Rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling

Abstract

The invention relates to the technical field of terahertz wave generation and transmission, in particular to a rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling. The photoconductive mixer comprises a photoconductive substrate used for exciting carriers through a photoconductive effect; the metal planar antenna is arranged on the first surface of the photoconductive substrate and is used for converting carrier current into a terahertz radiation signal; the effective medium silicon waveguides are arranged on the second surface and the two side faces of the photoconductive substrate in a coupling mode, and the second surface is opposite to the first surface; the rectangular waveguide is used for receiving and outputting a terahertz signal; the effective medium silicon waveguide comprises a waveguide core and air hole arrays distributed on the two sides of the waveguide core, and the air hole arrays are configured to enable the effective medium silicon waveguide to form a refractive index gradient so as to constrain transmission of signals in the waveguide core. By adopting the method, rectangular waveguide output can be efficiently realized, and the method has the characteristic of high structural integration degree.

Description

Technical Field

[0001] This application relates to the field of terahertz wave generation and transmission technology, and in particular to a rectangular waveguide output type optoconductive mixer based on effective dielectric silicon waveguide coupling. Background Technology

[0002] In recent years, due to the increasing demand for terahertz wave technology in modern electronic systems such as communication, remote sensing, and radar, the operating frequency bands of many electronic devices have expanded to terahertz waves (100 ~ 10000 GHz). Terahertz noise sources can be used as calibration sources or signal sources, and have a wide range of applications in terahertz radiometer calibration and electronic device noise figure testing.

[0003] Traditional noise sources mainly include hot and cold noise sources and electronics-based solid-state noise sources. Hot and cold noise sources have a low noise-to-noise ratio and are only used for microwave radiometer calibration and noise figure testing of low-noise devices. Solid-state noise sources mainly utilize reverse-biased avalanche diodes to generate and output noise. The output noise spectrum is not adjustable and decreases sharply with increasing frequency. Therefore, solid-state noise sources with broadband noise output often have extremely poor noise flatness.

[0004] The application of photonic noise source technology can effectively solve the above problems. Compared with existing traditional noise sources, photonic noise sources consist of spectrally controllable incoherent light sources and photodetectors that achieve photoelectric conversion, offering advantages such as controllable noise power spectrum, a wide operating frequency range, and high power. Therefore, photonic noise sources, which combine high noise-to-noise ratio and good flatness, are the preferred solution for realizing terahertz noise sources. However, the 325-500 GHz band, as the mid-to-high frequency band of terahertz (THz) waves, possesses characteristics such as ultra-high bandwidth (175 GHz), high spatial resolution, and strong penetration, but the efficient generation and transmission of its electromagnetic waves has always been a technical bottleneck.

[0005] Photoconductive mixers are one type of room-temperature terahertz source. They utilize the optical mixing properties of photoconductive materials to generate stable terahertz waves, potentially replacing photodetectors as noise sources. However, due to the high dielectric constant and thickness of the photoconductive material, its back surface needs to be combined with a silicon lens to achieve terahertz signal radiation into free space. In terahertz devices, rectangular waveguide interfaces are a standard feature, making noise sources with rectangular waveguide outputs more practical in real-world applications. Photoconductive mixers with free-space radiation as their output are clearly unsuitable. Therefore, designing a photoconductive mixer with rectangular waveguide output is an important task. Summary of the Invention

[0006] Therefore, it is necessary to provide a conductivity mixer that can efficiently achieve rectangular waveguide output, which has the characteristics of high structural integration, to address the above-mentioned technical problems.

[0007] To achieve the above-mentioned objectives of this invention, the technical solution adopted is as follows: A rectangular waveguide output photoconductive mixer based on effective dielectric silicon waveguide coupling includes: a photoconductive substrate for exciting charge carriers through the photoconductive effect; a metal planar antenna disposed on a first surface of the photoconductive substrate for converting charge carrier current into a terahertz radiation signal; an effective dielectric silicon waveguide coupled to a second surface and two side surfaces of the photoconductive substrate, the second surface being opposite to the first surface; and a rectangular waveguide for receiving and outputting the terahertz signal; the effective dielectric silicon waveguide includes a waveguide core and an array of air holes distributed on both sides of the waveguide core, the air hole array being configured to create a refractive index gradient in the effective dielectric silicon waveguide to confine the signal for transmission within the waveguide core.

[0008] Preferably, the photoconductive substrate includes a gallium arsenide substrate and a low-temperature gallium arsenide layer grown on the gallium arsenide substrate, and the metal planar antenna is deposited on the low-temperature gallium arsenide layer; the effective dielectric silicon waveguide is fabricated using a high-resistivity floating region silicon wafer and is back-contact coupled to the gallium arsenide substrate.

[0009] Furthermore, the effective dielectric silicon waveguide is provided with a groove structure for accommodating the photoconductive substrate, the photoconductive substrate is embedded in the groove structure, and the size of the groove structure matches the size of the photoconductive substrate.

[0010] Furthermore, the metal planar antenna includes interdigitated electrodes, a wide bowtie antenna, and a bias circuit; wherein the wide bowtie antenna is a linearly polarized antenna; the interdigitated electrodes are located in the central active region of the wide bowtie antenna, and the bias circuit is configured as a bias plate connected to both sides of the wide bowtie antenna.

[0011] Furthermore, the effective dielectric constant of the effective dielectric silicon waveguide is determined based on the Maxwell-Garnett approximation formula, which is: in, The relative permittivity of the effective medium, The relative permittivity of the silicon material constituting the effective dielectric silicon waveguide is given by [reference to a specific material]. is the relative permittivity of air. The air filling factor, the air filling factor Defined as the ratio of the area of ​​the air holes in the air hole array to the total area of ​​the effective dielectric waveguide segment.

[0012] Furthermore, the refractive index of the effective dielectric silicon waveguide satisfy The air filling factor is adjusted by adjusting the radius and spacing of the air holes in the air hole array. This creates a refractive index difference between the waveguide core and the air hole array region.

[0013] Furthermore, the output end of the effective dielectric silicon waveguide extends into a conical transition structure, which extends into the interior of the rectangular waveguide to perform mode conversion on the terahertz radiation signal and couple it into the rectangular waveguide.

[0014] Furthermore, the cross-sectional width of the conical transition structure gradually decreases along the electromagnetic wave propagation direction to make the characteristic impedance change continuously, thereby coupling the signal from the silicon waveguide impedance to the target waveguide impedance of the rectangular waveguide.

[0015] Furthermore, the effective dielectric silicon waveguide 3 is fabricated using a wafer with a relative permittivity similar to that of the photoconductive substrate material. Full-thickness etching is performed on the high-resistivity floating region silicon wafer using deep reactive ion etching technology to form an air hole array 10, a waveguide core 11, and a pointed conical transition structure 12. The air holes in the air hole array are distributed on both sides of the waveguide core in an alternating equidistant arrangement.

[0016] Furthermore, the rectangular waveguide is a WR2.2 standard rectangular waveguide, the outer shell of the rectangular waveguide is made of copper, and the pointed conical transition structure is suspended and positioned within the cavity of the rectangular waveguide to excite the TE10 mode signal.

[0017] The beneficial effects of this invention are as follows: This invention designs a rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling, including a photoconductive substrate, a metal planar antenna, an effective dielectric silicon waveguide, and a rectangular waveguide. It realizes a photoconductive mixer antenna with rectangular waveguide output, which is coupled to a terahertz rectangular waveguide through the effective dielectric silicon waveguide. This overcomes the shortcomings of traditional free space radiation conversion to rectangular waveguide, which requires large space size and is difficult to align. It improves the structural integration and the conversion efficiency of photoconductive mixer antenna to rectangular waveguide. Attached Figure Description

[0018] Figure 1 This is a three-dimensional schematic diagram of a rectangular waveguide output optoconductive mixer based on effective dielectric silicon waveguide coupling; Figure 2 This is a schematic diagram of the metal antenna structure of the photoconductive mixer of the present invention; Figure 3 This is a structural diagram of the photoconductive substrate of the photoconductive mixer of the present invention in one embodiment; Figure 4 This is a top view schematic diagram of the effective dielectric silicon waveguide of the photoconductive mixer of the present invention in one embodiment; Figure 5 This is a schematic diagram of the back-to-back effective dielectric silicon waveguide structure of the photoconductive mixer of the present invention in one embodiment. Figure 6 This is a schematic diagram of a rectangular waveguide back-to-back transmission structure of the effective dielectric silicon waveguide of the photoconductive mixer of the present invention in one embodiment. Figure 7 The diagram shows the electric field distribution of the photoconductive mixer of the present invention in a 412.5 GHz effective dielectric silicon waveguide back-to-back structure in one embodiment. Figure 8 This is a schematic diagram of the back-to-back structure transmission efficiency of the photoconductive mixer of the present invention in one embodiment. Figure 9 The diagram shows the overall structural electric field distribution of the photoconductive mixer of the present invention at 412.5 GHz in one embodiment. Figure 10 This is a schematic diagram illustrating the transmission efficiency of the photoconductive mixer of the present invention in one embodiment.

[0019] In the figure, 1 is a photoconductive substrate, 2 is a metal planar antenna, 3 is an effective dielectric silicon waveguide, 4 is a rectangular waveguide, 5 is a gallium arsenide substrate, 6 is a low-temperature gallium arsenide layer, 7 is an interdigitated electrode, 8 is a wide corded antenna, 9 is a bias circuit, 10 is an air hole array, 11 is a waveguide core, and 12 is a pointed conical transition structure. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] Example 1 like Figure 1 As shown, a rectangular waveguide output photoconductive mixer based on effective dielectric silicon waveguide coupling includes: a photoconductive substrate 1 for exciting carriers through the photoconductive effect; a metal planar antenna 2 disposed on a first surface of the photoconductive substrate 1 for converting carrier current into terahertz radiation signals; an effective dielectric silicon waveguide 3 coupled to a second surface and two sides of the photoconductive substrate 1, the second surface being opposite to the first surface; and a rectangular waveguide 4 for receiving and outputting terahertz signals; the effective dielectric silicon waveguide 3 includes a waveguide core 11 and an air hole array 10 distributed on both sides of the waveguide core 11, the air hole array 10 being configured to create a refractive index gradient in the effective dielectric silicon waveguide 3 to confine the signal transmission within the waveguide core 11.

[0022] Example 2 More specifically, such as Figure 2 As shown, in one specific embodiment, the photoconductive substrate 1 includes a gallium arsenide substrate 5 and a low-temperature gallium arsenide layer 6 grown on the gallium arsenide substrate 5, and the metal planar antenna 2 is deposited on the low-temperature gallium arsenide layer 6; the effective dielectric silicon waveguide 3 is made of a high-resistivity floating region silicon wafer and is back contact coupled to the gallium arsenide substrate 5, and has the characteristics of high carrier mobility, short carrier lifetime and high light absorption efficiency.

[0023] In one specific embodiment, the effective dielectric silicon waveguide 3 is provided with a groove structure for accommodating the photoconductive substrate 1, the photoconductive substrate 1 is embedded in the groove structure, and the size of the groove structure matches the size of the photoconductive substrate 1.

[0024] In this embodiment, the effective dielectric silicon waveguide is fabricated using a wafer with a relative permittivity similar to that of the photoconductive substrate material. Its absorption in the terahertz range is negligible. Full-thickness etching is performed on the high-resistivity floating region silicon wafer using deep reactive ion etching (DEIR) technology to form an air hole array, waveguide core, and a pointed conical transition structure. Through back-coupling with the photoconductive substrate, due to the high permittivity of the gallium arsenide substrate, most of the antenna's radiated signal is transmitted to the substrate. Therefore, utilizing this characteristic, back-coupling from the chip substrate can achieve maximum signal transmission. The staggered, equidistant arrangement of the air holes in the effective dielectric waveguide balances mechanical reliability and refractive index gradient variation. The waveguide core's signal confinement is achieved through the equivalent refractive index difference between the waveguide core and the air hole array.

[0025] In one specific embodiment, the metal planar antenna 2 includes interdigitated electrodes 7, a wide bowtie antenna 8, and a bias circuit 9; wherein, the wide bowtie antenna 8 is a linearly polarized antenna; the interdigitated electrodes 7 are located in the central active region of the wide bowtie antenna 8; the bias circuit 9 is configured as a bias plate connected to both sides of the wide bowtie antenna 8; thereby increasing or decreasing conductivity and increasing the metal-semiconductor contact area. The bowtie antenna can provide broadband characteristics, its input impedance satisfies non-frequency-varying characteristics, and the flatness of the output signal is guaranteed against noise sources.

[0026] In one specific embodiment, the effective dielectric constant of the effective dielectric silicon waveguide 3 is determined based on the Maxwell-Garnett approximation formula, which is: in, The relative permittivity of the effective medium, The relative permittivity of the silicon material constituting the effective dielectric silicon waveguide 3 is given by: is the relative permittivity of air. The air filling factor, the air filling factor Defined as the ratio of the area of ​​the air holes in the air hole array 10 to the total area of ​​the effective dielectric waveguide section.

[0027] In one specific embodiment, the refractive index of the effective dielectric silicon waveguide 3 is... satisfy The air filling factor is adjusted by adjusting the radius G2 and the spacing D1 of the air holes in the air hole array 10. This creates a refractive index difference between the waveguide core 11 and the air hole array 10 region.

[0028] In one specific embodiment, a conical transition structure 12 extends from the output end of the effective dielectric silicon waveguide 3. The conical transition structure 12 extends into the interior of the rectangular waveguide 4 to perform mode conversion on the terahertz radiation signal and couple it into the rectangular waveguide 4. The cross-sectional width of the conical transition structure 12 gradually decreases along the electromagnetic wave propagation direction so that the characteristic impedance changes continuously, coupling the signal from the silicon waveguide impedance to the target waveguide impedance of the rectangular waveguide 4.

[0029] In this embodiment, at the interface between the gallium arsenide substrate and the effective silicon dielectric waveguide, the refractive index is approximately the same, resulting in low signal reflection. When the signal enters the waveguide core of the effective silicon dielectric waveguide, the refractive index difference between the waveguide core and the air hole array region confines it within the waveguide core for transmission. When the signal reaches the conical transition section, the cross-sectional dimensions (width) of the conical transition gradually change along the electromagnetic wave propagation direction, causing the characteristic impedance to change synchronously and continuously. The signal is gradually coupled from the original silicon waveguide impedance to the target waveguide impedance. This further reduces reflections within the rectangular waveguide, enabling the output of the TE10 mode signal from the rectangular waveguide after mode conversion.

[0030] In one specific embodiment, the length L10 of the conical transition structure 12 is set to 1500 μm to achieve impedance matching in the 325-500 GHz frequency band.

[0031] In one specific embodiment, the air holes in the air hole array 10 are distributed on both sides of the waveguide core 11 in an alternating equidistant arrangement; the width W8 of the waveguide core 11 is 230μm.

[0032] In one specific embodiment, the rectangular waveguide 4 is a WR2.2 standard rectangular waveguide with an internal dimension of 285μm×570μm. The outer shell of the rectangular waveguide 4 is made of copper. The pointed cone transition structure 12 is suspended and positioned inside the cavity of the rectangular waveguide 4 to excite the TE10 mode signal.

[0033] Example 3 This embodiment provides a rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling. It mainly consists of four parts: photoconductive substrate 1, metal planar antenna 2, effective dielectric silicon waveguide 3, and rectangular waveguide 4. It aims to achieve efficient generation and transmission of terahertz signals in the 325-500GHz band (WR2.2 band).

[0034] In this embodiment, the specific parameters in the accompanying drawings are shown in Table 1: Table 1 Effective Dielectric Silicon Waveguide Dimensions

[0035] Specifically, such as Figure 3 As shown, the photoconductive substrate 1 of the photoconductive mixer chip design uses a gallium arsenide (GaAs) material system. Specifically, a gallium arsenide substrate 5 with a thickness H1 of 350 μm is selected, and a low-temperature gallium arsenide (LT-GaAs) layer 6 with a thickness H2 of 2 μm is prepared on it through an epitaxial growth process. The low-temperature gallium arsenide layer 6 has high carrier mobility, short carrier lifetime and high light absorption efficiency, making it suitable as an active layer for photoelectric conversion.

[0036] A metal planar antenna 2 is deposited on the upper surface of the low-temperature gallium arsenide layer 6. The antenna material is a titanium / gold (Ti / Au) composite layer with thicknesses H3 of 20 nm and 380 nm, respectively. The antenna structure adopts a wide corded antenna 8 with the fundamental mode polarization direction consistent with that of the rectangular waveguide 4, including a central interdigitated electrode 7, a wide corded antenna radiator 8, and bias circuits 9 on both sides.

[0037] In this embodiment, the specific geometric dimensions of the metal planar antenna are shown in Table 2: Table 2 Dimensions of Metal Planar Bowtie Antennas

[0038] In this embodiment, the opening angle θ of the wide bowtie antenna 8 is 60°; the antenna radiator length L3 is 76μm; the parameters of the interdigitated electrode 7 are: finger length L19μm, finger width W10.2μm, finger gap G11.23μm, and overall region length L218μm; the bias circuit 9 bias plate has a length L672μm and a width W22μm; other auxiliary dimensions are: L4 is 27.6μm, L5 is 14μm, L7 is 150μm, W3 is 2.5μm, and W4 is 45μm.

[0039] In this embodiment, the effective dielectric silicon waveguide 3 is fabricated using a high-resistivity floating region silicon wafer with a thickness of 150 μm. This material exhibits extremely low absorption loss in the terahertz frequency band. An air hole array 10, a silicon waveguide core 11, and a conical transition structure 12 are formed on the silicon wafer through full-thickness etching using deep reactive ion etching (DRIE) technology.

[0040] The effective dielectric silicon waveguide 3 utilizes an air hole array 10 to adjust the equivalent refractive index 16. According to the Maxwell-Garnett approximation theory, by controlling the air filling factor, i.e. the proportion of air hole area, a refractive index difference is formed between the silicon waveguide core 11 and the surrounding medium, thereby confining the terahertz wave within the silicon waveguide core 11 for transmission 17.

[0041] In this embodiment, as Figure 4 As shown, the specific dimensions of the effective dielectric silicon waveguide are as follows: Air hole array 10 design: hole radius G2 is 100μm, hole spacing D1 is 90μm, and silicon waveguide core 11 is arranged in an interleaved and equidistant manner. Width W8: 230μm; Length L9: 2000μm; Length L10: 1500μm of the conical transition structure 12, which ensures a smooth and gradual change in impedance; Overall width W9: 2000μm.

[0042] In addition, in order to achieve compact integration with the photoconductive chip, a groove structure is reserved on the effective dielectric silicon waveguide 3, the width W3 and length L7 of which are matched with the chip size, for embedding the photoconductive substrate 1.

[0043] The rectangular waveguide 4 is designed according to the standard WR2.2 waveguide dimensions, with internal dimensions of 285μm × 570μm and a copper outer shell. The pointed conical transition structure 12 of the effective dielectric silicon waveguide 3 extends suspended into the cavity of the rectangular waveguide 4 to achieve mode conversion.

[0044] The working process of this embodiment is as follows: When a femtosecond laser irradiates the gap between the interdigitated electrodes 7 of the photoconductive substrate 1LT-GaAs layer 6, it excites photogenerated carriers. Under the DC bias voltage provided by the bias circuit 9, the carriers accelerate to form a transient current, which drives the wide bandgap antenna 8 of the metal planar antenna 2 to radiate terahertz waves.

[0045] Because the photoconductive substrate 1 has a high dielectric constant, most of the energy radiated by the metal planar antenna 2 will be transmitted towards the substrate. At this time, the effective dielectric silicon waveguide 3 located on the back of the photoconductive substrate 1 is tightly coupled to the substrate through the groove, extracting the terahertz signal from the substrate and coupling it into the silicon waveguide core 11.

[0046] After the signal enters the silicon waveguide core 11, it is confined by the low-refractive-index air hole array 10 on both sides and propagates forward along the silicon waveguide core 11. When the signal reaches the pointed conical transition structure 12 at the end, the characteristic impedance of the waveguide changes continuously and gradually due to the continuous decrease in cross-sectional width along the propagation direction, thus smoothly matching the signal from the silicon waveguide impedance to the waveguide impedance of the rectangular waveguide 4. Finally, the terahertz wave is efficiently output in the rectangular waveguide 4 in the form of the TE10 mode.

[0047] The above structure was modeled and verified using CST electromagnetic simulation software.

[0048] like Figure 5 , Figure 6 As shown, an effective dielectric silicon waveguide 3 back-to-back test structure is constructed; like Figure 7 As shown, the power transmission efficiency is greater than 95% in the 325-500GHz frequency band, and the electric field energy is effectively confined in the silicon waveguide core 11 at the center frequency of 412.5GHz.

[0049] like Figure 7 , Figure 8 As shown, the complete rectangular waveguide output type optoconductive mixer has a power transmission efficiency of more than 60% in the 325-500GHz range and a fluctuation of less than ±10%, exhibiting excellent flatness.

[0050] like Figure 9 , Figure 10 As shown in the figure, the electric field distribution at 412.5 GHz demonstrates that the terahertz radiation was effectively guided and successfully converted into the fundamental mode TE10 of the rectangular waveguide, verifying the effectiveness of the design.

[0051] In summary, this embodiment overcomes the problems of large size and difficult alignment of traditional free-space radiation schemes by integrating an effective dielectric silicon waveguide, and realizes a compact, high-efficiency, and wide-bandwidth rectangular waveguide output terahertz source.

Claims

1. A rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling, characterized in that, include: Photoconductive substrate (1), which is used to excite carriers through photoconductive effect; A metal planar antenna (2) is disposed on the first surface of the photoconductive substrate (1) for converting carrier current into terahertz radiation signal; an effective dielectric silicon waveguide (3) is coupled to the second surface and two sides of the photoconductive substrate (1), the second surface being opposite to the first surface; and a rectangular waveguide (4) for receiving and outputting terahertz signal; the effective dielectric silicon waveguide (3) includes a waveguide core (11) and an air hole array (10) distributed on both sides of the waveguide core (11), the air hole array (10) being configured to form a refractive index gradient in the effective dielectric silicon waveguide (3) to confine the signal to propagate within the waveguide core (11).

2. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 1, characterized in that, The photoconductive substrate (1) includes a gallium arsenide substrate (5) and a low-temperature gallium arsenide layer (6) grown on the gallium arsenide substrate (5). The metal planar antenna (2) is deposited on the low-temperature gallium arsenide layer (6). The effective dielectric silicon waveguide (3) is made of a high-resistivity floating region silicon wafer and is contact-coupled with the back of the gallium arsenide substrate (5).

3. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 1, characterized in that, The effective dielectric silicon waveguide (3) is provided with a groove structure for accommodating the photoconductive substrate (1), the photoconductive substrate (1) is embedded in the groove structure, and the size of the groove structure matches the size of the photoconductive substrate (1).

4. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 1, characterized in that, The metal planar antenna (2) includes interdigitated electrodes (7), a wide bowtie antenna (8), and a bias circuit (9); wherein the wide bowtie antenna (8) is a linearly polarized antenna; the interdigitated electrodes (7) are located in the central active region of the wide bowtie antenna (8); and the bias circuit (9) is constructed as a bias plate connected to both sides of the wide bowtie antenna (8).

5. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 1, characterized in that, The effective dielectric constant of the effective dielectric silicon waveguide (3) is determined based on the Maxwell-Garnett approximation formula, which is: in, The relative permittivity of the effective medium, The relative permittivity of the silicon material constituting the effective dielectric silicon waveguide (3) is given by: is the relative permittivity of air. The air filling factor, the air filling factor Defined as the ratio of the area of ​​the air holes in the air hole array (10) to the total area of ​​the effective dielectric waveguide segment.

6. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 5, characterized in that, The refractive index of the effective dielectric silicon waveguide (3) satisfy The air filling factor is adjusted by adjusting the radius (G2) and the spacing (D1) of the air holes in the air hole array (10). This creates a refractive index difference between the waveguide core (11) and the air hole array (10) region.

7. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 1, characterized in that, The output end of the effective dielectric silicon waveguide (3) extends into a cone-shaped transition structure (12), which extends into the interior of the rectangular waveguide (4) to perform mode conversion on the terahertz radiation signal and couple it into the rectangular waveguide (4).

8. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 7, characterized in that, The cross-sectional width of the conical transition structure (12) gradually decreases along the electromagnetic wave propagation direction so that the characteristic impedance changes continuously, thereby coupling the signal from the silicon waveguide impedance to the target waveguide impedance of the rectangular waveguide (4).

9. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 7, characterized in that, The effective dielectric silicon waveguide (3) is fabricated using a wafer with a relative permittivity similar to that of the photoconductive substrate material. Full-thickness etching is performed on the high-resistivity floating region silicon wafer using deep reactive ion etching technology to form an air hole array (10), a waveguide core (11), and a cone-shaped transition structure (12). The air holes in the air hole array (10) are distributed on both sides of the waveguide core (11) in an alternating equidistant arrangement.

10. The rectangular waveguide output type photoconductive mixer based on effective dielectric silicon waveguide coupling according to claim 1, characterized in that, The rectangular waveguide (4) is a WR2.2 standard rectangular waveguide. The outer shell of the rectangular waveguide (4) is made of copper. The pointed cone transition structure (12) is suspended and positioned in the cavity of the rectangular waveguide (4) to excite the TE10 mode signal.

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