A method of applying a coated film to regulate an electric field in an infrared waveguide

Abstract

This invention relates to the field of infrared optoelectronics, specifically to a method for applying coating-based electric field modulation technology to infrared waveguides. The method includes: providing a pair of opposing waveguide electrodes to form a waveguide structure; depositing a multilayer gradient dielectric constant insulating coating on a localized region of the waveguide electrodes' surface; setting a subwavelength dual-grating structure at the edge of the multilayer gradient dielectric constant insulating coating; integrating a programmable metasurface dynamic electric field modulation layer above the multilayer gradient dielectric constant insulating coating for dynamically adjusting the local electric field distribution; and setting a closed-loop adaptive impedance matching network on both sides of the waveguide electrodes and the coating. This invention alters the conductivity and effective dielectric environment of the waveguide electrode surface through the multilayer gradient dielectric constant insulating coating, weakening the local electric field intensity and forming a weakened electric field region along the propagation direction. This suppresses higher-order modes and preferentially propagates lower-order modes, achieving efficient and programmable mode selection and electric field modulation in infrared waveguides.

Description

Technical Field

[0001] This invention relates to the field of infrared optoelectronics technology, specifically a method for applying coating-controlled electric field technology to infrared waveguides. Background Technology

[0002] Infrared waveguide devices have wide applications in laser transmission, optical communication, infrared sensing, and spectral analysis. In waveguide lasers and optical waveguide transmission systems, mode purity directly affects beam quality, transmission loss, and device performance. The presence of higher-order modes leads to an increase in beam divergence angle, a deterioration in the beam quality factor M², a decrease in coupling efficiency, and an increase in transmission loss.

[0003] Traditional methods for suppressing higher-order modes include designing bent waveguides, using mode couplers, Bragg gratings, or leaky waveguide structures. However, these methods generally suffer from problems such as high additional losses (1–3 dB), narrow operating bandwidth (±50 nm), limited dynamic tunability, and complex fabrication. Especially in the infrared band, due to the longer wavelength, traditional mode selection structures are large in size, making it difficult to achieve compact and efficient integration. Summary of the Invention

[0004] The purpose of this invention is to provide a method for applying coating-controlled electric field technology to infrared waveguides, in order to solve the problems mentioned in the background art, such as the difficulty in efficiently suppressing high-order modes in infrared waveguides, the large additional losses of mode selection devices, and the lack of dynamic adjustment capabilities.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for applying coating-controlled electric field technology in infrared waveguides, comprising the following steps:

[0006] (1) Provide a pair of waveguide electrodes arranged opposite each other to form a waveguide structure;

[0007] (2) Deposit a multilayer gradient dielectric insulating coating in a localized area on the surface of the waveguide electrode;

[0008] (3) The edge of the multilayer gradient dielectric constant insulating coating is provided with a subwavelength dual grating structure to suppress edge scattering;

[0009] (4) A programmable metasurface dynamic electric field control layer is integrated above the multilayer gradient dielectric constant insulating coating to dynamically adjust the local electric field distribution;

[0010] (5) A closed-loop adaptive impedance matching network is provided on both sides of the waveguide electrode and the coating;

[0011] By altering the conductivity and effective dielectric environment of the waveguide electrode surface through the multilayer gradient dielectric constant insulating coating, the local electric field intensity is weakened, forming an electric field weakening region along the propagation direction. This suppresses higher-order modes and promotes the propagation of lower-order modes, thereby achieving mode selection and electric field modulation.

[0012] Preferably, the coverage area of ​​the multilayer gradient dielectric constant insulating coating is dynamically determined by the difference ratio of the electric field distribution between the higher-order mode and the fundamental mode, and the coverage length is 0.3 to 0.8 times the Rayleigh length.

[0013] Preferably, the multilayer gradient dielectric constant insulating coating includes at least: a high dielectric constant bottom layer with a relative dielectric constant ≥ 20; a dielectric constant transition layer with a relative dielectric constant between 5 and 20; and a low dielectric constant surface layer with a relative dielectric constant ≤ 5.

[0014] Preferably, the period of the subwavelength dual grating structure is less than 1 / 2 of the working wavelength, the structure depth is 0.5 to 2 μm, the grating shape is rectangular, sinusoidal or trapezoidal, and the two sets of gratings are perpendicular to each other or at an angle of 30° to 60°.

[0015] Preferably, the programmable metasurface dynamic electric field control layer is composed of a subwavelength metal or dielectric resonant unit array, each resonant unit integrating a PIN diode or varactor diode, and the bias voltage is independently controlled by an external FPGA or microcontroller to achieve dynamic adjustment of the local dielectric constant.

[0016] Preferably, the closed-loop adaptive impedance matching network includes: a series inductor array, an adjustable capacitor array, a directional coupler or a standing wave ratio (SWR) detection module, and a microcontroller; the microcontroller monitors the input SWR in real time and adjusts the connection values ​​of the inductor array and capacitor array through a feedback algorithm to make the input SWR ≤ 1.2.

[0017] Preferably, the method further includes: a conductive buffer layer, made of Ti, Cr or NiCr alloy, with a thickness of 5 to 20 nm, between the waveguide electrode and the multilayer gradient dielectric constant insulating coating, to improve the adhesion and thermal stability of the coating.

[0018] Preferably, the effective dielectric constant gradient of the electric field weakening region decreases monotonically or linearly along the propagation direction, which is used to gradually reduce the lateral binding ability of higher-order modes.

[0019] Preferably, the method is applied to the mid-infrared or far-infrared band, with an operating wavelength range of 3–30 μm, and the waveguide type is a parallel plate waveguide, a channel waveguide, or a loaded strip waveguide.

[0020] Preferably, the total thickness of the multilayer gradient dielectric constant insulating coating is 0.2 to 1.5 μm, and the thickness of each sublayer is gradually distributed along the propagation direction. The high dielectric constant bottom layer near the waveguide electrode has the largest thickness, and the low dielectric constant surface layer far from the electrode has the smallest thickness, so as to form a dual gradient of dielectric constant along the thickness direction and the propagation direction.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The method of applying the coating-modulated electric field technology to infrared waveguides is to set up a multilayer gradient dielectric constant insulating coating to form a dielectric constant gradient along the propagation direction on the surface of the waveguide electrode, thereby locally weakening the electric field strength, reducing the fundamental mode transmission loss by more than 80%, and improving the high-order mode suppression ratio to more than 15dB.

[0023] 2. The method of applying this coating-controlled electric field technology to infrared waveguides effectively suppresses scattering loss caused by abrupt changes in dielectric constant by setting a subwavelength dual grating structure at the edge of the coating, thus extending the working bandwidth to ±220nm.

[0024] 3. The method of applying this coating-controlled electric field technology to infrared waveguides integrates a programmable metasurface dynamic electric field control layer, and independently controls each resonant unit through external voltage to achieve real-time dynamic adjustment of the local electric field distribution, and has programmability.

[0025] 4. The method of applying this coating-controlled electric field technology to infrared waveguides is to set up a closed-loop adaptive impedance matching network, monitor and adjust the impedance matching state in real time, ensure that the input VSWR is ≤1.2, and guarantee the efficient coupling of RF power. Attached Figure Description

[0026] Figure 1 This is an overall flowchart of the present invention;

[0027] Figure 2 This is a flowchart illustrating the structure and function of the gradient dielectric constant coating of the present invention.

[0028] Figure 3 This is a functional flowchart of the subwavelength dual grating of the present invention;

[0029] Figure 4 This is a flowchart of the programmable metasurface control process of the present invention;

[0030] Figure 5 This is a flowchart of the closed-loop adaptive impedance matching network of the present invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] The structure of the method for applying coating-modulated electric field technology to infrared waveguides provided by this invention is as follows: Figure 1 As shown, it includes the following steps:

[0033] Step 1: Provide waveguide electrodes

[0034] A pair of opposing waveguide electrodes are provided to form a waveguide structure. The electrode material can be gold, copper, or other highly conductive metals. The electrode spacing is determined based on the operating wavelength and waveguide type; for parallel plate waveguides, the electrode spacing is typically 10–30 μm. In this step, the waveguide electrode layer can be deposited on a substrate (such as Si or Ge) by electron beam evaporation or magnetron sputtering.

[0035] Step 2: Deposit a multilayer gradient dielectric insulating coating

[0036] like Figure 2 A multilayer dielectric insulating coating with gradient dielectric constants is deposited in a localized region on the surface of the waveguide electrode. The coverage area is dynamically determined by the difference in electric field distribution between the higher-order mode and the fundamental mode, and the coverage length is 0.3 to 0.8 times the Rayleigh length. The coating includes at least: a high-dielectric-constant underlayer (relative permittivity ≥ 20), a dielectric-constant transition layer (relative permittivity between 5 and 20), and a low-dielectric-constant toplayer (relative permittivity ≤ 5). Each layer can be deposited sequentially by magnetron sputtering combined with atomic layer deposition (ALD). The effective dielectric constant gradient in the electric field weakening region decreases monotonically or piecewise linearly along the propagation direction, which is used to gradually reduce the lateral confinement ability of the higher-order modes.

[0037] Furthermore, the total thickness of the multilayer gradient dielectric insulating coating is 0.2–1.5 μm, and the thickness of each sublayer gradually varies along the propagation direction. The high dielectric constant bottom layer near the waveguide electrode has the largest thickness, while the low dielectric constant surface layer away from the electrode has the smallest thickness, thus forming a dual gradient of dielectric constant along both the thickness and propagation directions.

[0038] Specifically, by setting a structure where the bottom layer is thickest near the electrode and the surface layer is thinnest away from the electrode, combined with the gradient changes in the dielectric constant of each layer, a dual dielectric constant gradient is formed along both the thickness direction and the propagation direction. This dual gradient structure can more effectively guide the electric field to smoothly transition from the electrode surface to the waveguide center, further weakening the electric field intensity of higher-order modes near the electrode, while reducing reflection and scattering losses caused by abrupt changes in dielectric constant, thereby improving the fundamental mode selectivity and transmission efficiency.

[0039] Step 3: Fabrication of subwavelength dual-grating structure

[0040] like Figure 3 A subwavelength dual-grating structure is set at the edge of a multilayer gradient dielectric constant insulating coating to suppress edge scattering caused by abrupt changes in dielectric constant. The period of the dual grating is less than half of the working wavelength, the structure depth is 0.5–2 μm, and the grating shape is rectangular, sinusoidal, or trapezoidal. The two sets of gratings are perpendicular to each other or at an angle of 30°–60°. They can be fabricated by electron beam lithography combined with inductively coupled plasma (ICP) etching.

[0041] Step 4: Integrating a programmable metasurface dynamic electric field control layer

[0042] like Figure 4 A programmable metasurface dynamic electric field modulation layer is integrated above a multilayer gradient dielectric constant insulating coating. This modulation layer consists of an array of subwavelength metal or dielectric resonant units, each integrating a PIN diode or varactor diode. The bias voltage (e.g., 0–5V) is independently controlled by an external FPGA or microcontroller to achieve dynamic adjustment of the local dielectric constant, thereby dynamically regulating the local electric field distribution. The metasurface resonant units are defined using a stripping process, and the diodes are bonded together.

[0043] Step 5: Set up the closed-loop adaptive impedance matching network

[0044] like Figure 5 A closed-loop adaptive impedance matching network is set on both sides of the waveguide electrode and the coating, including: a series inductor array, an adjustable capacitor array, a directional coupler or a VSWR detection module, and a microcontroller. The microcontroller monitors the input VSWR in real time and adjusts the connection values ​​of the inductor array and capacitor array through a feedback algorithm (such as a PID algorithm) to ensure that the input VSWR is ≤1.2. In specific implementations, surface-mount inductors, capacitors, and control chips can be used to construct the impedance matching network.

[0045] Through the above steps, the conductivity and effective dielectric environment of the waveguide electrode surface are changed by using a multilayer gradient dielectric constant insulating coating, which weakens the local electric field intensity and forms an electric field weakening region along the propagation direction. This suppresses higher-order modes and promotes the propagation of lower-order modes, thereby achieving mode selection and electric field control.

[0046] Example 1

[0047] This embodiment provides an infrared parallel plate waveguide device for a wavelength λ=10.6μm (typical band for CO2 lasers). The device structure consists of upper and lower waveguide electrodes made of gold (Au) material with a thickness of 200nm and an electrode spacing of 12μm. A gradient dielectric constant insulating plating is deposited in a localized region on the inner surface of the electrodes, with a coverage length L_c=0.5×Rayleigh length.

[0048] Coating structure (from electrode outward): Bottom layer: HfO2, ε r =22, thickness 100nm; transition layer: Al2O3 doped with HfO2 (1:1), ε r =12, thickness 80nm; surface layer: SiO2, ε r =3.9, thickness 60nm.

[0049] Subwavelength dual grating: period 4.5μm (<λ / 2), depth 1.2μm, rectangular grating, two sets of gratings with an included angle of 45°, located at the beginning and end edges of the coating.

[0050] Metasurface layer: Gold resonant ring array with a period of 5μm. GaAs PIN diodes are integrated at the ring openings and biased by FPGA from 0 to 5V for fine-tuning the local electric field.

[0051] Impedance matching network: series inductor array (1~20nH, 0.5nH step) + BST adjustable capacitor array, VSWR detection uses directional coupler + AD8302, microcontroller STM32F103 real-time PID adjustment to make VSWR ≤1.15.

[0052] The performance comparison between the device of Embodiment 1 of the present invention and a conventional waveguide is shown in the table below:

[0053]

[0054] As shown in the table above, under an input power of 1W, the fundamental mode transmission loss is 0.42dB, the LP11 mode rejection ratio is 17.3dB, and the standing wave ratio is 1.12. Therefore, compared with the traditional parallel plate waveguide, the device of Embodiment 1 of the present invention has achieved significant and unexpected technical effects in six key performance indicators: fundamental mode transmission loss, higher-order mode rejection ratio, input standing wave ratio, peak electric field intensity, operating bandwidth, and programmable adjustment capability, which fully demonstrates the effectiveness and advancement of the technical solution of the present invention.

[0055] Example 2

[0056] This embodiment provides an application with different wavelengths and waveguide types. The operating wavelength λ = 4.5 μm (mid-infrared band) utilizes a channel waveguide structure, with copper as the electrode material and an electrode spacing of 8 μm. The coating coverage length L... C =0.7 × Rayleigh length.

[0057] Coating structure (from electrode outwards): Bottom layer: TiO2, ε r =45, thickness 70nm; transition layer: TiO2-Si3N4 composite (volume ratio 1:1), ε r =15, thickness 60nm; surface layer: MgF2, ε r =1.9, thickness 50nm.

[0058] Subwavelength dual grating: period 1.8μm (<λ / 2), depth 0.6μm, sinusoidal grating, with the two sets of gratings at an angle of 60°.

[0059] Metasurface layer: Dielectric resonant unit array, integrated varactor diode, with a 0-3V bias voltage provided by a microcontroller.

[0060] Impedance matching network: series inductor array (0.5~10nH) + BST adjustable capacitor array, VSWR control ≤1.2.

[0061] Results: Under an input power of 0.5 W, the fundamental mode transmission loss is 0.38 dB / cm, the higher-order mode rejection ratio is 18.1 dB, and the input VSWR is 1.15. Compared with traditional channel waveguides (without coating), the fundamental mode loss is reduced by 82%, and the higher-order mode rejection ratio is improved by 90 times.

[0062] In the manufacturing process of this invention: First, waveguide electrodes (Au / Cu / Ti) are deposited on a Si or Ge substrate by electron beam evaporation; high-K, medium-K, and low-K coatings are deposited sequentially by magnetron sputtering and ALD; second, subwavelength dual gratings are fabricated by electron beam lithography and ICP etching; third, metasurface resonant units are defined by a lift-off process and diodes are bonded; next, inductors, capacitors, and control chips are surface-mounted to complete the impedance matching network; finally, the device is packaged and connected to an external control interface.

[0063] In use, this invention first applies an excitation signal to the waveguide electrodes via an external RF power supply. The directional coupler in the closed-loop adaptive impedance matching network continuously monitors the VSWR at the input. The microcontroller dynamically adjusts the connection parameters of the series inductor array and the adjustable capacitor array based on the detected value, ensuring a VSWR ≤ 1.2 and achieving efficient coupling of RF power.

[0064] After RF power coupling, a discharge electric field is formed between the waveguide electrodes. Due to the deposition of multiple layers of gradient dielectric insulating plating on the local surface of the waveguide electrodes, the conductivity of the electrode surface in this region is weakened, and the effective dielectric environment is changed, resulting in a significant decrease in the local electric field strength, forming a weakened electric field region along the propagation direction. In this region, the electric field distribution of higher-order modes is closer to the electrode surface and is more affected by the plating, resulting in a significant reduction in their gain; while the electric field energy of the fundamental mode is concentrated in the central region of the waveguide, less affected by the plating, and thus propagates preferentially.

[0065] Meanwhile, the subwavelength dual-grating structure set at the edge of the coating suppresses scattering loss caused by abrupt changes in dielectric constant through its subwavelength periodic structure, ensuring a smooth transition of the electric field. Under the control of an external FPGA or microcontroller, the programmable metasurface dynamic electric field control layer independently changes the local dielectric constant by adjusting the bias voltage of the PIN diodes or varactor diodes in each resonant unit, thereby achieving real-time dynamic fine-tuning of the electric field distribution.

[0066] Through the aforementioned electric field modulation, higher-order modes are effectively suppressed, while lower-order (fundamental) modes propagate and are output preferentially, thus achieving mode selection and electric field modulation in the infrared waveguide. When the operating wavelength or output mode requirements change, the bias voltage configuration of the metasurface modulation layer can be reprogrammed to dynamically adapt to the new operating conditions.

[0067] Based on the above, a table comparing the present invention with the prior art is as follows:

[0068]

[0069] As can be seen from the table above, this invention, while maintaining moderate process complexity, significantly outperforms all existing technologies in three dimensions: additional loss, dynamic adjustability, and VSWR control, achieving unexpected technical effects.

[0070] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for applying coating-controlled electric field technology to infrared waveguides, characterized in that, Includes the following steps: (1): Provide a pair of waveguide electrodes arranged opposite each other to form a waveguide structure; (2): Deposit a multilayer gradient dielectric insulating coating in a localized area on the surface of the waveguide electrode; (3): The edges of the multilayer gradient dielectric constant insulating coating are provided with a subwavelength dual grating structure to suppress edge scattering; (4): A programmable metasurface dynamic electric field control layer is integrated above the multilayer gradient dielectric constant insulating coating to dynamically adjust the local electric field distribution; (5): A closed-loop adaptive impedance matching network is provided on both sides of the waveguide electrode and the coating; By altering the conductivity and effective dielectric environment of the waveguide electrode surface through the multilayer gradient dielectric constant insulating coating, the local electric field intensity is weakened, forming an electric field weakening region along the propagation direction. This suppresses higher-order modes and promotes the propagation of lower-order modes, thereby achieving mode selection and electric field modulation.

2. The method for applying the coating-controlled electric field technology to infrared waveguides according to claim 1, characterized in that: The coverage area of ​​the multilayer gradient dielectric constant insulating coating is dynamically determined by the difference ratio of the electric field distribution between the higher-order mode and the fundamental mode, and the coverage length is 0.3 to 0.8 times the Rayleigh length.

3. The method for applying the coating-controlled electric field technology to infrared waveguides according to claim 1, characterized in that: The multilayer gradient dielectric constant insulating coating includes at least: High dielectric constant bottom layer, relative dielectric constant ≥20; A dielectric constant transition layer with a relative permittivity between 5 and 20; Low dielectric constant surface layer, relative dielectric constant ≤ 5.

4. The method for applying the coating-controlled electric field technology according to claim 1 to infrared waveguides, characterized in that: The period of the subwavelength dual grating structure is less than 1 / 2 of the working wavelength, the structure depth is 0.5 to 2 μm, the grating shape is rectangular, sinusoidal or trapezoidal, and the two sets of gratings are perpendicular to each other or at an angle of 30° to 60°.

5. The method for applying the coating-controlled electric field technology according to claim 1 to infrared waveguides, characterized in that: The programmable metasurface dynamic electric field control layer is composed of a subwavelength metal or dielectric resonant unit array, and each resonant unit integrates a PIN diode or varactor diode.

6. The method for applying the coating-controlled electric field technology according to claim 1 to infrared waveguides, characterized in that: The closed-loop adaptive impedance matching network includes: a series inductor array, an adjustable capacitor array, a directional coupler or a standing wave ratio (SWR) detection module, and a microcontroller; the microcontroller monitors the input SWR in real time and adjusts the connection values ​​of the inductor array and capacitor array through a feedback algorithm to make the input SWR ≤ 1.

2.

7. The method for applying the coating-controlled electric field technology according to claim 1 to infrared waveguides, characterized in that: Also includes: A conductive buffer layer is provided between the waveguide electrode and the multilayer gradient dielectric constant insulating coating. The material is Ti, Cr or NiCr alloy, and the thickness is 5 to 20 nm. This layer is used to improve the adhesion and thermal stability of the coating.

8. The method for applying the coating-controlled electric field technology according to claim 1 to infrared waveguides, characterized in that: The effective dielectric constant gradient in the electric field weakening region decreases monotonically or piecewise linearly along the propagation direction, which is used to gradually reduce the lateral binding ability of higher-order modes.

9. The method for applying the coating-controlled electric field technology according to claim 3 to infrared waveguides, characterized in that: The total thickness of the multilayer gradient dielectric constant insulating coating is 0.2 to 1.5 μm, and the thickness of each sublayer is gradually distributed along the propagation direction. The high dielectric constant bottom layer near the waveguide electrode has the largest thickness, while the low dielectric constant surface layer far from the electrode has the smallest thickness, so as to form a dual gradient of dielectric constant along the thickness direction and the propagation direction.

10. The method for applying the coating-controlled electric field technology according to claim 1 to infrared waveguides, characterized in that: The method is applied to the mid-infrared or far-infrared bands, with a working wavelength range of 3–30 μm, and the waveguide type is a parallel plate waveguide, a channel waveguide, or a loaded strip waveguide.

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