Vanadium dioxide phase change-based waveguide type terahertz multifunctional filter

Abstract

The utility model belongs to the field of terahertz wave communication equipment, and particularly relates to a waveguide type terahertz multifunctional filter based on vanadium dioxide phase change. The filter comprises a hollow rectangular waveguide resonant cavity, the resonant cavity comprises two parallel and opposite substrates, the substrates are metal substrates or metal films plated on the surfaces of the substrates, the opposite surfaces of the two substrates are provided with periodic fluctuating structures, and the periodic fluctuating structures are formed by alternately arranging protrusions and grooves. The device further comprises a programmable logic device and a voltage controller, the grooves are filled with insulating supporting layers, the surfaces of the insulating supporting layers are plated with vanadium dioxide films, the vanadium dioxide films are electrically connected with the voltage controller, and the voltage controller is electrically connected with the programmable logic device. The programmable logic device carries out phase change control on the vanadium dioxide film through the voltage controller, and the functions of band-stop filtering, single-channel narrow-band filtering, dual-channel narrow-band filtering, band-pass filtering and the like are achieved.

Description

Technical Field

[0001] This utility model belongs to the field of terahertz wave communication equipment, specifically referring to a waveguide-type terahertz multifunctional filter based on vanadium dioxide phase transition. Background Technology

[0002] Terahertz waves (0.1–10 THz), due to their unique spectral location, possess abundant untapped spectral resources and advantages such as high frequency, wide bandwidth, and strong penetration, supporting ultra-high-speed wireless communication. Therefore, they are considered one of the key candidate frequency bands for 6G communication. However, the propagation characteristics of the terahertz band place higher demands on the performance of related devices, especially in terms of the electromagnetic response and dynamic control capabilities of materials. As a key component, terahertz filters play a crucial role in selecting and transmitting specific frequency signals, suppressing interference, and improving system performance, making them an indispensable part of constructing efficient terahertz systems. However, traditional materials, limited by their inherent electromagnetic properties, struggle to achieve precise control and reconfigurable filtering functions for terahertz waves. Therefore, developing programmable terahertz filters based on novel functional materials and structures has become a current research hotspot and challenge. Currently, researchers have extensively explored combining artificial structures such as metamaterials, metasurfaces, and photonic crystals with phase change materials such as liquid crystals, graphene, and vanadium dioxide to design various tunable terahertz filter devices, providing new means for the effective control of terahertz waves. For example, in 2023, Hao et al. proposed an all-dielectric non-metallic metamaterial terahertz filter device, achieving high-efficiency modulation over a wide frequency range. In 2024, Tian et al. developed a tunable bandstop fiber optic filter based on laser-induced graphene metamaterials, with an operating frequency span of 269 GHz and a tunable range of 21 GHz. In the same year, Yu et al. utilized quasi-bound metasurfaces coupled with nematic liquid crystals to achieve tunable filtering with high Q-value and narrow bandwidth in the near-infrared range. Although research on multifunctional terahertz filters is increasingly in-depth, their application in waveguides is still limited. Utility Model Content

[0003] The purpose of this invention is to provide a waveguide-type terahertz multifunctional filter based on vanadium dioxide phase transition that is simple in structure, low in cost, small in size and easy to integrate.

[0004] The technical solutions for achieving the above objectives include the following:

[0005] A waveguide-type terahertz multifunctional filter based on vanadium dioxide phase transition includes a hollow rectangular waveguide resonant cavity. The resonant cavity includes two parallel and opposite substrates, which are metal substrates or have a metal thin film coated on their surface. The opposite surfaces of the two substrates have a periodic undulating structure, which is composed of alternating protrusions and grooves. The filter also includes a programmable logic device and a voltage controller. Each groove is filled with an insulating support layer, and the surface of the insulating support layer is coated with a vanadium dioxide thin film. The vanadium dioxide thin film is electrically connected to the voltage controller, and the voltage controller is electrically connected to the programmable logic device. During operation, the programmable logic device controls the phase transition of the vanadium dioxide thin film through the voltage controller.

[0006] Furthermore, the insulating support layer is made of polyimide, which is a material with high terahertz wave transmittance, which is beneficial for the bottom wall of the groove to reflect electromagnetic waves.

[0007] Furthermore, the polyimide is filled into the groove by spin coating.

[0008] Furthermore, the programmable logic device is a field-programmable gate array (FPGA).

[0009] Furthermore, the number of periods N in the periodic undulation structure is not less than 11. The number of periods N is related to the function being implemented. If the period is too large, it will easily lead to an increase in device size, which is not conducive to integration and the cost will be too high. If the number of periods N is too small, it will be impossible to guarantee a high-quality filtering effect.

[0010] Furthermore, the vanadium dioxide thin film is deposited on the surface of the insulating support layer using magnetron sputtering technology.

[0011] Furthermore, the substrate material is silicon.

[0012] The above-mentioned method of using a multifunctional filter includes the following steps: terahertz waves enter the waveguide resonant cavity; a programmable logic device controls a voltage amplifier to apply an external excitation voltage to vanadium dioxide in different regions, thereby inducing an insulating-metal phase transition. When vanadium dioxide is in the insulating phase, the terahertz waves will be incident inside the groove, and the unit structure is equivalent to a groove, i.e., "0"; when it is in the metallic phase, the terahertz waves are reflected, and the unit structure is equivalent to a protrusion, i.e., "1"; the encoding control of the vanadium dioxide thin film is realized to obtain waveguides with different encoding structures, including periodic waveguides, single-defect waveguides, double-defect waveguides, and straight waveguides, thereby realizing band-stop filtering, single-channel narrowband filtering, dual-channel narrowband filtering, and bandpass filtering functions.

[0013] This invention relates to a waveguide-type terahertz multifunctional filter based on vanadium dioxide phase transition. The substrate can be made of a low-loss metallic material in the terahertz band (such as gold, silver, copper, aluminum alloy, etc.), or it can be made of non-metallic materials (such as silicon wafers, acrylic sheets, or resin, etc.) with a thin metal film deposited on its surface. The material of the metal film is gold, silver, or copper, and its thickness can be designed according to the skin depth of the selected metal in the filtering band. The periodic undulation structure, the geometry of the protrusions and grooves can be rectangular, trapezoidal, triangular, sine, cosine, etc., and can be flexibly set according to application requirements. The structural parameters of the substrate waveguide, including the period length Λ, the depth ξ of the protrusions and grooves, the distance d between the two plates, etc., can all be optimized according to the target terahertz operating frequency band and application scenario to meet the filtering requirements of different frequencies and bandwidths. The number of periods N of the periodic undulation structure is related to the function to be achieved. Too large a period will easily lead to an increase in device size, which is not conducive to integration and is too costly; too low a period cannot guarantee a high-quality filtering effect. Those skilled in the art can determine the appropriate number of periods N according to the filtering quality.

[0014] This invention relates to a waveguide-type terahertz multifunctional filter based on vanadium dioxide phase transition. By adjusting the external excitation voltage, the conductivity of vanadium dioxide on polyimide in different grooves is varied, resulting in waveguides with different coding structures, including periodic waveguides, single-defect waveguides, double-defect waveguides, and straight waveguides. These equivalent waveguide structures can respectively achieve band-stop filtering, single-channel narrowband filtering, dual-channel narrowband filtering, and bandpass filtering functions. By setting different substrate structure parameters, this multifunctional filter can achieve multifunctional tuning for selective transmission of signals in specific frequency bands, solving the problems of single filtering function, high power consumption, and complex fabrication processes in existing waveguide-type filter technology.

[0015] Compared with the prior art, the technical solution of this utility model has the following beneficial technical effects:

[0016] 1. This utility model has the advantages of simple structure, miniaturization, low cost, easy integration with other terahertz components or systems, and convenient practical application and large-scale manufacturing.

[0017] 2. This utility model has diverse functions and selectively transmits terahertz signals in different frequency bands, significantly improving the applicability and flexibility of the filter.

[0018] 3. This utility model utilizes programmable logic devices to precisely control the external excitation voltage, thereby realizing real-time dynamic switching of the waveguide coding structure, which has the advantages of flexible control and reconfigurability.

[0019] 4. This utility model features high performance and wide adaptability. By optimizing the period length, depth, and material selection of the flat plate undulation structure, the operating frequency and bandwidth of the filter can be precisely controlled to meet the stringent performance requirements of different application scenarios. Attached Figure Description

[0020] Figure 1 A schematic diagram of a waveguide-type terahertz multifunctional filter structure based on vanadium dioxide phase transition, as shown in the embodiment;

[0021] Figure 2 This is a front view of the hollow rectangular waveguide resonant cavity in the embodiment.

[0022] Figure 3 The terahertz wave transmission spectra of the filter used in this embodiment under different coding sequences are shown.

[0023] In the figure, a is the bandpass filter spectrum, b is the bandstop filter spectrum, c is the single-channel filter spectrum, and d is the dual-channel filter spectrum. 1. Gold film; 2. Silicon substrate; 3. Polyimide; 4. Vanadium dioxide thin film; 5. PCB circuit board; 21. Terahertz wave inlet; 22. Terahertz wave outlet. Detailed Implementation

[0024] The present invention will be described in detail below with reference to the embodiments.

[0025] See Figures 1 to 2A waveguide-type terahertz multifunctional filter based on vanadium dioxide phase transition includes a hollow rectangular waveguide resonant cavity, a programmable gate array (FPGA) chip, and a voltage amplifier. The resonant cavity includes two parallel silicon plates 2, whose opposing surfaces have a periodic undulating structure. The undulating structure is composed of multiple rectangular protrusions and grooves arranged alternately at intervals. In this embodiment, the protrusions are defined as "1" and the grooves are defined as "0" to achieve digital encoding of the waveguide structure. Adjacent protrusions and grooves form a period. A gold film 1 is deposited on the surface of the plate with the undulating structure to reduce energy loss during terahertz wave propagation. The deposition is performed by ion sputtering, and the thickness is optimized according to the skin depth of the selected material in the corresponding filtering band. Each groove is filled with polyimide 3 as a support frame by spin coating. After the polyimide 3 is cured, a monoclinic vanadium dioxide thin film 4 is deposited on its surface using magnetron sputtering. The undulating structural surfaces of the two silicon substrates 2 are placed opposite each other to form a waveguide structure with a hollow rectangular cross-section. The silicon substrate 2 of the waveguide is integrated into the PCB circuit board 5. The vanadium dioxide thin film 4 in each groove is electrically connected to the voltage amplifier, which is electrically connected to the programmable gate array (FPGA) chip. The structural dimensions of the waveguide of the silicon substrate 2 in this embodiment are: period length Λ = 200 μm, undulation parameter ξ = 25 μm, distance between the two silicon substrates d = 180 μm, and number of periods N = 15.

[0026] When this multifunctional filter is in operation, terahertz waves enter the waveguide through the inlet 21 and exit through the outlet 22. An external excitation voltage is applied to the vanadium dioxide thin film in different strip regions by a voltage amplifier controlled by a field-programmable gate array (FPGA), inducing an insulating-metal phase transition and achieving controllable adjustment of the vanadium dioxide conductivity. When the vanadium dioxide thin film is in the insulating phase, the terahertz waves are incident inside the groove, and the unit structure is equivalent to a groove, i.e., "0"; when it is in the metallic phase, the terahertz waves are reflected, and the unit structure is equivalent to a protrusion, i.e., "1". Through encoding control of the vanadium dioxide thin film, different structures such as periodic waveguides, single-defect waveguides, double-defect waveguides, and straight waveguides can be realized, thereby achieving functions such as band-stop filtering, single-channel narrowband filtering, dual-channel narrowband filtering, and bandpass filtering. This novel terahertz multifunctional filter has a simple structure, small size, low cost, and is easy to integrate. It is programmable through the voltage applied by the FPGA, making it simple to operate and flexibly adjustable.

[0027] Figure 3 The terahertz transmission spectra under different coding sequences are shown:

[0028] When the encoded sequence is “1111111111111111111111111111111111”, corresponding to a straight waveguide, it exhibits bandpass filtering functionality. (See...) Figure 3 (a);

[0029] When the encoded sequence is “1010101010101010101010101010101”, it is a periodic waveguide, which excites Bragg resonance to achieve band-stop filtering. The bandgap frequency range is 1.019-1.119 THz. (See [link to relevant documentation]). Figure 3 (b);

[0030] When the encoded sequence is “1010101010101011101010101010101”, it is equivalent to a single-defect waveguide. Due to the localization caused by the defect structure, a narrow-band transmission peak is excited within the bandgap, realizing a single-channel filtering function. The bandgap frequency range is 0.995-1.121 THz, and the transmission peak frequency position is f=1.033 THz. See [link to relevant documentation]. Figure 3 (c);

[0031] When the encoded sequence is "1010101011101010101110101010101", it is a double-defect waveguide. Due to the two localizations caused by the defect structure, two narrowband transmission peaks are excited within the bandgap, realizing the dual-channel filtering function. The bandgap frequency range is 0.967-1.121 THz, and the frequency positions of the two transmission peaks are f1=1.015 THz and f2=1.038 THz, see [link to relevant documentation]. Figure 3 (d).

[0032] In summary, this waveguide-based terahertz multifunctional filter, based on vanadium dioxide phase transition, features a simple structure, compact size, and convenient fabrication, making it easy to integrate into terahertz systems. By dynamically adjusting the vanadium dioxide phase transition state using an external voltage, the waveguide coding structure can be flexibly modified to achieve a multifunctional filtering response. Parameters such as the number of periods, period length, ripple depth, and plate spacing on the flat plate can be designed according to actual needs, demonstrating good controllability and broad application prospects.

Claims

1. A waveguide-type terahertz multifunctional filter based on vanadium dioxide phase transition, comprising a hollow rectangular waveguide resonant cavity, the resonant cavity comprising two parallel and opposite substrates, the substrates being metal substrates or having a metal thin film coated on their surface, the opposite surfaces of the two substrates having a periodic undulating structure, the periodic undulating structure being composed of alternating protrusions and grooves, characterized in that, It also includes a programmable logic device and a voltage controller. Each groove is filled with an insulating support layer, and the surface of the insulating support layer is coated with a vanadium dioxide film. The vanadium dioxide film is electrically connected to the voltage controller, and the voltage controller is electrically connected to the programmable logic device. During operation, the programmable logic device performs phase change control on the vanadium dioxide film through the voltage controller.

2. The waveguide-type terahertz multi-functional filter based on phase change of vanadium dioxide according to claim 1, characterized in that, The insulating support layer is made of polyimide. 3.The waveguide-type terahertz multi-functional filter based on vanadium dioxide phase transition according to claim 2, characterized in that, The polyimide is filled into the groove by spin coating.

4. The waveguide-type terahertz multi-functional filter based on phase change of vanadium dioxide according to claim 1, characterized in that, The programmable logic device is a Field Programmable Gate Array (FPGA).

5. The waveguide-type terahertz multi-functional filter based on phase change of vanadium dioxide according to claim 1, characterized in that, The number of periods N in the periodic undulation structure is not less than 11. 6.The waveguide-type terahertz multi-functional filter based on vanadium dioxide phase transition according to claim 1, wherein, The vanadium dioxide thin film is deposited on the surface of the insulating support layer by magnetron sputtering. 7.The waveguide-type terahertz multi-functional filter based on phase change of vanadium dioxide according to claim 1, wherein The substrate is made of silicon.

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