A waveguide electrode coating process processing method

Abstract

This invention relates to the field of laser manufacturing technology, specifically to a waveguide electrode coating process. The method involves calculating the total offset between the actual and theoretical beam waist positions using two-dimensional optical field scanning and Gaussian fitting to determine if the positioning is qualified, and then defining the coating processing area to ensure accurate coating positioning. A titanium bonding layer, a gradient transition layer, and a ceramic layer are sequentially deposited on the pre-treated electrode surface. The gradient transition layer is divided into equal-thickness sublayers, and the nitrogen flow rate is calculated. The number of sublayers is determined by thermal stress back-calculation, significantly reducing interfacial thermal stress and preventing coating cracking and peeling. The ceramic layer deposition is divided into three stages: interfacial nucleation, columnar crystal growth, and surface smoothing. Residual stress is monitored using an in-situ quartz crystal microbalance, and the pulse bias is adjusted in a closed-loop manner to achieve process control. An edge-gradient transition region is prepared, and the coating performance is verified. An impedance matching compensation network is constructed to monitor the standing wave ratio and discharge voltage fluctuations in real time for dynamic adjustment, ensuring effective RF power coupling and stable discharge.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of laser manufacturing, in particular to a waveguide electrode coating process machining method. BACKGROUND

[0002] In a waveguide gas laser, in order to suppress high-order modes and preferentially output the lowest-order waveguide mode to improve beam quality, the prior art often adopts the mode of setting a physical recess (groove) at the position corresponding to the beam waist on the inner surface of the electrode plate, the continuous constraint of the waveguide tube is broken by removing part of the electrode material, so that the electric field intensity of the region is weakened, and a free space propagation region favorable to the fundamental mode is formed; this scheme is feasible in principle, but the recess structure has problems of low machining precision, poor consistency and high cost.

[0003] Specifically, the recess structure needs to precisely mechanically groove the hard electrode material, which is difficult to process and difficult to ensure the consistency of the recess size (length, depth); the recess destroys the structural integrity of the electrode plate, reduces the mechanical strength and heat dissipation performance; if the recess edge is a steep step, an electric field concentration point is easily formed, which may cause gas breakdown under high-power radio frequency discharge conditions, leading to device failure; in addition, the geometric parameters of the recess are limited by the mechanical processing capacity, and it is difficult to flexibly adjust to adapt to different resonant cavity design requirements.

[0004] Therefore, there is an urgent need for a new waveguide mode structure scheme that can realize equivalent electric field regulation and avoid the defects of the recess structure; the application proposes to set an insulating coating layer on the inner surface of the electrode plate at the region corresponding to the beam waist, to locally weaken the electric field constraint in the region by using the difference in conductivity between the insulating material and the conductive electrode, and to form a free space propagation region to preferentially select the lowest-order waveguide mode. SUMMARY

[0005] In view of the above-mentioned shortcomings of the prior art, the application provides a waveguide electrode coating process machining method, which can effectively solve the problems of recess machining difficulty, weak structure and edge easy breakdown in the background art.

[0006] To solve the above technical problems, the application adopts the following technical scheme: the application provides a waveguide electrode coating process machining method, comprising:

[0007] S1, a two-dimensional coordinate system corresponding to the waveguide electrode to be machined is constructed, the actual position of the beam waist on the inner surface of the waveguide electrode to be machined is calculated, and the total offset amount of the actual position of the beam waist and the theoretical position is calculated.

[0008] According to the total offset amount, it is judged whether the positioning is qualified, and if qualified, the insulating coating layer machining area is demarcated with the actual position of the beam waist as the core.

[0009] S2. Based on the area processed by the insulating coating, the inner surface of the waveguide electrode to be processed is pretreated.

[0010] An insulating coating is formed by depositing a titanium bonding layer, a gradient transition layer, and a ceramic layer on the inner surface of the pretreated electrode.

[0011] The gradient transition layer is divided into equal-thickness sublayers, and the nitrogen flow rate corresponding to the deposition of each equal-thickness sublayer is calculated.

[0012] S3. Based on the completed deposition of the titanium bonding layer and gradient transition layer, the ceramic layer deposition process is divided into three independent stages, including the interface nucleation stage, the columnar crystal growth stage, and the surface planarization stage. Combined with the pre-set allowable residual stress fluctuation range for each stage, the ceramic layer deposition process is evaluated.

[0013] S4. Prepare the edge gradient transition region of the corresponding electrode and verify whether the coating performance meets the design requirements.

[0014] S5. Measure the equivalent capacitance introduced by the insulating coating, calculate and adjust the compensation inductance value, construct the impedance matching compensation network, and monitor the standing wave ratio and discharge voltage fluctuations in real time for dynamic debugging until the impedance matching compensation network is qualified.

[0015] Preferably, the specific process for calculating the total offset between the actual and theoretical positions of the beam waist includes:

[0016] A unique two-dimensional reference coordinate system is constructed with the lower left corner of the inner surface of the waveguide electrode to be processed as the origin, the electrode length extension direction as the X-axis, and the electrode width extension direction as the Y-axis.

[0017] A full-domain grid scan is performed on the waveguide discharge region on the inner surface of the electrode along the X and Y axes, and the coordinates and corresponding light field intensity of each scan point are collected in real time.

[0018] By combining the coordinates and light field intensity of each scanning point, fitting calculations are used to solve for the beam waist center coordinates, beam waist spot radius in the horizontal axis direction, and beam waist spot radius in the vertical axis direction corresponding to the waveguide electrode to be processed.

[0019] By obtaining the theoretical beam waist center coordinates and combining them with the beam waist center coordinates corresponding to the waveguide electrode to be processed, the total offset between the actual beam waist center and the theoretical beam waist center is calculated.

[0020] Preferably, the specific process of determining whether the positioning is qualified based on the total offset includes:

[0021] Obtain the coverage width of the insulating coating in the direction of the corresponding electrode width of the waveguide electrode to be processed, as well as the width of one side of the gradient transition zone at the edge of the coating, and calculate the equivalent coverage width of the electric field region corresponding to the waveguide electrode to be processed.

[0022] By combining the beam waist spot radius in the horizontal axis direction and the beam waist spot radius in the vertical axis direction, the equivalent spot radius at the center of the beam waist is calculated.

[0023] By combining the equivalent coverage width of the electric field region corresponding to the waveguide electrode to be processed and the equivalent spot radius at the beam waist center, the maximum allowable offset threshold between the actual beam waist center and the theoretical beam waist center is calculated.

[0024] The positioning is judged to be qualified by combining the total offset between the actual beam waist center and the theoretical beam waist center with the maximum allowable offset threshold.

[0025] Preferably, the specific process for analyzing the nitrogen flow rate during the deposition of each equal-thickness sublayer includes:

[0026] The total thickness of the gradient transition layer is divided into equal-thickness sub-layers along the thickness direction, and the titanium volume fraction corresponding to each sub-layer is calculated.

[0027] Obtain the equivalent thermal expansion coefficients of the gradient transition layer, aluminum nitride, and titanium. Obtain the equivalent shear modulus of the gradient transition layer, the shear modulus of aluminum nitride, and titanium, as well as the bulk modulus of aluminum nitride and titanium. Combine this with the titanium volume fraction of each sublayer to calculate the equivalent thermal expansion coefficient of each sublayer.

[0028] Based on the equivalent thermal expansion coefficient, the abrupt change in thermal expansion coefficient between adjacent sublayers is calculated.

[0029] The equivalent Poisson's ratio of each sublayer is calculated by combining the equivalent shear modulus and the equivalent bulk modulus.

[0030] By combining the abrupt change in the coefficient of thermal expansion between adjacent sublayers and the temperature rise during electrode operation, the thermal stress at the corresponding interface of each sublayer is calculated.

[0031] Based on the preset allowable upper limit of interfacial thermal stress, the number of equal-thickness sub-layers is analyzed along the thickness direction of the total thickness of the gradient transition layer.

[0032] To obtain the sputtering yield of the target material, based on the titanium volume fraction of each sublayer, combined with the atomic mass of titanium, the atomic mass of aluminum, the single atom volume of titanium, and the single molecule volume of aluminum nitride, the sputtering power of the titanium target and the sputtering power of the aluminum target for each sublayer are calculated. The basic nitrogen flow rate and the maximum nitrogen flow rate are obtained, and then the nitrogen flow rate during the deposition of each sublayer is calculated.

[0033] Preferably, the deposition process of the ceramic layer is as follows:

[0034] The ceramic layer deposition was performed in three stages, with each stage using a reference bias voltage that matched the corresponding deposition requirements.

[0035] During the deposition process, the residual stress of the film layer is acquired in real time through an in-situ stress monitoring device. Based on the monitoring data, the pulse bias voltage is adjusted in a closed loop to control the residual stress within a preset range.

[0036] After deposition, the vacuum and clamping conditions are kept unchanged, and the coating is tested in situ. After passing the test, the edge gradient transition zone of the coating is prepared in a vacuum environment.

[0037] Preferably, the specific process for preparing the edge gradient transition region is as follows:

[0038] Obtain the width of the single-sided edge gradient transition region and the rated thickness of the flat region of the ceramic layer corresponding to the waveguide electrode to be processed. Define the distance L from any position of the gradient region to the edge of the flat region and determine the target thickness at that position.

[0039] Among them, when When the target thickness is 0, it equals the rated thickness of the flat region of the ceramic layer. When the target thickness is equal to the width of the gradient transition zone on one side edge, the target thickness is equal to 0.

[0040] By combining the measured deposition rate of the ceramic layer with the effective deposition time corresponding to the position at a horizontal distance L from the edge of the flat area, the target thickness equation and the actual deposition thickness equation are solved simultaneously to obtain a constant mask moving speed.

[0041] Drive the mask at a constant speed from the edge of the flat region to the outside of the gradient region to complete the preparation of the single-sided edge gradient transition region.

[0042] Preferably, the process of verifying whether the coating performance meets the design requirements is as follows:

[0043] Offline comprehensive testing was conducted on the insulating coating after vacuum annealing. The test items included coating thickness uniformity, insulation performance, residual stress, and edge gradient linearity.

[0044] Once all test items meet the design requirements, the coating is deemed qualified and the process moves to waveguide electrode assembly and resonant cavity precision debugging. If any item fails to meet the standard, the insulation coating preparation is repeated.

[0045] Preferably, the specific process of constructing the impedance matching compensation network is as follows:

[0046] At the rated operating frequency of the laser RF excitation source, impedance tests were performed on the waveguide electrodes that had completed the preparation of the transition layer, flat insulating region and edge gradient region. The equivalent parallel capacitance between the electrodes introduced by the coating layer was extracted, and the standard characteristic impedance of the output transmission line of the laser excitation module was obtained.

[0047] Calculate the operating angular frequency of the radio frequency excitation based on the rated excitation frequency.

[0048] By combining the operating angular frequency and the equivalent parallel capacitance between the electrodes, the series compensation inductance required to match the capacitive load of the matching electrodes is derived.

[0049] Based on the calculated series compensation inductance, an adjustable inductor is selected and paired with an auxiliary matching capacitor to complete the initial assembly of the impedance matching compensation network.

[0050] Preferably, dynamic adjustment is performed by real-time monitoring of the standing wave ratio and discharge voltage fluctuations, and the specific process is as follows:

[0051] Connect the assembled waveguide electrode system to the laser's RF excitation transmission circuit and resonant cavity, using the rated output of the RF excitation source as the debugging benchmark.

[0052] Obtain the maximum allowable VSWR of the waveguide electrode system, the rated discharge voltage of the electrode, and the maximum allowable fluctuation amplitude of the discharge voltage.

[0053] Turn on the radio frequency excitation source and apply the rated power. Real-time acquisition of the waveguide electrode system standing wave ratio and the real-time discharge voltage of the electrode gap is performed. The absolute value of the difference between the real-time discharge voltage and the rated discharge voltage is taken to obtain the real-time fluctuation amplitude of the discharge voltage.

[0054] The current system VSWR is compared with the maximum allowable VSWR, and the current real-time fluctuation amplitude of the discharge voltage is compared with the maximum allowable fluctuation value of the discharge voltage. If both meet the threshold requirements, the debugging is qualified. Otherwise, the adjustable compensation inductor and auxiliary matching capacitor are iteratively adjusted in small steps, and the comparison is repeated until the debugging is qualified.

[0055] The technical solution provided by this invention has the following advantages compared with the known prior art:

[0056] 1. By designing a composite insulating coating structure that includes a titanium bonding layer, a gradient transition layer, a flat insulating region, and an edge gradient region, the industry pain points of poor interfacial adhesion and concentrated edge electric field in traditional single insulating coatings are fundamentally solved. The gradient transition layer achieves a smooth transition of the thermal expansion coefficient between the metal electrode and the ceramic insulating layer through compositional gradient, which greatly reduces interfacial thermal stress and effectively avoids coating cracking and peeling. The edge gradient region eliminates the electric field abrupt change at the coating edge through linear thickness gradient, which significantly suppresses the tip discharge phenomenon and improves the working stability and withstand voltage of the laser.

[0057] 2. An aluminum nitride ceramic layer deposition process employing a staged differentiated reference bias combined with in-situ quartz crystal microbalance (QCM) stress closed-loop control achieves precise control over the coating's microstructure and residual stress. Through a three-stage process—low bias to promote uniform nucleation during the interface nucleation stage, high bias to refine grains during the columnar crystal growth stage, and medium bias to reduce roughness during the surface smoothing stage—the resulting ceramic layer exhibits high density and fine, uniform grains. Furthermore, the introduction of a QCM real-time stress monitoring and pulse bias dynamic adjustment mechanism controls the residual stress of the coating within the design limits, further enhancing the coating's mechanical strength and insulation reliability.

[0058] 3. During the fabrication of the edge gradient transition region, by calculating a constant mask moving speed and driving the mask to move at a uniform speed, the coating thickness is linearly reduced from the rated value in the flat area to zero at the edge. This avoids the problems of low precision and poor consistency in traditional manual polishing or photolithography processes, effectively suppresses the concentration of the electric field at the edge, prevents gas breakdown, and improves the stability of device operation.

[0059] 4. During the impedance matching debugging process, by measuring the equivalent capacitance introduced by the coating, calculating the series compensation inductance and constructing a matching network, combined with a dynamic debugging mechanism that monitors the standing wave ratio and discharge voltage fluctuations in real time, the problems of low RF power coupling efficiency and large discharge voltage fluctuations in traditional processes are solved, ensuring effective RF power coupling and uniform and stable discharge.

[0060] 5. Standardization and controllability have been achieved from positioning and coating deposition to performance testing, including thermal stress back-calculation of the number of gradient transition layer sublayers, three-stage bias control and in-situ stress monitoring of ceramic layer deposition, and offline comprehensive testing and verification, which significantly improves process consistency and meets the needs of industrial mass production. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0062] Figure 1 This is a schematic diagram of the implementation steps of the present invention. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0064] The present invention will be further described below with reference to embodiments.

[0065] Please see Figure 1 As shown, a waveguide electrode coating process includes at least the following steps:

[0066] Step 1: Use a two-dimensional laser field to scan the waveguide electrode to be processed, perform optical path scanning and energy acquisition on the inner surface of the waveguide electrode to be processed, calculate the actual coordinates of the beam waist center corresponding to the waveguide electrode to be processed, and the total offset between the actual coordinates of the beam waist center and the theoretical beam waist center, obtain the equivalent coverage width of the electric field region corresponding to the waveguide electrode to be processed and the equivalent spot radius of the beam waist center position, calculate the maximum allowable offset threshold, and thus determine the processing area of ​​the insulating coating.

[0067] In one specific embodiment, the actual coordinates of the beam waist center corresponding to the waveguide electrode to be processed are calculated as follows: The waveguide electrode to be processed is horizontally fixed on an optical positioning fixture. The lower left corner vertex of the inner surface of the waveguide electrode to be processed is taken as the origin of the coordinate system. The direction of electrode length extension (parallel to the optical axis of the laser resonator cavity) is taken as the X-axis. The direction of extension along the electrode length toward the light-emitting side of the resonator cavity is the positive X-axis direction, and the opposite direction is the negative X-axis direction. The direction of electrode width extension (perpendicular to the optical axis and pointing to the outside of the waveguide) is taken as the Y-axis. The direction of extension along the electrode width toward the outside of the waveguide is the positive Y-axis direction, and the opposite direction is the negative Y-axis direction. Thus, a unique two-dimensional reference coordinate system is constructed.

[0068] Adjust the position of the waveguide electrode to be processed so that the X-axis of the waveguide electrode is parallel to the optical axis of the planar waveguide resonant cavity, so as to eliminate the positioning error caused by the clamping tilt.

[0069] A two-dimensional laser field scanning device was used to perform a full-area grid scan of the waveguide discharge region on the inner surface of the electrode along the X and Y axes, with a scanning step size set to 0.005 mm, and each scanning point was acquired in real time. X coordinate Y coordinate (Directly acquired by the tooling grating ruler), and the light field intensity at that location. (Measured by a light field detector). This is the index of the scan points corresponding to each acquisition time point. , The value can be a positive integer.

[0070] X coordinates of all collected scan points Y coordinate and light field intensity The fitting calculation is performed using a two-dimensional Gaussian function, and the calculation formula is as follows: ,in This is expressed as the light field intensity at a certain location. and These are represented as the X-axis coordinates and Y-axis coordinates corresponding to a certain position, respectively. The X-coordinates of all collected scan points are... Y coordinate and light field intensity Substituting the beam waist radius in the X-axis direction (optical axis direction) and the beam waist radius in the Y-axis direction (electrode width direction) into the calculation formula corresponding to the two-dimensional Gaussian function, the coordinates of the beam waist center corresponding to the waveguide electrode to be processed can be obtained. The light field intensity at the center of the beam waist and the beam waist radius along the X-axis (optical axis). The beam waist radius along the Y-axis (electrode width direction) .

[0071] Combination and Using the formula: The equivalent spot radius at the center of the beam waist was calculated. .

[0072] Obtain the coverage width of the insulating coating in the corresponding electrode width direction (Y-axis) of the waveguide electrode to be processed. And the single-sided width of the gradient transition zone at the edge of the coating. Using the formula: The equivalent coverage width of the electric field region corresponding to the waveguide electrode to be processed is calculated. .

[0073] Obtain the theoretical beam waist center coordinates given in the laser design drawings. Through the formula: The total offset between the actual beam waist center and the theoretical beam waist center was calculated. .

[0074] Combined with the equivalent coverage width of the electric field region corresponding to the waveguide electrode to be processed The equivalent spot radius at the center of the beam waist Using the formula: The maximum allowable offset threshold between the actual beam waist center and the theoretical beam waist center was calculated. .

[0075] The total offset between the actual beam waist center and the theoretical beam waist center With the maximum allowed offset threshold In comparison, if If the position is correct, it indicates that the actual beam waist center is positioned correctly; otherwise, it indicates that the actual beam waist center is positioned incorrectly. After readjusting the electrode clamping position, return to step one for repositioning until the total offset meets the judgment condition, and then proceed to step two.

[0076] It should be noted that in the Gaussian fitting function, that is The negative exponent of the natural constant indicates that the light field intensity decays from the center outwards according to a Gaussian distribution, and the light field intensity is lower the farther away from the center of the beam waist.

[0077] The theoretical beam waist center coordinates originate from the design and calculation stage of the laser resonator. Before device fabrication, designers calculate the transmission characteristics of the Gaussian beam within the resonator using structural parameters such as the cavity length, mirror curvature radius, and waveguide gap, through the ABCD transmission matrix method or resonator optical simulation software (such as LASCAD). This determines the axial position of the beam waist within the resonator (i.e., the distance from a reference end face along the optical axis). Combined with the assembly position relationship of the electrode plates within the resonator, the axial position of the beam waist is converted into coordinate values ​​in the inner surface coordinate system of the electrode. These coordinate values ​​are then marked on the laser assembly drawings as the design target values.

[0078] In the actual operation of waveguide lasers, due to factors such as non-uniform distribution of gain medium, edge effect of discharge region, and assembly error of resonant cavity, the optical field intensity distribution is not an ideal symmetrical Gaussian distribution. When using the weighted average method of optical field intensity to extract the beam waist center, the asymmetry of the optical field distribution will cause a systematic deviation between the weighted centroid and the real beam waist center. Moreover, the weighted average method can only obtain the coordinates of the beam waist center and cannot simultaneously provide the beam spot radius parameter. In the subsequent steps of this scheme, when delineating the insulating coating processing area, it is necessary to calculate the maximum allowable offset threshold based on the beam spot radius. Therefore, it is necessary to obtain both the beam waist center coordinates and the beam spot radius parameters simultaneously during the positioning stage.

[0079] The coverage width of the insulating coating is determined by the optical design of the resonant cavity. During the design phase, the required coverage width of the coating is determined based on the optical field distribution range of the reverse wave mode of the resonant cavity in the electrode width direction. The width can be taken from 1 / 2 to the entire width of the reverse wave mode. This parameter can be determined and marked in the design drawings during the optical simulation phase of the resonant cavity. The width of one side of the gradient transition zone at the edge of the coating is determined by the electric field distribution simulation. The specific method is as follows: establish a finite element simulation model of the electrode-coating-discharge region (such as using COMSOL software). Under the condition that the total coverage width of the coating remains unchanged, set different transition zone widths to perform electric field simulation, calculate the peak value of the local electric field intensity at the edge of the coating, and select the minimum transition zone width that makes the local electric field intensity at the edge not exceed the gas breakdown threshold (typical value 2.4MV / m) as the design value of the width of one side of the gradient transition zone at the edge of the coating.

[0080] In this design, an insulating coating is provided at the position of the beam waist of the resonant cavity corresponding to the waveguide electrode to be processed. The number of coating positions corresponds to the number of beam waists of the resonant cavity. For a resonant cavity with a single beam waist, a coating area is provided at the position corresponding to the beam waist. The insulating coating can be provided on either the inner surface of the upper electrode plate or the inner surface of the lower electrode plate, or the insulating coating can be provided on both the inner surfaces of the upper and lower electrode plates to form a symmetrical layout. The specific arrangement is determined according to the electric field distribution characteristics and mode selection requirements of the resonant cavity.

[0081] By designing a composite insulating coating structure that includes a titanium bonding layer, a gradient transition layer, a flat insulating region, and an edge gradient region, the industry pain points of poor interfacial adhesion and concentrated edge electric field in traditional single insulating coatings are fundamentally solved. The gradient transition layer achieves a smooth transition of the thermal expansion coefficient between the metal electrode and the ceramic insulating layer through compositional gradient, which greatly reduces interfacial thermal stress and effectively avoids coating cracking and peeling. The edge gradient region eliminates the electric field abrupt change at the coating edge through linear thickness gradient, which significantly suppresses the tip discharge phenomenon and improves the working stability and withstand voltage of the laser.

[0082] Step 2: Pre-treat the inner surface of the waveguide electrode to be processed.

[0083] In one specific embodiment, the pretreatment process for the inner surface of the waveguide electrode to be processed is as follows: the waveguide electrode to be processed is placed in an acetone solution for ultrasonic cleaning to remove surface oil and organic residues; then it is placed in anhydrous ethanol for ultrasonic cleaning to remove acetone residues; finally, it is rinsed with deionized water and dried with dry nitrogen gas; for aluminum-based electrodes, if there is an oxide layer on the surface, after cleaning, it is immersed in a 5% to 10% dilute phosphoric acid solution for 30 to 60 seconds for acid pickling activation, and after removing the natural oxide layer, it is immediately rinsed with deionized water and dried to prevent secondary oxidation.

[0084] After cleaning, the surface of the electrode's intended coating area is roughened by using alumina blasting medium to uniformly blast the coating area. After blasting, ultrasonic cleaning is performed again to remove residual blasting medium particles.

[0085] For areas on the electrode that do not require coating, use high-temperature resistant polyimide tape or a custom stainless steel mask to cover the non-coating areas. The masking boundary should be aligned with the processing area boundary defined in step one.

[0086] Step 3: On the electrode surface after the pretreatment in Step 2, an adhesive layer, a gradient transition layer and a ceramic layer are deposited in sequence to form an insulating coating. The edges of the coating are then subjected to a gradual transition treatment so that the coating thickness gradually decreases from the design value at the center to zero at the edge to avoid electric field concentration at the edge.

[0087] In one specific embodiment, the deposition process of the bonding layer and gradient transition layer is as follows: the pre-treated waveguide electrode to be processed is placed in a magnetron sputtering vacuum chamber, and the vacuum is evacuated until the substrate pressure is lower than the set pressure (e.g., 5 × 10⁻⁶). − 4 (Pa), high-purity argon gas is introduced as the working gas, and a high-purity titanium target is used as the sputtering target to deposit a titanium bonding layer on the surface of the electrode substrate.

[0088] After the titanium binder layer is deposited, the gradient transition layer is deposited. The gradient transition layer consists of two phases: titanium and aluminum nitride. The volume fraction of titanium is denoted as... The volume fraction of aluminum nitride is denoted as Using formula (1): and formula (2): ,in , and The equivalent thermal expansion coefficients of the gradient transition layer, aluminum nitride, and titanium at a given titanium volume fraction. , and The equivalent shear modulus of the gradient transition layer, the shear modulus of aluminum nitride, and the shear modulus of titanium. and The bulk modulus of aluminum nitride and the bulk modulus of titanium.

[0089] The total thickness of the gradient transition layer is divided along the thickness direction into... There are three equal-thickness sublayers, with sublayer numbers as follows: , , When, it indicates the side immediately adjacent to the titanium bond layer. When, it indicates the side immediately adjacent to the aluminum nitride ceramic layer.

[0090] The target titanium volume fraction in each sublayer decreases according to a quadratic function: , Represented as the first The volume fraction of titanium corresponding to each sublayer, closer to the titanium binder layer side (i.e. When the content is relatively small, the compositional changes can be gradual because the difference in the coefficients of thermal expansion between titanium atoms is zero, closer to the aluminum nitride ceramic layer side (i.e. The value is close to (At that time), the composition change can be relatively steep because the coefficient of thermal expansion on that side eventually needs to rapidly approach the value of aluminum nitride. When values ​​are taken sequentially, the corresponding values ​​are obtained. ,Will Substituting into formulas (1) and (2), we can obtain the equivalent thermal expansion coefficients corresponding to each sublayer. .

[0091] Adjacent sub-layers and The abrupt change in the coefficient of thermal expansion at the interface is: , Represented as adjacent sub-layers and The abrupt change in the coefficient of thermal expansion at the interface between them. Represented as sub-layer Adjacent sub-layers The equivalent thermal expansion coefficient.

[0092] The interfacial thermal stress caused by the abrupt change in the coefficient of thermal expansion is approximately: , Represented as the first Thermal stress at the interface corresponding to each sublayer and Represented as the first Sub-layers and the first The equivalent elastic modulus of each sublayer Represented as the first The equivalent Poisson ratio of each sublayer It is expressed as the temperature rise when the device is operating, where , Represented as the first Equivalent shear modulus of each sublayer Represented as the first Equivalent bulk modulus of each sublayer .

[0093] Based on a pre-defined upper limit for permissible interfacial thermal stress, the thermal stress at all interfaces... Must meet The value should be less than or equal to the upper limit of the allowable interfacial thermal stress. If this limit is not met, it indicates that the number of sublayers is insufficient, and the stress should be increased. If satisfied, then from Gradually increase Calculate each The corresponding maximum interfacial thermal stress, until it makes ≤ Minimum of the allowable upper limit of interfacial thermal stress The value represents the number of equal-thickness sublayers that divide the total thickness of the gradient transition layer along the thickness direction.

[0094] After determining the target titanium volume fraction for each sublayer, substitute the target titanium volume fraction for each sublayer into the target power ratio formula, which takes the following form: ,in and These represent the sputtering yield of the titanium target and the sputtering yield of the aluminum target under the same operating conditions, respectively. and Represented as the first The sputtering power of the titanium target and the sputtering power of the aluminum target for each sublayer and These are expressed as the atomic masses of titanium and aluminum, respectively. Expressed as the single-atom volume of titanium, It is expressed as the volume of a single molecule of aluminum nitride.

[0095] Obtain the basic nitrogen flow rate and maximum nitrogen flow rate Combined with the sputtering power of the titanium target in each sublayer and aluminum target sputtering power Through the calculation formula: Calculate the first Nitrogen flow rate during sublayer deposition .

[0096] It should be noted that the coefficients of thermal expansion of aluminum nitride and titanium are known material constants, which can be directly obtained from material handbooks or literature. The coefficient of thermal expansion of titanium is 8.6 × 10⁻⁶. -6 Based on standard thermophysical property data for titanium, aluminum nitride has a coefficient of thermal expansion of 4.50 × 10⁻⁶. -6 The standard thermophysical property data of aluminum nitride ceramics are both average values ​​from room temperature to 300℃. The equivalent thermal expansion coefficient of the gradient transition layer under a given titanium volume fraction cannot be directly obtained and needs to be calculated by the equivalent medium model: For any given titanium volume fraction, first look up the bulk modulus and shear modulus of titanium and aluminum nitride from the material handbook, substitute them into formula (2) of the equivalent medium model to solve the equivalent shear modulus, and then substitute them into formula (1) to solve the equivalent thermal expansion coefficient.

[0097] Taking this embodiment as an example, the bulk modulus of titanium (110 GPa) and shear modulus (44 GPa) are derived from the elastic constant data of titanium, while the bulk modulus of aluminum nitride (210 GPa) and shear modulus (128 GPa) are derived from the elastic constant data of aluminum nitride single crystals. Substituting these constants into the model, for a sublayer with a titanium volume fraction of 0.5, the calculated equivalent shear modulus is 68 GPa, and the equivalent coefficient of thermal expansion is 6.2 × 10⁻⁶. -6 This is lower than the linear mixing value of 6.55 × 10⁻⁶. -6 This reflects the constrained thermal expansion effect of harder aluminum nitride compared to softer titanium, and the calculation results are closer to the actual thermal expansion behavior of the composite material.

[0098] The temperature rise during device operation refers to the temperature difference between the plated area on the surface of the waveguide electrode to be processed under radio frequency discharge excitation and the cooling water temperature. This temperature rise is obtained in advance during the coating design stage through thermal simulation calculation or experimental measurement using uncoated original electrodes, and serves as the input parameter for the thermal stress design of the gradient transition layer.

[0099] The shear modulus of titanium and aluminum nitride are known material constants and can be directly obtained from material handbooks or literature. However, the equivalent shear modulus of the gradient transition layer cannot be directly obtained because the gradient transition layer is a non-uniform composite material composed of two phases: titanium and aluminum nitride. Its equivalent shear modulus depends on the volume fraction of the two phases and their respective elastic constants. In practical applications, for any given titanium volume fraction, the equivalent shear modulus of the gradient transition layer can be obtained by substituting the four constants of aluminum nitride shear modulus, titanium shear modulus, aluminum nitride bulk modulus, and titanium bulk modulus obtained from the material handbook into formula (2) of the equivalent medium model for numerical solution.

[0100] The bulk modulus of titanium and aluminum nitride are both known material constants and can be directly obtained from material handbooks or literature.

[0101] Formulas (1) and (2) are both based on the equivalent medium model in the micromechanics of composite materials: Formula (2) is the implicit equation of the equivalent shear modulus, which comes from the Mori-Tanaka equivalent medium theory; Formula (1) is the implicit equation of the equivalent thermal expansion coefficient, which comes from the Turner thermal expansion model. This model considers the influence of the elastic constraints between the phases in the composite material on the thermal expansion behavior. In this scheme, these two formulas are applied to the gradient transition layer composed of titanium and aluminum nitride: For a given titanium volume fraction, the equivalent shear modulus is first solved by formula (2), and then the equivalent shear modulus is substituted into formula (1) to solve the equivalent thermal expansion coefficient, thereby establishing a quantitative correspondence between the material composition (titanium volume fraction) and the thermal expansion coefficient of the gradient transition layer.

[0102] The allowable upper limit of interfacial thermal stress is set based on the interfacial bonding strength between adjacent sublayers of the gradient transition layer. First, the interfacial bonding strength between titanium and aluminum nitride films under actual deposition process conditions is experimentally determined. Specifically, a standard sample of aluminum nitride film deposited on a titanium substrate is prepared, and the critical load is measured using the scratch test. This critical load is then converted to interfacial shear strength, with a typical measured value of approximately 400 MPa. Then, 1 / 5 of the interfacial bonding strength is taken as the allowable upper limit of thermal stress, i.e., the allowable upper limit of interfacial thermal stress equals 80 MPa. The safety factor of 5 is chosen because during long-term operation, the interface not only bears thermal stress but also the combined effects of mechanical vibration stress caused by discharge shocks, gas pressure fluctuation stress, and other loads. A single thermal stress cannot fully cover the load-bearing capacity; sufficient safety margin is required to cope with the superposition of multiple stresses. Taking this embodiment as an example, the scratch test measured the titanium-aluminum nitride interfacial bonding strength as 420 MPa. Taking 1 / 5 yields an allowable upper limit of interfacial thermal stress of 84 MPa.

[0103] The sputtering yields of both titanium and aluminum targets are derived from standard experimental data on ion sputtering yields. This data is determined by three factors: the type of incident ion, the incident energy, and the target material. In magnetron sputtering, argon ions are typically used as the bombarding ion. The relationship between sputtering yield and argon ion incident energy has been systematically measured and summarized into standard curves (such as the Matsunami sputtering yield database). In this scheme, the operating conditions for both titanium and aluminum targets are an argon gas pressure of 0.3 to 0.5 Pa and a sputtering power of 200 to 300 W. Under these conditions, the equivalent energy of argon ions reaching the target surface is approximately 400 to 600 eV. Taking the midpoint of 500 eV as the calibration energy, the sputtering yield of argon ions bombarding a titanium target at 500 eV is found to be 0.51 atoms / ion, and the sputtering yield of argon ions bombarding an aluminum target at 1.05 atoms / ion, according to the sputtering yield database.

[0104] The basic nitrogen flow rate and maximum nitrogen flow rate were obtained through process calibration experiments.

[0105] In one specific embodiment, the deposition process of the aluminum nitride ceramic insulating functional layer is as follows: based on the completed deposition of the titanium bonding layer and gradient transition layer, the electrode clamping posture, deposition coordinate system and vacuum environment remain unchanged to avoid positional offset and interface contamination introduced by secondary clamping.

[0106] The ceramic layer deposition process is divided into three independent stages, each with its own independent reference bias value: a low reference bias is used in the interface nucleation stage to reduce the high-energy ion bombardment energy and promote the uniform nucleation of aluminum nitride nuclei on the gradient transition layer surface, forming a dense and continuous nucleation layer; a high reference bias is used in the columnar crystal growth stage to enhance the bombardment effect of high-energy ions, interrupt the growth of coarse columnar crystals, and refine the grain size; and a medium reference bias is used in the surface planarization stage to reduce the ion bombardment intensity, reduce defects and roughness on the film surface, and obtain a smooth and flat film surface.

[0107] Based on the phased reference bias, an in-situ quartz crystal microbalance (QCM) stress monitoring system is introduced to establish a real-time residual stress feedback closed-loop control mechanism.

[0108] During the ceramic layer deposition process, the QCM system monitors the residual stress value of the film in real time at a sampling frequency of 1Hz. The allowable residual stress fluctuation range for each independent stage is preset. When the real-time monitored residual stress value of the film is greater than the upper limit of the allowable residual stress fluctuation range for the corresponding deposition stage, the control system reduces the amplitude of the pulse bias voltage by a preset first step length until the real-time monitored residual stress value of the film falls back to the allowable range for that stage. When the real-time monitored residual stress value of the film is less than the lower limit of the allowable residual stress fluctuation range for the corresponding deposition stage, the amplitude of the pulse bias voltage is increased by the same preset second step length until the real-time monitored residual stress value of the film falls back to the allowable range for that stage.

[0109] This completes the deposition of the ceramic layer in the flat effective area of ​​the insulating coating. After deposition, the vacuum environment is kept constant, and in-situ performance testing is performed. When all in-situ performance tests are qualified, the vacuum state of the deposition system and the electrode clamping posture are kept constant, and the process of preparing the edge gradient transition zone is started.

[0110] It should be noted that the in-situ quartz crystal microbalance (QCM) stress monitoring system is a high-sensitivity in-situ thin film stress detection device based on the piezoelectric effect of quartz crystal. Without interrupting the deposition process, it monitors the residual stress changes of the thin film deposited on the crystal surface in real time due to lattice mismatch and thermal mismatch. In this scheme, the system serves as the core hardware foundation of the real-time residual stress feedback closed-loop control mechanism. It continuously collects residual stress data of each deposition stage of the aluminum nitride ceramic layer at a sampling frequency of 1Hz, providing a unique quantitative input basis for the dynamic fine-tuning of the pulse bias amplitude.

[0111] The reference bias voltage refers to the bias voltage applied to the waveguide electrode substrate during magnetron sputtering deposition, used to control the intensity of ion bombardment. A low reference bias voltage is a weaker negative bias voltage (in this case, the value is -20 to -30V), a high reference bias voltage is a stronger negative bias voltage (in this case, the value is -50 to -60V), and a medium reference bias voltage is a negative bias voltage between the two (in this case, the value is -35 to -45V). These three values ​​correspond to the states of weak, strong, and moderate ion bombardment intensity, respectively.

[0112] This scheme employs a dual-resonant-frequency quartz crystal microbalance stress monitoring system, which differs from ordinary single-frequency QCMs that can only measure deposition rate and film thickness. This system simultaneously acquires the oscillation frequency changes of the fundamental frequency and the third harmonic of the quartz crystal, and uses the frequency difference separation method to decouple the frequency shift caused by film quality and the frequency shift caused by residual stress. Without interrupting the deposition process, it simultaneously obtains three key parameters of the aluminum nitride ceramic layer: real-time deposition rate, film thickness, and residual stress. Among them, the residual stress data serves as the sole quantitative input for pulse bias closed-loop control.

[0113] The allowable residual stress fluctuation range for each independent stage is determined based on the calculated upper limit of allowable thermal stress at the gradient transition layer interface, the total allowable residual stress design value of the entire coating system, and the functional requirements of each deposition stage combined with the results of pre-experimental verification. For example, in this embodiment, the maximum allowable thermal stress at the gradient transition layer interface has been verified to be 150 MPa, and the total allowable residual stress of the coating system is 500 MPa. Based on this, the following settings are made: In the interface nucleation stage, to avoid damaging the interface bonding of the gradient transition layer, the allowable residual stress fluctuation range is 50~200 MPa; In the columnar crystal growth stage, to balance density and total stress control, the allowable residual stress fluctuation range is 150~300 MPa (the total stress after superimposed interface thermal stress is ≤450 MPa, which is lower than the total allowable upper limit); In the surface smoothing stage, to avoid surface warping affecting subsequent edge gradient processing, the allowable residual stress fluctuation range is 80~150 MPa.

[0114] The first step length and the second step length are set comprehensively based on the sensitivity of the pulse bias voltage to residual stress, the sampling frequency of the QCM system, and the stability requirements of the deposition rate. Since the sensitivity of the influence of bias voltage rise and fall on residual stress is basically symmetrical, the two are set to the same value in engineering to simplify the control system. For example, in this embodiment, it was measured through pre-experiment that for every 5V change in pulse bias voltage, the residual stress of the aluminum nitride film layer changes by 20~30MPa. This change is about 1 / 5 to 1 / 10 of the allowable stress fluctuation range of each stage. This ensures the adjustment accuracy and avoids over-adjustment, while matching the 1Hz sampling frequency of the QCM system to achieve fast response. Therefore, the first step length and the second step length are both set to 5V / step, and this step length matches the maximum adjustment range of bias voltage (±20% of the reference bias voltage of the corresponding stage) to ensure that a single adjustment will not exceed the allowable range.

[0115] The maximum amplitude of the bias voltage adjustment does not exceed ±20% of the reference bias voltage value in the corresponding stage, avoiding the decrease in the density of the film layer caused by excessive adjustment.

[0116] The in-situ performance detection is directly carried out in a vacuum environment without removing the electrode: the actual thickness and thickness uniformity of the flat area of the ceramic layer are measured by an ellipsometer. In this embodiment, the thickness deviation is required to be ≤±3% and the uniformity is ≤±4%; the overall residual stress of the film layer is verified to be ≤300 MPa through the full-range stress data output by the dual-frequency QCM system; the surface resistivity of the film layer is detected by an in-situ four-probe tester, and the resistivity is required to be ≥10 14 Ω・cm. If all indicators meet the requirements, the detection is determined to be qualified.

[0117] In a specific embodiment, the specific process of preparing the edge gradient transition region is as follows: obtain the width of the unilateral edge gradient transition region corresponding to the waveguide electrode to be processed and the rated thickness of the flat area of the ceramic layer , define the distance from any position in the gradient region to the edge of the flat area [[ID=十五]],利用公式: , calculate the target thickness at any position in the gradient region , when equals 0, , when 时, .

[0118] Under constant process parameters, the coating thickness is proportional to the deposition time, that is , where represents the measured deposition rate of the ceramic layer, represents the position where the horizontal distance from the edge of the flat area is , and its corresponding effective deposition time.

[0119] When the mask moves outward from the edge of the flat area at a constant speed , the effective deposition time is the time required for the mask to move from the position to the outer edge of the gradient region, that is, the total deposition time minus the time for the mask to move to the position , that is , combined with the target thickness , when 时, , substitute to get: , and then get .

[0120] After passing the in-situ performance test, while maintaining the deposition vacuum, substrate temperature, argon / nitrogen flow rate, and target power, the high-precision linear displacement stage is driven to move the movable metal mask to the edge of the flat effective area defined in step one. The alignment error between the mask edge and the edge of the flat area is ≤10μm. The deposition power supply is then started, and the deposition proceeds at the calculated speed. Drive the mask to move at a constant speed to the outside of the gradient region until the mask moves to the outer edge of the gradient region. Turn off the deposition power supply to complete the preparation of the single-sided edge gradient transition region. Keep all process parameters unchanged (process parameters include but are not limited to the vacuum degree of the deposition system, substrate temperature, argon flow rate, nitrogen flow rate and target power), and repeat the above process to complete the preparation of the edge gradient transition region on the other side of the electrode.

[0121] It should be noted that the width of the gradient transition zone on one side is derived and determined in step one based on the equivalent spot radius of the waveguide electrode and the effective coverage width of the insulating coating, and verified by optical field calibration; the rated thickness of the flat zone of the ceramic layer is determined based on the rated operating voltage of the laser, and the correspondence between its deposition rate and thickness has been verified by in-situ dual-frequency QCM system.

[0122] The flat region refers to the uniformly thick aluminum nitride ceramic insulating layer region on the inner surface of the waveguide electrode, corresponding to the core area of ​​the laser field. The gradient region refers to the transition region outside the flat region, extending from the edge of the flat region to the edge of the electrode, where the thickness linearly decreases from the nominal value to 0.

[0123] It should also be noted that the closer a point is to the flat area, the shorter the time it is blocked by the mask and the longer the time it is exposed, resulting in a thicker coating; conversely, the farther a point is from the flat area, the longer the time it is blocked and the shorter the time it is exposed, resulting in a thinner coating.

[0124] An aluminum nitride ceramic layer deposition process employing a staged differentiated reference bias combined with in-situ quartz crystal microbalance (QCM) stress closed-loop control achieves precise control over the coating's microstructure and residual stress. Through a three-stage process—low bias to promote uniform nucleation during the interface nucleation stage, high bias to refine grains during the columnar crystal growth stage, and medium bias to reduce roughness during the surface smoothing stage—the resulting ceramic layer exhibits high density and fine, uniform grains. Furthermore, the introduction of a QCM real-time stress monitoring and pulse bias dynamic adjustment mechanism controls the residual stress of the coating within the design limits, further enhancing the coating's mechanical strength and insulation reliability.

[0125] Step 4: Perform vacuum annealing on the prepared insulating coating to release residual stress, and verify whether the coating thickness uniformity, insulation performance, stress state and edge gradient linearity meet the design requirements through offline testing.

[0126] In one specific embodiment, the process of verifying whether the coating thickness uniformity, insulation performance, stress state, and edge gradient linearity meet the design requirements through offline detection is as follows: The waveguide electrode after vacuum annealing is removed from the deposition system, and a laser confocal microscope is used to perform a full-domain thickness scan of the flat area and the gradient area along the optical field coordinate system established in step one to verify whether the thickness uniformity deviation in the flat area meets the design requirements; a high-precision insulation resistance tester is used to test the insulation resistance of the coating, and a high-voltage breakdown tester is used to test whether the coating breakdown voltage is ≥ 1.5 times the rated operating voltage of the laser to verify whether the coating insulation performance meets the design requirements; an X-ray stress analyzer is used to detect whether the absolute value of the residual stress of the coating meets the design requirements.

[0127] Once all test items meet the design requirements, the coating is deemed qualified, and the process proceeds to step five, waveguide electrode assembly and resonant cavity precision debugging. If any item fails to meet the standard, the process returns to step three to redo the insulation coating preparation.

[0128] It should be noted that when verifying the thickness uniformity deviation of the flat area, the actual thickness of each measuring point in the flat area measured by the laser confocal microscope is compared with the design rated thickness, and the thickness deviation of each measuring point is calculated. If the thickness uniformity deviation of all measuring points is within the design allowable range, the requirement is deemed to be met; otherwise, it is not met. When verifying the insulation performance of the coating, the measured insulation resistance value is compared with the design insulation resistance threshold, and the measured breakdown voltage is compared with 1.5 times the rated operating voltage of the laser. If the insulation resistance is not lower than the design threshold and the breakdown voltage is ≥ 1.5 times the rated operating voltage of the laser, the requirement is deemed to be met; otherwise, it is not met. When detecting the residual stress of the coating, the absolute value of the measured residual stress of the coating is compared with the design allowable stress threshold. If the absolute value of the residual stress is not greater than the design threshold, the requirement is deemed to be met; otherwise, it is not met.

[0129] During the fabrication of the edge gradient transition region, by calculating a constant mask moving speed and driving the mask to move at a uniform speed, the coating thickness is linearly reduced from the rated value in the flat area to zero at the edge. This avoids the problems of low precision and poor consistency in traditional manual polishing or photolithography processes, effectively suppresses the concentration of the edge electric field, prevents gas breakdown, and improves the stability of device operation.

[0130] Step 5: Measure the equivalent capacitance introduced by the insulating coating, calculate and adjust the compensation inductance value accordingly, construct an impedance matching compensation network, and dynamically adjust it by real-time monitoring of VSWR and discharge voltage fluctuations to ensure effective coupling of RF power and stable discharge.

[0131] In one specific embodiment, the process of constructing the impedance matching compensation network is as follows: using an impedance analyzer at the rated operating frequency of the laser RF excitation source. Impedance tests were performed on the waveguide electrodes fabricated after the completion of the transition layer, flat insulating region, and edge gradient region to extract the equivalent parallel capacitance between the waveguide electrodes introduced by the coating layer in the presence of the coating layer. Simultaneously, it uses the laser excitation module's nominal excitation source, and the output transmission line's standard characteristic impedance... .

[0132] Based on the rated excitation frequency, using the formula: Calculate the operating angular frequency of the radio frequency excitation. .

[0133] Combining the operating angular frequency and the equivalent parallel capacitance between electrodes, using the formula: The series compensation inductor for matching capacitive loads of the electrodes is derived. .

[0134] Based on the calculated series compensation inductor used to match the capacitive load of the electrode. Select an adjustable inductor and pair it with an auxiliary matching capacitor to complete the initial assembly of the impedance matching compensation network.

[0135] It should be noted that the rated operating frequency of the laser RF excitation source is an inherent design parameter of the excitation module. The nominal rated frequency value can be obtained by directly referring to the technical manual of the RF source equipment manufacturer, or it can be measured and calibrated by a frequency meter under the laser's no-load excitation state. This frequency is the standard operating frequency that matches the discharge requirements of the resonant cavity.

[0136] An impedance analyzer was used to perform two-port impedance tests on a pair of waveguide electrodes with a complete insulating coating at the rated operating frequency of the laser. The overall structure formed by the electrodes and the coating was equivalent to a parallel RC load model. The impedance amplitude and phase data between the electrodes were collected by the instrument, and the equivalent parallel capacitance between the electrodes was directly extracted by the built-in fitting algorithm.

[0137] The standard characteristic impedance of the excitation source output transmission line is an inherent design parameter of the RF excitation system and transmission cable, directly taken from the factory technical specifications of the RF excitation module and its matching transmission line. Gas laser RF transmission systems generally use 50 ohms as the standard characteristic impedance, which can be directly used as a fixed reference for matching calculations.

[0138] Based on the calculated theoretical value of the series compensation inductance, select an adjustable inductor with an adjustment range covering the calculated value and a ±10% adjustment margin. For example, in this implementation case, the calculated compensation inductance value is 12.6nH, so select an RF adjustable inductor with a nominal adjustment range of 10~15nH. During initial assembly, adjust the inductance value directly to the calculated value.

[0139] A small-capacity, high-precision adjustable ceramic capacitor is connected in parallel across the series compensation inductor as an auxiliary matching capacitor. In this implementation case, a fine-tuning capacitor of 0.2~2.0pF is selected to match it. In addition to the equivalent parallel capacitance introduced by the insulating plating, the actual electrode system also has parasitic parameters such as electrode leads and transmission connectors. The inductor alone cannot achieve complete impedance matching. The addition of a small-capacity auxiliary capacitor compensates for the overall impedance and further improves the matching accuracy of the matching network.

[0140] In one specific embodiment, dynamic debugging is performed by real-time monitoring of VSWR and discharge voltage fluctuations. The specific process is as follows: Based on the impedance matching compensation network that has completed the initial assembly and the waveguide electrode to be processed with a complete insulating coating, the overall load is connected to the laser RF excitation transmission circuit and the resonant cavity. The rated output state of the RF excitation source is used as the debugging benchmark to perform dynamic optimization debugging of impedance matching.

[0141] Obtain the maximum allowable VSWR, rated discharge voltage, and maximum allowable fluctuation of discharge voltage for the waveguide electrode to be processed.

[0142] Turn on the RF excitation source and load the rated output power. The VSWR of the current waveguide electrode system is collected in real time by the VSWR tester, and the real-time discharge voltage of the electrode gap is collected by the discharge voltage acquisition module. The rated discharge voltage of the waveguide electrode is subtracted from the real-time discharge voltage of the electrode gap, and the absolute value of the difference is calculated to obtain the real-time fluctuation amplitude of the current discharge voltage.

[0143] The current system VSWR is compared with the maximum allowable VSWR, and the current real-time fluctuation amplitude of the discharge voltage is compared with the maximum allowable fluctuation value of the discharge voltage. If the current waveguide electrode system VSWR is less than or equal to the maximum allowable VSWR and the current real-time fluctuation amplitude of the discharge voltage is less than or equal to the maximum allowable fluctuation value of the discharge voltage, then the impedance matching compensation network is deemed to be successfully debugged and the waveguide electrode system can enter a stable working state. Otherwise, the assembled adjustable compensation inductor and auxiliary matching capacitor are iteratively adjusted in small steps. After each adjustment, the corresponding parameters are re-acquired and the fluctuation value is calculated until the impedance matching compensation network is successfully debugged.

[0144] It should be noted that the maximum allowable standing wave ratio of the waveguide electrode is an inherent design specification of the laser RF excitation system, which is directly taken from the overall system design technical documents or industry general specifications. In this implementation case, based on the stable discharge requirements of the gas laser, the value is no greater than 1.1.

[0145] The rated discharge voltage of the waveguide electrode is calculated and determined by core design parameters such as the discharge gap of the resonant cavity, the working gas pressure, and the excitation power. The nominal value is obtained by referring to the design drawings of the electrode and the cavity. The maximum allowable fluctuation amplitude of the discharge voltage is calculated and determined based on the discharge stability requirements, at ±2% of the rated discharge voltage. This is a commonly used fluctuation control value in this field.

[0146] The specific process of iteratively adjusting the assembled adjustable compensation inductor and auxiliary matching capacitor in small steps is as follows: During the debugging process, only a small amount of adjustment is made to the parameters of the adjustable compensation inductor and auxiliary matching capacitor each time. After adjustment, the system VSWR and discharge voltage data are re-acquired, and the optimal matching state is gradually approached based on the monitoring results. For example, in this implementation case, the inductance value of the adjustable inductor is increased or decreased by no more than 0.5nH and the capacitance value of the auxiliary capacitor is increased or decreased by no more than 0.1pF each time. After completing one adjustment, the parameters are immediately detected. This process is repeated iteratively until the requirements are met.

[0147] The waveguide electrode system refers to an integrated discharge load system consisting of the waveguide electrode to be processed after the insulating coating has been completed, the impedance matching compensation network, and the radio frequency transmission connection line.

[0148] During the impedance matching debugging process, by measuring the equivalent capacitance introduced by the coating, calculating the series compensation inductance and constructing a matching network, and combining it with a dynamic debugging mechanism that monitors the standing wave ratio and discharge voltage fluctuations in real time, the problems of low RF power coupling efficiency and large discharge voltage fluctuations in traditional processes are solved, ensuring effective RF power coupling and uniform and stable discharge.

[0149] Step 6: Assemble the waveguide electrode system, after impedance matching and debugging, into the laser unit and perform integrated debugging and comprehensive performance verification.

[0150] In one specific embodiment, the process of overall system integration and comprehensive performance verification is as follows: The waveguide electrode system with completed impedance matching is assembled into the laser resonant cavity structure, and connected to the cooling, gas path, and control unit. Under rated working gas pressure, excitation power, and cooling conditions, the entire system is continuously powered on for integration and testing. The stability of laser output power, discharge uniformity, beam quality, and long-term working reliability are tested sequentially, and the change curves of key parameters such as VSWR, discharge voltage, and output optical power over working time are recorded. If all parameters consistently meet the design specifications and there are no phenomena such as arcing, mode skipping, or coating abnormalities, the preparation and assembly of this batch of waveguide electrodes are deemed qualified, and the entire system can be put into formal use. If performance is found to be substandard, the impedance matching status and coating quality are checked, and the process is returned to the corresponding process for reprocessing.

[0151] Standardization and controllability have been achieved from positioning and coating deposition to performance testing. This includes thermal stress back-calculation of the number of gradient transition layer sublayers, three-stage bias control and in-situ stress monitoring of ceramic layer deposition, as well as offline comprehensive testing and verification, which significantly improves process consistency and meets the needs of industrial mass production.

[0152] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement any step of a waveguide electrode coating process.

[0153] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A waveguide electrode coating process method, characterized in that, include: S1. Construct a two-dimensional coordinate system corresponding to the waveguide electrode to be processed, calculate the actual position of the beam waist on the inner surface of the waveguide electrode to be processed, and calculate the total offset between the actual position and the theoretical position of the beam waist. The positioning is determined based on the total offset. If it is qualified, the insulating coating processing area is delineated with the actual position of the beam waist as the core. S2. Based on the area processed by the insulating coating, pre-treat the inner surface of the waveguide electrode to be processed; An insulating coating is formed by depositing a titanium bonding layer, a gradient transition layer and a ceramic layer on the inner surface of the pretreated electrode. The gradient transition layer is divided into equal-thickness sub-layers, and the nitrogen flow rate corresponding to the deposition of each equal-thickness sub-layer is calculated. S3. Based on the completed deposition of the titanium bonding layer and gradient transition layer, the ceramic layer deposition process is divided into three independent stages, including the interface nucleation stage, the columnar crystal growth stage and the surface planarization stage. Combined with the pre-set allowable residual stress fluctuation range for each stage, the ceramic layer deposition process is evaluated. S4. Prepare the edge gradient transition region of the corresponding electrode and verify whether the coating performance meets the design requirements; S5. Measure the equivalent capacitance introduced by the insulating coating, calculate and adjust the compensation inductance value, construct the impedance matching compensation network, and monitor the standing wave ratio and discharge voltage fluctuations in real time for dynamic debugging until the impedance matching compensation network is qualified.

2. The waveguide electrode coating process according to claim 1, characterized in that, The specific process for calculating the total offset between the actual and theoretical positions of the beam waist includes: A unique two-dimensional reference coordinate system is constructed with the lower left corner vertex of the inner surface of the waveguide electrode to be processed as the origin, the electrode length extension direction as the X-axis, and the electrode width extension direction as the Y-axis. A full-domain grid scan is performed on the waveguide discharge region on the inner surface of the electrode along the X and Y axes, and the coordinates and corresponding light field intensity of each scan point are collected in real time. By combining the coordinates and light field intensity of each scanning point, fitting calculations are used to solve the beam waist center coordinates, beam waist spot radius in the horizontal axis direction, and beam waist spot radius in the vertical axis direction corresponding to the waveguide electrode to be processed. By obtaining the theoretical beam waist center coordinates and combining them with the beam waist center coordinates corresponding to the waveguide electrode to be processed, the total offset between the actual beam waist center and the theoretical beam waist center is calculated.

3. The waveguide electrode coating process according to claim 2, characterized in that, The specific process for determining whether the positioning is qualified based on the total offset includes: Obtain the coverage width of the insulating coating in the direction of the corresponding electrode width of the waveguide electrode to be processed, and the width of one side of the gradient transition zone at the edge of the coating, and calculate the equivalent coverage width of the electric field region corresponding to the waveguide electrode to be processed. By combining the beam waist spot radius in the horizontal axis direction and the beam waist spot radius in the vertical axis direction, the equivalent spot radius at the center of the beam waist is calculated. By combining the equivalent coverage width of the electric field region corresponding to the waveguide electrode to be processed and the equivalent spot radius at the beam waist center, the maximum allowable offset threshold between the actual beam waist center and the theoretical beam waist center is calculated. The positioning is judged to be qualified by combining the total offset between the actual beam waist center and the theoretical beam waist center with the maximum allowable offset threshold.

4. The waveguide electrode coating process according to claim 3, characterized in that, The specific process of analyzing nitrogen flow rates during the deposition of equal-thickness sublayers includes: The total thickness of the gradient transition layer is divided into equal-thickness sub-layers along the thickness direction, and the titanium volume fraction corresponding to each sub-layer is calculated. Obtain the equivalent thermal expansion coefficients of the gradient transition layer, aluminum nitride, and titanium. Obtain the equivalent shear modulus of the gradient transition layer, the shear modulus of aluminum nitride, and the shear modulus of titanium, as well as the bulk modulus of aluminum nitride and titanium. Combine the titanium volume fraction of each sublayer to calculate the equivalent thermal expansion coefficient of each sublayer. Based on the equivalent thermal expansion coefficient, calculate the abrupt change in thermal expansion coefficient between adjacent sublayers; The equivalent Poisson's ratio of each sublayer is calculated by combining the equivalent shear modulus and the equivalent bulk modulus. By combining the abrupt change in the coefficient of thermal expansion between adjacent sublayers and the temperature rise during electrode operation, the thermal stress at the corresponding interface of each sublayer is calculated. Based on the preset allowable upper limit of interfacial thermal stress, the number of equal-thickness sub-layers divided along the thickness direction of the total thickness of the gradient transition layer is analyzed. To obtain the sputtering yield of the target material, based on the titanium volume fraction of each sublayer, combined with the atomic mass of titanium, the atomic mass of aluminum, the single atom volume of titanium, and the single molecule volume of aluminum nitride, the sputtering power of the titanium target and the sputtering power of the aluminum target for each sublayer are calculated. The basic nitrogen flow rate and the maximum nitrogen flow rate are obtained, and then the nitrogen flow rate during the deposition of each sublayer is calculated.

5. The waveguide electrode coating process according to claim 1, characterized in that, The deposition process of the ceramic layer is as follows: The ceramic layer deposition was performed in three stages, with each stage using a reference bias that matched the corresponding deposition requirements. During the deposition process, the residual stress of the film layer is acquired in real time through an in-situ stress monitoring device. Based on the monitoring data, the pulse bias voltage is adjusted in a closed loop to control the residual stress within a preset range. After deposition, the vacuum and clamping conditions are kept unchanged, and the coating is tested in situ. After passing the test, the edge gradient transition zone of the coating is prepared in a vacuum environment.

6. The waveguide electrode coating process according to claim 5, characterized in that, The specific process for preparing the edge gradient transition region is as follows: Obtain the width of the single-sided edge gradient transition region and the rated thickness of the flat region of the ceramic layer corresponding to the waveguide electrode to be processed. Define the distance L from any position of the gradient region to the edge of the flat region and determine the target thickness at that position. Among them, when When the target thickness is 0, it equals the rated thickness of the flat region of the ceramic layer. When the target thickness is equal to the width of the gradient transition zone on one side of the edge, the target thickness is equal to 0. By combining the measured deposition rate of the ceramic layer with the effective deposition time corresponding to the position at a horizontal distance L from the edge of the flat area, the target thickness equation and the actual deposition thickness equation are solved simultaneously to obtain a constant mask moving speed. Drive the mask at a constant speed from the edge of the flat region to the outside of the gradient region to complete the preparation of the single-sided edge gradient transition region.

7. The waveguide electrode coating process according to claim 6, characterized in that, The specific process for verifying whether the coating performance meets the design requirements is as follows: Offline comprehensive testing was conducted on the insulating coating after vacuum annealing. The test items included coating thickness uniformity, insulation performance, residual stress, and edge gradient linearity. Once all test items meet the design requirements, the coating is deemed qualified and the process moves to waveguide electrode assembly and resonant cavity precision debugging. If any item fails to meet the standard, the insulation coating preparation is repeated.

8. The waveguide electrode coating process according to claim 7, characterized in that, The specific process of constructing an impedance matching compensation network is as follows: At the rated operating frequency of the laser RF excitation source, impedance tests were performed on the waveguide electrodes that had completed the preparation of the transition layer, flat insulation region and edge gradient region. The equivalent parallel capacitance between the electrodes introduced by the coating layer was extracted, and the standard characteristic impedance of the output transmission line of the laser excitation module was obtained. Calculate the operating angular frequency of the radio frequency excitation based on the rated excitation frequency; Combining the operating angular frequency and the equivalent parallel capacitance between electrodes, the series compensation inductor required to match the capacitive load of the electrodes is derived. Based on the calculated series compensation inductance, an adjustable inductor is selected and paired with an auxiliary matching capacitor to complete the initial assembly of the impedance matching compensation network.

9. The waveguide electrode coating process according to claim 8, characterized in that, Dynamic adjustment is performed by real-time monitoring of VSWR and discharge voltage fluctuations. The specific process is as follows: Connect the assembled waveguide electrode system to the laser RF excitation transmission circuit and resonant cavity, using the rated output of the RF excitation source as the debugging benchmark; Obtain the maximum allowable VSWR of the waveguide electrode system, the rated discharge voltage of the electrode, and the maximum allowable fluctuation amplitude of the discharge voltage. Turn on the radio frequency excitation source and apply the rated power. Real-time acquisition of the waveguide electrode system standing wave ratio and the real-time discharge voltage of the electrode gap is obtained. The absolute value of the difference between the real-time discharge voltage and the rated discharge voltage is taken to obtain the real-time fluctuation amplitude of the discharge voltage. The current system VSWR is compared with the maximum allowable VSWR, and the current real-time fluctuation amplitude of the discharge voltage is compared with the maximum allowable fluctuation value of the discharge voltage. If both meet the threshold requirements, the debugging is qualified. Otherwise, the adjustable compensation inductor and auxiliary matching capacitor are iteratively adjusted in small steps, and the comparison is repeated until the debugging is qualified.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 9.

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