The minimum inner diameter is 10 mm; c is the speed of light in a vacuum, which is 3 × 10⁻⁶. 8 m / s; θ is the angle between the linearly polarized light incident inside the input port and the normal to the inner wall of the waveguide, which is 86.5°.

[0029] Figure 2 (a) Terahertz waves with different linear polarization directions, grazing ingress Figure 2 (b) represents a resonant device with a hollow waveguide that generates resonances at different frequencies, and then outputs... Figure 2 (c); Figure 2 As can be seen in (c), different linear polarization directions correspond to different resonant frequencies, namely 0.24THz, 0.23THz and 0.21THz.

[0030] Will Figure 2 The resonant frequencies of the three outputs in (c) are represented by a histogram, yielding the following results. Figure 3 (a) Substituting the resonant frequency into the formula:

[0031]

[0032] The inner diameter D of the hollow waveguide can be obtained as 10.1mm, 10.9mm, and 11.9mm, such as... Figure 3 As shown in (b). Based on the obtained inner diameter, the inverse linear polarization angles are 4°, 87°, and 139°, as follows: Figure 3 The cylinders in (c) have actual polarization angles of 0°, 90°, and 135°, such as Figure 3 The triangular markers in (c) should be placed in... Figure 3 (c) By comparison, it can be seen that the linear polarization angle derived from our inner diameter is close to the actual polarization angle.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present invention, or modify it into equivalent embodiments, without departing from the scope of the present invention's technical solution. Therefore, all equivalent changes made based on the shape, structure, and principle of the present invention without departing from the scope of the present invention's technical solution should be covered within the protection scope of the present invention.

Claims

1. A method for rapid detection of the linear polarization direction of terahertz waves based on a waveguide with a gradually varying inner diameter, characterized in that, Includes a hollow waveguide, the inner diameter of which ranges from a maximum value D. max Continuous change to the minimum value D min When a linearly polarized terahertz wave is incident in a hollow waveguide, different linear polarization directions correspond one-to-one with different hollow waveguide inner diameters D. Different hollow waveguide inner diameters D result in different resonant frequencies f on the output spectrum of the terahertz wave. By acquiring the terahertz single-pulse signal output from the hollow waveguide, the resonant frequency f can be obtained. The linear polarization direction of the incident terahertz wave can be deduced from the resonant frequency f.

2. The method for rapid detection of terahertz wave linear polarization direction based on a waveguide with gradually varying inner diameter according to claim 1, characterized in that, The maximum value D of the hollow waveguide inner diameter max and minimum value D min The low-frequency cutoff frequency f of the detected linearly polarized signal low and high-frequency cutoff frequency f high It is determined by the following formula: Where c is the speed of light in vacuum; θ is the angle between the linearly polarized light incident into the input port and the normal to the inner wall of the waveguide.

3. The method for rapid detection of terahertz wave linear polarization direction based on a waveguide with a gradually varying inner diameter according to claim 1, characterized in that, The inner diameter D of the hollow waveguide is determined by the resonant frequency f of the detected linearly polarized signal using the following formula: Where c is the speed of light in vacuum; θ is the angle between the linearly polarized light incident into the input port and the normal to the inner wall of the waveguide.

Images