Double-line waveguide polarization rotator model design method

Abstract

The invention belongs to the technical field of millimeter wave photoelectric devices, and particularly relates to a double-line waveguide polarization rotator model design method. The method comprises the following steps: collecting polarization rotation parameters including a target rotation angle, a working frequency band and an insertion loss requirement; the method comprises the steps that simulation software is used for building a geometric model, simulating metal wires and multiple dielectric layers sequentially surrounding from inside to outside, a double-wire waveguide basic model is built, the two metal wires are parallel and not coplanar and form a waveguide structure, ports are set as optical signal input and output ends, the rotation angle and the optimal length of the metal wires are adjusted, and a three-dimensional simulation model is built; after mode analysis verification, a model entity is obtained through 3D printing, the polarization state and the polarization extinction ratio are tested, and the performance is evaluated; and finally, iterative optimization is carried out until the optimal rotation angle is obtained. The method supports flexible regulation and control of the polarization rotation angle, the influence of external factors on the performance is small, efficient and accurate control over the light polarization state can be achieved, and the method is suitable for the fields of terahertz communication, imaging and the like.

Description

Technical Field

[0001] This invention belongs to the field of millimeter-wave optoelectronic device technology, specifically relating to a design method for a dual-wire waveguide polarization rotator model. Background Technology

[0002] Terahertz waves, as a key band in the electromagnetic spectrum between microwaves and infrared, show great potential for applications in high-speed communication, non-destructive imaging, biosensing, and security detection. For example, in terahertz communication systems, precise control of polarization states can effectively improve signal anti-interference capabilities and data transmission rates; in bioimaging, polarization rotators can be used to enhance tissue contrast and improve diagnostic accuracy. As a core component of terahertz optoelectronic devices, the dual-wire waveguide polarization rotator guides and modulates light wave polarization through a dual-metallic wire structure, offering advantages such as compact structure and high integration. Its design quality directly determines the performance and reliability of the terahertz system. Therefore, developing efficient and stable dual-wire waveguide polarization rotator models is crucial for promoting the practical application of terahertz technology.

[0003] Currently, the design methods for existing dual-wire waveguide polarization rotator models mainly rely on empirical adjustments and simplified simulation processes. Common practices include: preliminary modeling based on traditional waveguide theory by manually setting the geometric parameters of the metal wires (such as spacing and diameter); static simulation using finite element software (such as COMSOL) to estimate the polarization rotation effect; and fabricating prototypes using standard photolithography or micromachining techniques, optimizing performance through repeated trial and error. However, these methods suffer from low polarization control accuracy, are difficult to adapt to specific application scenarios, and often exhibit rotation angle deviations exceeding 10%, failing to meet the requirements for low-loss, wide-bandwidth, and high-precision imaging. Furthermore, existing technologies rely on complex micromachining processes, such as electron beam lithography, in the fabrication of dual-wire waveguide polarization rotator models, resulting in long cycles, poor environmental adaptability, and performance susceptibility to temperature fluctuations. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a design method for a dual-waveguide polarization rotator model. This method simplifies the manufacturing process and improves environmental stability through modular design, resulting in a device with advantages such as high integration, low loss, and wide bandwidth.

[0005] The technical solution of this invention is: A design method for a dual-wire waveguide polarization rotator model includes the following steps: Acquire the polarization rotation parameters of the terahertz guided wave, including the target rotation angle, operating frequency band, and insertion loss requirements; Based on the polarization rotation parameters, a geometric shape is constructed using simulation software to form a double-wire waveguide structure. The double-wire waveguide structure includes two parallel and non-coplanar metal wires and a multilayer dielectric layer that is sequentially wrapped around the outside of the metal wires from the inside out. The two ends of the metal wires are respectively set as optical signal input ports and optical signal output ports. Based on the polarization rotation parameters and the dual-wire waveguide structure, the rotation angle and optimal length of the two metal wires in the adjacent dielectric layer are adjusted to build a three-dimensional simulation model of the polarization rotator. The constructed 3D simulation model was 3D printed to obtain the physical model of the dual-line waveguide polarization rotator. A light source is coupled from the dual-waveguide polarization rotator model entity to two metal wires via optical fiber and connected to the optical signal input end of the metal wires. A photodetector is connected to the optical signal output end of the metal wires to obtain the polarization state and polarization extinction ratio of the dual-waveguide polarization rotator model entity under different optical signals. Based on the polarization extinction ratio, evaluate the quality performance of the dual-wire waveguide polarization rotator model entity under the current polarization state. Based on the quality performance evaluation results, repeat the above steps, record the rotation angles of the two metal lines corresponding to different polarization states, and obtain the optical signal transmission efficiency and loss index under different polarization states through a photodetector. Compare with the preset values ​​to obtain the rotation angles of the two metal lines under the optimal polarization state, and complete the final design of the dual-wire waveguide polarization rotator model.

[0006] Preferably, the polarization extinction ratio is determined according to the following formula: PER=10 ), Where PER is the polarization extinction ratio. For the maximum polarized light intensity, This represents the minimum polarized light intensity.

[0007] Preferably, the quality performance of the dual-waveguide polarization rotator model entity under the current polarization state is determined according to the following formula: PER≥A Where PER is the polarization extinction ratio and A is the optimal extinction ratio.

[0008] Preferably, the first, third, and fourth dielectric layers are all air, and the second dielectric layer is made of resin.

[0009] Preferably, the dielectric layer includes at least a first dielectric layer, a second dielectric layer, a third dielectric layer, and a fourth dielectric layer, wherein the first dielectric layer, the third dielectric layer, and the fourth dielectric layer are all air, and there is a gap between the third dielectric layer and the fourth dielectric layer, and the second dielectric layer is made of resin material.

[0010] Preferably, the shape of the metal wire includes, but is not limited to, a cylindrical shape, and the bilinear waveguide structure formed by two metal wires includes, but is not limited to, a bicolumnar structure.

[0011] Preferably, the two metal wires have a double helix structure, and the helix twist angle of the metal wires is [0, 2π].

[0012] Preferably, the optimal length of the two metal wires is determined as follows: The rotation angles of the two metal wires are determined, and the length of the metal wires is scanned using simulation software to obtain the scattering parameters of the metal wires at different lengths. The scattering parameters include return loss and insertion loss. Based on the length transformation of the metal wires, the maximum difference between the return loss and insertion loss is obtained. The metal wire length corresponding to the maximum difference is the required optimal metal wire length.

[0013] Compared with the prior art, the dual-waveguide polarization rotator model design method of the present invention has the following advantages: This invention first collects polarization rotation parameters such as target rotation angle, operating frequency band, and insertion loss to provide precise input for model construction, directly addressing the lack of initial requirements analysis in traditional designs. Then, it utilizes simulation software to build a basic model based on a bilinear waveguide structure, and constructs a three-dimensional simulation model by adjusting the rotation angle and optimal length of the metal wire, ensuring precise control of the geometric shape and thus solving the defect of insufficient polarization rotation accuracy. Next, it combines 3D printing technology to rapidly manufacture the model entity, and iteratively evaluates performance by testing the polarization extinction ratio using fiber coupling and photodetectors. This closed-loop testing mechanism optimizes insertion loss and operating frequency band. The modular design of the above methods simplifies the manufacturing process, improves environmental stability, and enables the final device to possess advantages such as high integration, low loss, and wide bandwidth. Attached Figure Description

[0014] Figure 1 A flowchart illustrating the design method of an embodiment of the present invention; Figure 2 This is a front view of the COMSOL simulation model according to an embodiment of the present invention; Figure 3 This is a three-dimensional transparent view of the polarization rotator according to an embodiment of the present invention; Figure 4 This is a length scan result diagram of an embodiment of the present invention; Figure 5 This is a SOLIDWORKS model diagram with a rotation angle of 90° according to an embodiment of the present invention; Figure 6 This is a SOLIDWORKS model diagram with a rotation angle of 90° according to an embodiment of the present invention; Figure 7This is a SOLIDWORKS model diagram with a rotation angle of 90° according to an embodiment of the present invention; Figure 8 This is a 3D printed physical image of an embodiment of the present invention; Figure 9 This is a graph showing the relationship between polarization extinction ratio and guided wave frequency in an embodiment of the present invention.

[0015] Explanation of reference numerals in the attached figures: 1. Metal wire; 2. First dielectric layer; 3. Second dielectric layer; 4. Third dielectric layer; 5. Fourth dielectric layer. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0018] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0019] See Figures 1 to 9 As shown, in order to simplify the manufacturing process, improve environmental stability, and enable the final device to have advantages such as high integration, low loss, and wide bandwidth, this embodiment provides a design method for a dual-wire waveguide polarization rotator model, including the following steps: S1. Acquire the polarization rotation parameters of the terahertz guided wave, including the target rotation angle, operating frequency band, and insertion loss requirements; S2. Based on the polarization rotation parameters, a geometric shape is constructed using simulation software. The metal wire and the first, second, third, and fourth dielectric layers sequentially surrounding the metal wire from the inside out are used as model combination objects to establish a basic model of a dual-wire waveguide polarization rotator. The metal wire is configured as two parallel and non-coplanar lines located within the first dielectric layer, thus forming a dual-wire waveguide structure. The two ends of the metal wire are respectively configured as an optical signal input port and an optical signal output port. S3. Based on the polarization rotation parameters and the dual-wire waveguide structure, adjust the rotation angle and optimal length of the two metal wires in the first dielectric layer to build a three-dimensional simulation model of the polarization rotator. S4. After performing pattern analysis using simulation software and confirming that the constructed 3D simulation model is correct, 3D print the constructed 3D simulation model to obtain the physical model of the dual-line waveguide polarization rotator. S5. Couple the light source from the optical signal input end of the dual-waveguide polarization rotator model entity to two metal wires through an optical fiber, and connect a photodetector at the optical signal output end to obtain the polarization state and polarization extinction ratio of the model entity under different optical signals. S6. Based on the polarization extinction ratio, evaluate the quality performance of the dual-waveguide polarization rotator model entity under the current polarization state; S7. Based on the quality performance evaluation results, repeat steps S2 to S6, record the rotation angles of the two metal lines corresponding to different polarization states, and obtain the optical signal transmission efficiency and loss index through a photodetector. Compare them to obtain the rotation angles of the two metal lines under the optimal polarization state, and complete the final design of the dual-wire waveguide polarization rotator model.

[0020] Specifically: Step S1: Acquire the polarization rotation parameters of the terahertz guided wave In terahertz communication systems, the target rotation angle may be 90° to achieve quadrature modulation of the signal; the operating frequency band needs to cover 0.1THz~10THz; and the insertion loss requirement is usually less than 2dB.

[0021] Parameter acquisition must be based on actual applications, including: Target rotation angle: determined through theoretical calculation or pre-simulation. For example, if a linear polarization rotation of 90° is required, the target angle is set to 90°.

[0022] Operating frequency band: determined based on the bandwidth of the terahertz system; for example, broadband applications require coverage of 1-5 THz.

[0023] Insertion loss requirement: Referring to industry standards, it is typically required to be below 2 dB to ensure transmission efficiency.

[0024] This step provides input for subsequent design, avoids the blind spots of traditional design, and ensures polarization control accuracy.

[0025] Step S2: Construct the basic model of the dual-wire waveguide polarization rotator See Figure 2 As shown, the COMSOL Multiphysics software is used to access the 3D model interface and construct the geometry. The model assembly includes a metal wire, a first dielectric layer, a second dielectric layer, a third dielectric layer, and a fourth dielectric layer.

[0026] The metal wire 1 configuration consists of two metal wires placed within the first dielectric layer, initially parallel but not coplanar, forming a bilinear waveguide structure. The metal wire material can be copper or silver, and the diameter is set to a subwavelength scale (e.g., 100 μm) to support terahertz surface plasmon waves.

[0027] Dielectric layer distribution: The first dielectric layer 2, the second dielectric layer 3, the third dielectric layer 4, and the fourth dielectric layer 5 are distributed sequentially from the inside out in a ring-shaped cross-section, with their axes coinciding. Specific materials:

[0028] First dielectric layer 2: Air (refractive index ≈ 1), used to reduce light wave absorption.

[0029] Second dielectric layer 3: resin (refractive index ≈ 1.5), providing mechanical support.

[0030] The third dielectric layer 4 and the fourth dielectric layer 5: air or a specific gas (such as helium) are used to simulate the scattering environment.

[0031] Port settings: The two ends of metal wire 1 are defined as optical signal input port and output port, respectively, for setting boundary conditions in simulation.

[0032] When modeling, geometric accuracy must be ensured. For example, in COMSOL, the "Geometry" module is used to draw a ring-shaped layered structure, and properties are assigned through the "Material" module.

[0033] Figure 2 This is a front view of the COMSOL simulation model according to an embodiment of the present invention. In the figure: 1 represents a metal wire, which affects the polarization of light waves by applying an electromagnetic field; 2 represents an air layer, which reduces absorption and scattering; 3 represents a resin layer, which provides refractive index guidance and mechanical support; 4 and 5 are air layers, simulating the external environment. This figure shows the structure of the basic model and provides a visual reference for step S2.

[0034] Step S3: Adjust parameters and build a 3D simulation model Based on the parameters acquired by S1, adjust the rotation angle and optimal length of the two metal wires: Rotation Angle Adjustment: In COMSOL, the rotation angle of the metal wire along the axial direction (between 0 and 2π) can be changed using the parametric scan function. For example, if the target rotation angle is 90°, then set the rotation angle to 90°. The rotation angle directly affects the polarization state change and needs to be verified through electric field distribution simulation.

[0035] Determining the optimal length: Length scanning is performed using COMSOL's pattern analysis module.

[0036] Specific steps: Set the metal wire length variable (e.g., from 0.5 cm to 2.0 cm). Calculate the scattering parameters S11 (return loss) and S21 (insertion loss). Plot the curves of S11 and S21 as a function of length, and find the length corresponding to the point of maximum difference as the optimal length.

[0037] 3D Model Construction: Import the optimized parameters into SOLIDWORKS to build a 3D simulation model. The model needs to include details such as the twisted metal wire structure (which can be in a double helix shape) and the dielectric layer interface.

[0038] like Figure 3 As shown, this step ensures precise control of the geometry and solves the problem of polarization rotation accuracy. Figure 3 This is a three-dimensional transparent image of the polarization rotator according to an embodiment of the present invention, showing the electric field distribution of the terahertz surface plasmon wave. This image corresponds to the simulation verification in step S3, helping to intuitively understand the polarization rotation effect.

[0039] Figures 5 to 7 This is a SOLIDWORKS model diagram with a rotation angle of 90° according to an embodiment of the present invention. The metal line 1 in the diagram is spirally twisted, and the dielectric layer structure is clear, providing a reference for the construction of the 3D model.

[0040] Step S4: Pattern Analysis and 3D Printing Perform pattern analysis in COMSOL to validate the model: Mode Analysis: Use the "Electromagnetic Wave Frequency Domain" module to calculate the electric and magnetic field distributions of the guided wave mode. Check parameters such as transmission efficiency to ensure they meet specifications (e.g., S21 > -2 dB). If the model is incorrect, return to S3 for adjustment.

[0041] 3D Printing: After verification, the SOLIDWORKS model is exported as an STL file, and a high-precision 3D printer (such as a photopolymer printer) is used to create the physical object. Material Selection: Resin body, using photosensitive resin, ensuring refractive index matching. Metal Wires: A silver layer is deposited on the resin surface through electroplating or sputtering to form a conductive structure.

[0042] Post-processing: If necessary, polishing or coating may be performed to reduce surface roughness.

[0043] This step enables rapid prototyping, reducing the cost and difficulty of traditional micromachining. Figure 7 The 3D printed object is shown. The metal line 1 in the image is achieved through silver plating, and the resin layer provides support, reflecting the manufacturing result of step S4.

[0044] Step S5: Test polarization state Integrating entity models into the testing system: Source coupling: A terahertz source (such as a quantum cascade laser) is coupled to the input port via optical fiber. Precise alignment is required to minimize insertion loss.

[0045] Polarization state measurement: Connect a photodetector (such as a terahertz detector) to the output terminal and measure the output light intensity. Obtain the maximum and minimum light intensities P by rotating the polarizer. max and P min .

[0046] Data acquisition: Record the output under different input polarization states to calculate the polarization extinction ratio.

[0047] Step S6: Evaluate quality performance Based on the S5 data, calculate the polarization extinction ratio (PER): PER=10 ), Where PER is the polarization extinction ratio. For the maximum polarized light intensity, Minimum polarized light intensity For example, if P max =1.0mW, P min =0.01mW, then PER=20dB.

[0048] Performance evaluation: PER ≥ A, where A ≥ 40 dB. If the measured PER is below 40 dB, the performance is considered substandard and requires optimization.

[0049] This step ensures quantitative assessment and avoids subjective judgment.

[0050] Step S7: Iterative Optimization Based on the results of S6, repeat S2-S6: Parameter adjustment: For example, if PER is insufficient, the wire spacing or rotation angle can be adjusted.

[0051] Data recording: Record the rotation angle, transmission efficiency (S21), and loss index for each iteration.

[0052] Optimization objective: Find the optimal combination of parameters that maximizes PER. This typically requires 3-5 iterations.

[0053] This closed-loop process solves the problem of lack of system optimization in traditional design. Figure 3 This is a length scan result diagram of an embodiment of the present invention, showing the relationship between S11 and S21 and the waveguide length. This diagram is used for optimization analysis in steps S3 and S7 to help determine the optimal length.

[0054] Figure 4In this diagram, S11 represents return loss, which is the ratio of reflected power to input power when a signal is input from one port. A smaller S11 value indicates less reflected energy, meaning a better match between the input port and the signal source. S21 represents insertion loss or gain, describing the transmission efficiency when an electromagnetic wave inputs from port 1 and outputs from port 2. A larger S21 value indicates less loss of the optical signal as it passes through the device, resulting in higher transmission efficiency.

[0055] The optimal waveguide length to be determined is the length corresponding to the maximum difference between S11 and S21, to ensure that the designed waveguide can effectively support the required polarization mode.

[0056] Furthermore, polarization extinction ratio PER=10 ), Where PER is the polarization extinction ratio. For the maximum polarized light intensity, Minimum polarized light intensity For example, if P max =1.0mW, P min =0.01mW, then PER=20dB.

[0057] This is the core of evaluating the polarization rotation effect. During the testing phase (step S5), measurement accuracy must be ensured.

[0058] Measurement equipment: Use a calibrated optical power meter with a sampling rate of not less than 1 kHz to reduce noise.

[0059] Operating procedure: Fix the input polarization state, rotate the output polarizer, and record the extreme values ​​of light intensity. For example, with a target rotated 90°, if the input is linearly polarized light, the output should be orthogonally polarized, and ideally, Pmin should be close to zero.

[0060] Error handling: Take the average of multiple measurements to eliminate the influence of environmental fluctuations.

[0061] Furthermore, quality performance evaluation standards A standard PER ≥ A (A ≥ 40 dB) ensures high device performance. In implementation:

[0062] Threshold setting: The value of A can be adjusted according to the application. For example, high-precision sensing requires A ≥ 40 dB, while communication systems can relax it to 30 dB.

[0063] Verification method: If the measured PER is 35 dB, it can be improved to 40 dB by optimizing the surface roughness of the metal wire or the dielectric layer material (such as changing to a low-loss resin).

[0064] Example Description: In this embodiment, through optimization, the PER was improved from an initial 30 dB to 45 dB. This limitation is directly related to the iterative optimization step S7.

[0065] Furthermore, dielectric layer materials and structures Material selection: The first, third, and fourth dielectric layers are air, and the second dielectric layer is resin. The air layer has a low refractive index (≈1), reducing light scattering; the resin layer (such as epoxy resin) has a refractive index ≈1.5, providing mechanical stability.

[0066] When modeling, material properties must be correctly defined in COMSOL.

[0067] Structural Distribution: The dielectric layers are distributed in a ring-shaped pattern with coincident axes. In SOLIDWORKS, the concentric rings are drawn using the "Rotation" feature to ensure geometric symmetry. This structure optimizes waveguide mode matching and reduces insertion loss. Figure 2 and Figure 3 The dielectric layer structure is shown.

[0068] Furthermore, the shape of the metal wire The shape of the metal wire can be cylindrical, elliptical, or rectangular. Cylindrical is the most common, with a diameter of 100 μm; elliptical can be used to enhance polarization sensitivity, with a major-to-minor axis ratio of 2:1.

[0069] In COMSOL, shapes are defined using parametric curves. This flexibility supports different scenario requirements, such as the ease of manufacturing rectangular cross-sections.

[0070] Furthermore, the bimetallic wire should preferably adopt a double-helix twisted structure with a twist angle of 0 to 2π. For example, a 90° rotation corresponds to a twist angle of π / 2.

[0071] During modeling, the "spiral" tool in SOLIDWORKS is used to generate the path, which is then scanned to create the solid. The spiral structure improves polarization rotation efficiency and reduces mode coupling loss. Figure 4 An example of spiral twisting is shown.

[0072] Furthermore, the method for determining the optimal length of the metal wire. The methods include length scanning and scattering parameter analysis: Scan settings: In COMSOL, set the length variable L to a range of 0.5-2.0 cm and a step size of 0.1 cm.

[0073] Parameter extraction: Simulation calculation of S11 and S21. The smaller S11 is, the less reflection there is, and the larger S21 is, the higher the transmission efficiency.

[0074] Difference analysis: Plot the Lvs.|S21 - S11| curve; the peak value corresponds to the optimal length. For example, Figure 4 The difference is largest at 1.2 cm, therefore the optimal length is 1.2 cm. This method ensures optimized waveguide length, supporting the requirement for low insertion loss.

[0075] Taking a 90° rotation as an example, a specific embodiment is described in detail to achieve a 90° polarization rotation. The embodiment, together with the accompanying drawings, explains the operation process step by step.

[0076] Initial settings Target parameters (S1): rotation angle 90°, operating frequency band 1THz~3THz, insertion loss <2 dB.

[0077] Software tools: COMSOL 5.6 and SOLIDWORKS 2022.

[0078] Step 1: Build the COMSOL model Open COMSOL and select "3D Model".

[0079] Geometry drawing: First, create two parallel metal lines (cylindrical, 100 μm in diameter) and place them inside the first air layer (radius 200 μm). Then add a resin layer (50 μm thick) and an outer air layer.

[0080] Material allocation: The metal wire is set to silver (conductivity 6.3 × 10⁻⁶). 7 S / m).

[0081] Port definition: The input and output ports are set as waveguide ports, and the excitation mode is TE10.

[0082] Results: The model is as follows Figure 1 As shown, the electric field distribution simulation reveals the initial polarization state. Figure 1 This is the front view of the COMSOL model in this example, used for initial verification.

[0083] Step 2: Adjust parameters and scan length Rotation angle setting: In COMSOL, use "Parametric Scan" to set the metal wire rotation angle to 90° (i.e., π / 2 radians).

[0084] Length scan: Set the length variable L from 0.5 cm to 2.0 cm and run frequency domain analysis. Extract the S11 and S21 data.

[0085] Results Analysis: Using Origin to plot the results... Figure 3 The curves shown are as follows. When L = 1.2 cm, S11 = -30 dB and S21 = -0.5 dB, with the largest difference. Therefore, the optimal length is determined to be 1.2 cm.

[0086] 3D model export: Import parameters into SOLIDWORKS to build. Figures 4 to 6 The model shown. Figure 3 The length scan results in this example guide the selection of the optimal length. Figures 4 to 6 This is the SOLIDWORKS model for this example, showing a 90° rotated structure.

[0087] Step 3: 3D Printing and Manufacturing A photopolymer 3D printer was used, and the material was photosensitive resin.

[0088] After printing, a 500 nm silver layer is deposited on the resin surface by electroplating to form a metal line.

[0089] physical objects Figure 8 As shown, the dimensions are precise and the torsion structure is clear. Figure 7 This is a 3D printed object used for subsequent testing.

[0090] Step 4: Testing and Evaluation Test system: The terahertz source (1.5 THz) is coupled to the input end via optical fiber, and the output end is connected to the detector.

[0091] Polarization measurement: Rotate the polarizer to measure P. max =1.2mW, P min =0.012mW.

[0092] PER calculation: PER=10 =20dB (initial value).

[0093] Assessment: Below the 40 dB threshold, optimization is required.

[0094] Step 5: Iterative optimization First iteration: Adjust the metal line spacing from 100 μm to 150 μm, retest, and PER improved to 35dB.

[0095] Second iteration: Low-loss resin was used, and PER was increased to 42 dB, meeting the requirements.

[0096] Data recording: Record rotation angle, transmission efficiency, etc. The final optimal parameters are a rotation angle of 90°, a length of 1.2cm, and a spacing of 150μm.

[0097] Performance Summary The final PER is 42 dB, the insertion loss is 0.8 dB, and the operating frequency band is 1 THz to 3 THz. Figure 9 The relationship between polarization extinction ratio and frequency was shown, verifying the broadband performance. Figure 9The graph shows the relationship between polarization extinction ratio and frequency in this example, illustrating the broadband performance.

[0098] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for designing a dual-waveguide polarization rotator model, characterized in that, Includes the following steps: Acquire the polarization rotation parameters of the terahertz guided wave, including the target rotation angle, operating frequency band, and insertion loss requirements; Based on the polarization rotation parameters, a geometric shape is constructed using simulation software to form a double-wire waveguide structure. The double-wire waveguide structure includes two parallel and non-coplanar metal wires and a multilayer dielectric layer that is sequentially wrapped around the outside of the metal wires from the inside out. The two ends of the metal wires are respectively set as optical signal input ports and optical signal output ports. Based on the polarization rotation parameters and the dual-wire waveguide structure, the rotation angle and optimal length of the two metal wires in the adjacent dielectric layer are adjusted to build a three-dimensional simulation model of the polarization rotator. The constructed 3D simulation model was 3D printed to obtain the physical model of the dual-line waveguide polarization rotator. A light source is coupled from the dual-waveguide polarization rotator model entity to two metal wires via optical fiber and connected to the optical signal input end of the metal wires. A photodetector is connected to the optical signal output end of the metal wires to obtain the polarization state and polarization extinction ratio of the dual-waveguide polarization rotator model entity under different optical signals. Based on the polarization extinction ratio, evaluate the quality performance of the dual-wire waveguide polarization rotator model entity under the current polarization state. Based on the quality performance evaluation results, repeat the above steps, record the rotation angles of the two metal lines corresponding to different polarization states, and obtain the optical signal transmission efficiency and loss index under different polarization states through a photodetector. Compare with the preset values ​​to obtain the rotation angles of the two metal lines under the optimal polarization state, and complete the final design of the dual-wire waveguide polarization rotator model.

2. The method for designing a dual-waveguide polarization rotator model according to claim 1, characterized in that, The polarization extinction ratio is determined according to the following formula: PER=10 ), Where PER is the polarization extinction ratio. For the maximum polarized light intensity, This represents the minimum polarized light intensity.

3. The method for designing a dual-waveguide polarization rotator model according to claim 2, characterized in that, The quality performance of the dual-waveguide polarization rotator model in the current polarization state is determined by the following formula: PER≥A Where PER is the polarization extinction ratio and A is the optimal extinction ratio.

4. The method for designing a dual-waveguide polarization rotator model according to claim 1, characterized in that, The dielectric layer includes at least a first dielectric layer, a second dielectric layer, a third dielectric layer, and a fourth dielectric layer. The first dielectric layer, the third dielectric layer, and the fourth dielectric layer are all air, and there is a gap between the third dielectric layer and the fourth dielectric layer. The second dielectric layer is made of resin.

5. The method for designing a dual-waveguide polarization rotator model according to claim 4, characterized in that, The first dielectric layer, the second dielectric layer, the third dielectric layer, and the fourth dielectric layer are arranged in a layered structure with an annular cross-section, arranged sequentially from the inside out, and the axes of the first dielectric layer, the second dielectric layer, the third dielectric layer, and the fourth dielectric layer coincide.

6. The method for designing a dual-waveguide polarization rotator model according to claim 1, characterized in that, The shape of the metal wire includes, but is not limited to, a cylindrical shape, and the bilinear waveguide structure formed by two metal wires includes, but is not limited to, a bicolumnar structure.

7. The method for designing a dual-waveguide polarization rotator model according to claim 1, characterized in that, The two metal wires have a double helix structure, and the helix twist angle of the metal wires is [0, 2π].

8. The method for designing a dual-waveguide polarization rotator model according to claim 1, characterized in that, The method for determining the optimal length of the two metal wires is as follows: The rotation angles of the two metal wires are determined, and the length of the metal wires is scanned using simulation software to obtain the scattering parameters of the metal wires at different lengths. The scattering parameters include return loss and insertion loss. Based on the length transformation of the metal wires, the maximum difference between the return loss and insertion loss is obtained. The metal wire length corresponding to the maximum difference is the required optimal metal wire length.

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