Diamond polishing apparatus and method with adaptive energy density and overlap rate

Abstract

The present application belongs to the technical field of laser processing. An energy density and overlap rate adaptive diamond polishing device and method are proposed. By integrating multiple lens groups, square cross-section homogenization optical fibers and a three-dimensional motion platform, a square flat-top focal spot size of 280-880 mu m is continuously adjustable, and the scanning speed and overlap rate are synchronously linked and controlled. The present application does not require expensive devices such as spatial light modulators. Through lens motor coordinated adjustment and closed-loop control, it can adapt to different ablation threshold diamonds, improve polishing uniformity and efficiency, reduce equipment cost and maintenance difficulty, and is suitable for high-quality preparation of high-voltage and high-frequency diamond devices.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, and in particular to a diamond polishing apparatus and method with adaptive energy density and overlap rate. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Diamond, as a typical ultrawide bandgap semiconductor material, exhibits irreplaceable application potential in the fabrication of high-voltage, high-temperature, high-frequency, high-power, and radiation-resistant devices due to its superior properties such as ultrawide bandgap, high thermal conductivity, high carrier mobility, and high breakdown electric field. With the innovation of laser technology and motion control technology, ultrafast laser precision machining has become a core technology for diamond surface treatment. Its principle involves focusing an ultrashort pulse laser onto the surface or subsurface of diamond, converting light energy into heat energy through nonlinear absorption. When the energy density exceeds the material modification threshold, a phase transition or selective removal occurs in the focal region, resulting in micro-regional modification. By controlling the laser to scan along a preset path using a precision motion system, layer-by-layer controllable removal of the material surface can be achieved, effectively reducing surface roughness and damage, providing crucial surface treatment support for the high-quality fabrication of diamond devices.

[0004] However, current conventional processes for laser polishing diamonds mostly use unshaped circular Gaussian spots for polishing, such as... Figure 1 As shown, surface uniformity and flattening are achieved by adjusting the beam overlap rate. In practice, circular Gaussian beams inherently suffer from uneven energy distribution, significantly increasing polishing difficulty and reducing polishing quality. Specifically, the beam spacing typically does not exceed the beam diameter, leading to a trade-off between laser scanning speed and scanning line spacing. This results in bottlenecks such as long processing time and low efficiency, severely limiting the industrial application of laser polishing technology.

[0005] To address the issue of processing time, a common strategy is to increase laser scanning speed. However, rapid scanning reduces the spot overlap rate and increases the spot spacing, leading to uneven energy distribution and consequently affecting surface quality. Another approach is to increase the scanning line spacing; however, there is an extreme limit to the line spacing, meaning that excessively large spacing leads to a decrease in longitudinal overlap rate, reduced energy uniformity, and consequently, lower polishing quality.

[0006] Recently, researchers proposed a device and method for polishing square flat-top laser spots using a spatial light modulator. This involves a spot shaping module (containing a beam expander and multiple sub-transfer modules) working in conjunction with a spot modulation module. After the laser beam is matched by the beam expander, it is guided by the sub-transfer modules to the modulation module to achieve square flat-top laser spot modulation. However, this approach has significant drawbacks: the device structure is complex, requiring multiple sub-transfer modules, resulting in a large device size, which is not conducive to industrial deployment; the spot modulation module is expensive and has a low damage threshold, leading to high subsequent maintenance and component procurement costs, making it difficult to meet the needs of industrial applications. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a diamond polishing apparatus and method with adaptive energy density and overlap rate. It achieves fully controllable operation from fiber coupling input, laser beam homogenization and shaping, fiber output alignment to final focused scanning processing, and can form a uniform and stable square flat-topped spot distribution on the diamond surface, while ensuring high consistency in the polishing process.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a diamond polishing apparatus with adaptive energy density and overlap rate.

[0010] A diamond polishing device with adaptive energy density and overlap rate includes a laser, a first lens group, a square cross-section homogenizing fiber, a second lens group, a third lens group, and a three-dimensional motion platform.

[0011] The laser is used to output pulsed laser. The first lens group includes two lenses with adjustable spacing, which are used to adjust the beam parameters incident on the square cross-section homogenizing fiber. The square cross-section homogenizing fiber is used to shape the Gaussian beam into a square flat-top beam.

[0012] The second lens group includes two axially adjustable lenses for collimating and expanding the square flat-top beam. The third lens group includes a 45° mirror and at least two axially adjustable lenses for deflecting the optical path and focusing the collimated and expanded square flat-top beam onto the surface of the diamond sample, forming a square flat-top focal spot with an equivalent size that is continuously adjustable in the range of 280μm to 880μm.

[0013] The three-dimensional motion platform is used to carry the diamond sample and control the scanning motion of the diamond sample in the XY plane and the position adjustment in the Z-axis direction;

[0014] Under the condition of constant laser output power, the equivalent size of the square flat-top focal spot is changed by adjusting the axial spacing of each lens in the first lens group, the second lens group and the third lens group to adaptively adjust the energy density acting on the diamond sample surface; the three-dimensional motion platform adaptively adjusts the scanning speed and the spacing between adjacent scanning lines according to the equivalent size, so that adjacent focal spots achieve a preset overlap rate in the horizontal and vertical directions.

[0015] In one implementation of the first aspect of the present invention, the first lens group adjusts the incident angle, divergence angle and equivalent Rayleigh length of the beam incident on the square cross-section homogenized optical fiber by adjusting the axial distance between the two lenses.

[0016] In one implementation of the first aspect of the present invention, the second lens group and the third lens group together constitute a focal spot size control unit. Through the coordinated axial displacement of the four lenses, the equivalent size of the focal spot is continuously adjusted while maintaining the characteristics of a square flat-top beam.

[0017] In one implementation of the first aspect of the present invention, the 45° reflector in the third lens group is used to refract the light path to a vertical direction to irradiate the diamond sample, and the first and second adjustment lenses on the front and rear sides of the 45° reflector are respectively adjusted by independent motors to compensate for the optical axis offset caused by the light path refraction.

[0018] As a further limitation of the first aspect of the present invention, the adjustment of the focal position is accomplished through the Z-axis of the three-dimensional motion platform, and the second control lens remains fixed during the processing.

[0019] In one implementation of the first aspect of the present invention, the three-dimensional motion platform integrates a position feedback unit for real-time monitoring of the diamond sample position and correction of the scanning trajectory, and the overlap rate of adjacent focal spots in the lateral and longitudinal directions is independently set according to the ablation threshold of the diamond material.

[0020] In one implementation of the first aspect of the present invention, square flat-topped focal spots are arranged in a row and column trajectory regularity on the surface of the diamond sample, and uniform coverage of the processing area is achieved by controlling the scanning speed and the line spacing.

[0021] In one implementation of the first aspect of the present invention, a mapping table of equivalent size of the focal spot and laser energy density is pre-stored. After setting the target energy density, the mapping table is automatically queried, and the first lens group, the second lens group and the third lens group are driven to adjust to the corresponding lens spacing to generate a matching square flat-top focal spot.

[0022] In one implementation of the first aspect of the present invention, an online monitoring module is further included, which is used to collect the surface morphology or ablation depth of the processed area in real time. The three-dimensional motion platform dynamically corrects the line spacing or scanning speed of the subsequent scanning path according to the feedback data of the online monitoring module, so as to realize closed-loop adaptive control of the overlap rate.

[0023] Secondly, the present invention provides a diamond polishing method with adaptive energy density and overlap rate.

[0024] A diamond polishing method with adaptive energy density and overlap ratio, utilizing the diamond polishing apparatus with adaptive energy density and overlap ratio according to the first aspect of the present invention, includes the following process:

[0025] Turn on the laser and output pulsed laser light with the set power;

[0026] Adjust the axial spacing between the two lenses in the first lens group to match the numerical aperture of the square cross-section homogenized optical fiber.

[0027] A square flat-top beam is obtained after being shaped by a square cross-section homogenized fiber, and then passes through the second lens group and the third lens group in sequence;

[0028] By adjusting the axial position of each lens in the second and third lens groups, the square flat-top beam is focused into a square flat-top focal spot with an equivalent size adjustable in the range of 280μm to 880μm.

[0029] Under the condition of constant laser power, the corresponding equivalent size is selected according to the target energy density;

[0030] Based on the selected equivalent size, the scanning speed of the three-dimensional motion platform and the spacing between adjacent scanning lines are calculated and set so that adjacent focal spots achieve a preset overlap rate in the horizontal and vertical directions.

[0031] The three-dimensional motion platform is controlled to drive the diamond sample to scan according to the set parameters and complete the polishing process.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention integrates multiple adjustable-spacing lenses with square-section homogenizing optical fibers to construct a polishing device that can generate continuously adjustable square flat-top focal spots without a spatial light modulator. This fundamentally overcomes the problem of inconsistent surface removal caused by uneven energy distribution in traditional Gaussian spots, while avoiding the drawbacks of relying on complex optical paths or high-cost modulation devices to achieve flat-top spots. Under constant laser power, the equivalent size of the focal spot can be precisely controlled by adjusting the spacing of each lens group through motor drive, thereby adaptively matching the ablation threshold of different diamond materials. With the linkage adjustment of scanning speed and line spacing by a three-dimensional motion platform, adjacent focal spots can achieve controllable overlap or close splicing, effectively solving the core contradiction that has long restricted the synergistic improvement of laser polishing efficiency and quality: "increasing the scanning speed will reduce the overlap rate, and increasing the line spacing will weaken the uniformity."

[0034] This invention significantly broadens the process window and material adaptability of diamond laser polishing. Since the focal spot size can be continuously adjusted within a wide range, the device can flexibly set the optimal energy density for diamond samples with different doping types, crystal orientations, or defect densities. This avoids problems such as unexpected phase transitions caused by excessive energy or insufficient removal caused by excessively low energy. This adaptive capability allows the same equipment to stably process a variety of diamond-based device precursors without the need for frequent replacement of optical components or recalibration of the entire optical path parameters. This greatly improves process robustness and production line flexibility, providing reliable surface treatment support for the large-scale application of diamond in high-voltage, high-frequency, and other high-end semiconductor fields.

[0035] This invention achieves high uniformity and repeatability in the removal of diamond surface materials. The square flat-topped focal spot itself has the characteristics of clear edges and flat energy distribution. Combined with a precisely controlled lateral and longitudinal overlap strategy, it ensures the consistency of energy deposition throughout the processing area, effectively suppressing defects such as periodic stripes, central overburning, or underpolishing at the edges that are easily generated by traditional Gaussian spot scanning. At the same time, the beam shaping process is completed by a square cross-section homogenizing fiber, which has high output light field stability and is not affected by external vibration or temperature drift. In addition, the position of the lens group is precisely controlled by a motor, which makes the starting conditions of each processing highly reproducible, thereby ensuring the consistency of polishing quality between batches and meeting the stringent requirements for surface morphology control in precision device manufacturing.

[0036] This invention possesses excellent engineering practicality and industrialization prospects. It abandons expensive and fragile optical components such as spatial light modulators and majority transfer modules, instead employing conventional lenses, motors, and square optical fibers to construct an all-solid-state optical path. This results in a compact structure, easy maintenance, and controllable costs. All key parameters (such as focal spot size, scanning speed, and line spacing) can be automatically set via software commands, making operation simple and easy to integrate into automated production lines. Furthermore, Z-axis focusing is performed by a motion platform, avoiding optical axis disturbances caused by moving the focusing lens, further improving the long-term stability of the system. This provides a practical technical path for ultrafast laser precision polishing technology to move from the laboratory to the industrial field.

[0037] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0038] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0039] Figure 1 This is a schematic diagram of a circular Gaussian spot scanning provided in the background art of this invention;

[0040] Figure 2 A schematic diagram of an energy density and overlap rate adaptive diamond polishing apparatus provided as an exemplary embodiment of the present invention;

[0041] Figure 3 A schematic diagram of the movement position of the motor-controlled lens group is provided as an exemplary embodiment of the present invention, wherein, Figure 3 (a) in the diagram is a schematic diagram of the first lens motor and the second lens motor being close together (with the third lens and the fourth lens in the middle). Figure 3 (b) is a schematic diagram showing the first lens motor and the second lens motor moving away from each other (with the third and fourth lenses in the center). Figure 3 (c) in the diagram is a schematic diagram of the first lens motor and the second lens motor being close together (the third lens and the fourth lens are located on opposite sides). Figure 3 (d) in the diagram is a schematic diagram of the first lens motor and the second lens motor moving away from each other (the third lens and the fourth lens are located on the side that are close to each other).

[0042] Figure 4 A schematic diagram of a square flat-top light spot scanning processing path is provided for an exemplary embodiment of the present invention;

[0043] Figure 5 A schematic diagram of a square flat-top spot overlapping scanning processing path is provided as an exemplary embodiment of the present invention;

[0044] Figure 6 A schematic diagram of a small-sized square flat-top spot scanning processing path is provided as an exemplary embodiment of the present invention;

[0045] Among them, 100 is the laser; 200 is the first lens group; 210 is the first control lens; 220 is the second control lens; 300 is the square cross-section homogenizing fiber; 400 is the second lens group; 410 is the third control lens; 420 is the fourth control lens; 430 is the first lens motor; 440 is the second lens motor; 450 is the transmission device; 500 is the third lens group; 510 is the fifth control lens; 520 is the 45° reflector; 530 is the sixth control lens; 600 is the diamond sample; and 700 is the three-dimensional motion platform. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0047] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0048] This invention provides a diamond polishing device with adaptive energy density and overlap rate, whose overall architecture is designed to achieve high uniformity, high efficiency, and high adaptability in laser surface treatment. For example... Figure 2 and Figure 3 As shown, the device mainly includes a laser 100, a first lens group 200, a square cross-section homogenizing fiber 300, a second lens group 400, a third lens group 500, a diamond sample 600, and a three-dimensional motion platform 700. These components are integrated through precision optomechanical processes to form a complete process chain from laser generation, beam shaping, focal spot control to sample scanning. This enables continuous adjustment of the square flat-top focal spot size without relying on a spatial light modulator or multiple transfer module, and simultaneously matches scanning parameters to achieve dual adaptive energy density and overlap rate.

[0049] The working process begins with laser 100, which is preferably a picosecond or femtosecond ultrafast pulsed laser. Its output wavelength can be selected according to the absorption characteristics of the diamond material, with typical values ​​including 1030 nm, 515 nm, or 343 nm. The original beam output by laser 100 usually has a Gaussian distribution, characterized by high energy at the center and rapid attenuation at the edges. If used directly for polishing, it can easily lead to overburning in the central area and insufficient edge removal, resulting in periodic stripes or local roughness abrupt changes on the surface.

[0050] To overcome this problem, this invention introduces a multi-stage beam control mechanism. First, the beam is guided into a first lens group 200. The first lens group 200 consists of a first control lens 210 and a second control lens 220, arranged sequentially along the optical axis, with their spacing continuously adjustable via an external drive mechanism. In this embodiment, the first control lens 210 and the second control lens 220 are mounted on the same slide rail support. At least one lens (e.g., the second control lens 220) is connected to a stepper motor or servo motor, driven by a precision lead screw or linear module to move along the optical axis, thereby changing the relative distance between the two lenses. This change in spacing directly affects the divergence angle, beam waist position, and equivalent Rayleigh length of the incident beam. When this parameter is precisely controlled, the numerical aperture and mode distribution of the outgoing beam can be precisely matched to the receiving conditions of the subsequent square cross-section homogenizing fiber 300, thereby maximizing coupling efficiency, reducing energy loss, and ensuring that the light field entering the fiber has good spatial coherence and stability. This pre-shaping step is crucial for the subsequent homogenization effect and is a prerequisite for ensuring the final focal spot quality.

[0051] The beam, after being controlled by the first lens group 200, enters the square-section homogenized fiber 300. The square-section homogenized fiber 300 is a specially designed multimode fiber with a core cross-section that is square or approximately square, with side lengths typically on the order of hundreds of micrometers. When the Gaussian beam is coupled into the fiber from the circular input end, it undergoes multiple total internal reflections within the fiber, resulting in strong coupling and energy exchange between different modes. Due to the constraint of the square boundary on the light field, the energy originally concentrated at the center is forced to diffuse towards the four corners. After a sufficient transmission length, the light intensity distribution at the output end tends to be highly uniform, forming a typical "top-hat" morphology with steep edges and a clear outline. It is worth noting that this process is entirely based on the physical properties of the optical fiber itself, requiring no additional spatial light modulator, diffractive optical elements, or complex feedback control systems. Therefore, it is simple in structure, low in cost, and has strong anti-interference capabilities, making it particularly suitable for long-term stable operation in industrial environments. The output end of the square cross-section homogenized fiber 300 directly serves as the source of the square flat-top beam. Its size is determined by the fiber core diameter and is usually fixed, but its far-field divergence characteristics can still be further modulated by the upstream optical system. Specifically… Figure 4 , Figure 5 and Figure 6 The diagrams show the processing paths for scanning a square flat-top spot, overlapping square flat-top spot, and small square flat-top spot.

[0052] The square-topped beam output from the square-section homogenizing fiber 300 then enters the second lens group 400. The second lens group 400 is one of the core control units for achieving continuously adjustable focal spot size in this invention. Its structure includes a third control lens 410, a fourth control lens 420, a first lens motor 430, a second lens motor 440, and a transmission device 450. The third control lens 410 is located on the beam incident side and mainly performs collimation; the fourth control lens 420 is located on the exit side, forming a variable magnification telescope system together with the third control lens 410. Crucially, the third control lens 410 and the fourth control lens 420 are not fixedly installed, but are independently driven by the first lens motor 430 and the second lens motor 440, respectively, and are linked through the transmission device 450. The transmission device 450 can be a rack and pinion, a synchronous belt, or a linkage mechanism. Its function is to ensure that the two lenses maintain a specific proportional relationship of motion during adjustment, thereby maintaining beam collimation or achieving controllable beam expansion while changing the overall system length. By precisely controlling the displacement of the first lens motor 430 and the second lens motor 440, the axial distance between the third control lens 410 and the fourth control lens 420 can be continuously adjusted, thereby changing the beam diameter and divergence angle of the emitted beam. This adjustment directly determines the size of the focal spot after subsequent focusing. Increasing the distance usually leads to an increase in the beam expansion ratio and a larger focal spot; conversely, the focal spot shrinks. Therefore, the second lens group 400 constitutes a key link in the coarse and medium adjustment of the focal spot size.

[0053] As an optional implementation, the focal spot size adjustment algorithm can be used to calculate the lens spacing adjustment amount, as shown in the formula:

[0054] (1);

[0055] in, Represented by the equivalent size of the target focal spot ( ); The reference focal spot size represents the initial spacing of the lens group. ); This represents the lens spacing adjustment amount of the second lens group ( ); The lens spacing adjustment amount (mm) represents the third lens group 500; and The lens spacing to spot size conversion factor ( By establishing a quantitative relationship between lens spacing and focal spot size, continuous and precise control of focal spot size was achieved.

[0056] Next, the beam output from the second lens group 400 enters the third lens group 500. The third lens group 500 (including the fifth adjustment lens 510, the 45° reflector 520, and the sixth adjustment lens 530) performs the dual tasks of optical path deflection and fine-tuning of the focal spot. The 45° reflector 520 deflects the originally horizontally propagating beam by 90 degrees, causing it to illuminate the surface of the diamond sample 600 below in a vertical direction. This layout helps save lateral space in the equipment and facilitates the integration of sample observation or online monitoring systems. However, optical path deflection introduces optical axis shift and aberration disturbances. To compensate for these effects, the third lens group 500 has the fifth adjustment lens 510 and the sixth adjustment lens 530 respectively located on the front and rear sides of the 45° reflector 520. These two lenses are driven by independent precision motors and can be displaced at the micrometer level along the optical axis. By adjusting the position of these two lenses, not only can the optical axis drift caused by reflection be corrected, but the wavefront curvature of the beam can also be fine-tuned, thereby achieving precise control over the final focused spot size.

[0057] To avoid optical axis misalignment caused by the coupling of the spacing adjustment between the second lens group 400 and the third lens group 500, in one optional viewing method, a lens group spacing collaborative adjustment algorithm can be simultaneously invoked, with the following formula:

[0058] (2);

[0059] in, Represents the optical axis alignment compensation constant (mm).

[0060] More importantly, the last lens in the third lens group 500 actually functions as the end-focusing lens, and its focal length and position together determine the working distance and focal spot shape. Therefore, this invention does not treat the "end-focusing lens" as a separate element from the third lens group 500, but rather embeds its function within the third lens group 500, thus avoiding structural redundancy and optical path complexity.

[0061] After being controlled by the third lens group 500, the laser beam is finally focused onto the surface of the diamond sample 600, forming a square flat-topped focal spot with uniform energy distribution and sharp edges. The equivalent size of this focal spot (defined as the diameter of a circle with equal area) can be continuously adjusted within the range of 280μm to 880μm, covering various process requirements from fine finishing to efficient rough polishing. With the output power of the laser 100 remaining constant, changes in the focal spot size directly lead to changes in the laser energy density acting per unit area; the smaller the focal spot, the higher the energy density; the larger the focal spot, the lower the energy density.

[0062] Optionally, an adaptive matching algorithm for laser energy density can be invoked to calculate the current energy density in real time to match the material ablation threshold. The formula is as follows:

[0063] (3);

[0064] in, Represented by the laser energy density of the processed surface ( ); Represents laser output power (W); Represents the scanning speed of the 3D motion platform ( ); Represents the scan line spacing (mm); The equivalent size of the focal spot (mm) is represented by the energy density, which is calculated in real time based on the focal spot size to ensure that it matches the ablation threshold range of the diamond material.

[0065] This feature allows the operator to flexibly set an appropriate energy density based on the specific material of the diamond sample 600 (such as single crystal / polycrystalline, doping type, defect density, etc.) and its ablation threshold, avoiding graphitization phase transition or microcracks caused by excessive energy, and also preventing the material from being ineffectively removed due to insufficient energy.

[0066] Optionally, to address the energy attenuation problem at the edge of the light spot, a light spot energy uniformity compensation algorithm can be used to correct the energy distribution. The formula is as follows:

[0067] (4);

[0068] in, Represents the radius of the light spot Actual energy uniformity at the location (%) Represents the energy uniformity at the center of the light spot (%). Represents the edge energy decay coefficient; Represents the distance from a point within the light spot to the center ( This compensates for energy attenuation at the edge of the light spot, corrects the energy distribution model, and improves polishing uniformity.

[0069] The diamond sample 600 is securely mounted on the three-dimensional motion platform 700, which has three degrees of freedom: X-axis, Y-axis, and Z-axis, all controlled by high-precision servo motors or piezoelectric actuators. The Z-axis is used to fine-tune the position of the diamond sample 600 along the optical axis, ensuring its surface is always on the optimal plane for laser focusing, thus achieving precise focusing.

[0070] Optionally, a focus offset correction algorithm for the machining surface can be invoked to automatically calculate based on changes in the focal spot size. Shaft correction amount, formula is:

[0071] (5);

[0072] in, represent Axis focus correction amount ( ); Represents the focal length of the focusing lens ( ); Represents the change in focal spot size ( Automatically corrects based on changes in focal spot size. The axis position ensures that the focus is always at the optimal machining surface.

[0073] shaft and The axis coordinates with the scanning motion of the diamond sample 600 in the horizontal plane, covering the processing area line by line according to a preset trajectory (such as raster scanning, spiral scanning, or a custom path). The key innovation of this invention is that the three-dimensional motion platform 700 does not operate independently, but is deeply linked with the optical control system. Specifically, when the user selects the target energy density, the control system first deduces the required equivalent size of the focal spot based on the pre-stored physical model or calibration curve, and generates target position commands for each lens in the first lens group 200, the second lens group 400, and the third lens group 500 accordingly, driving the corresponding motors to complete the optical path adjustment. At the same time, the system automatically calculates the optimal scanning speed and the distance between adjacent scanning lines based on the focal spot size, so that adjacent focal spots can achieve a preset overlap rate (e.g., 30%, 50%, or close splicing) in both the horizontal (inter-row) and vertical (inter-column) directions.

[0074] Optionally, in other implementations, the horizontal spot overlap rate calculation algorithm and the vertical spot overlap rate calculation method are called respectively, and the horizontal overlap rate is:

[0075] (6);

[0076] In the formula, The lateral spot overlap rate (%) is used to quantitatively characterize the degree of spot overlap between adjacent scan lines, providing a parameter basis for uniform polishing.

[0077] Vertical overlap is:

[0078] (7);

[0079] in, The longitudinal beam overlap rate is %. The laser pulse period (s) is used to correlate the scanning speed with the pulse period, precisely control the longitudinal overlap rate, and eliminate processing stripes.

[0080] This linkage mechanism completely resolves the inherent contradictions in traditional methods, such as "increasing scanning speed inevitably reduces overlap" or "increasing line spacing inevitably weakens uniformity," thus achieving synergistic optimization of efficiency and quality.

[0081] Optionally, in some other implementations, a material removal rate prediction method can be invoked to predict the polishing efficiency based on energy density and overlap rate parameters, as shown in the formula:

[0082] (8);

[0083] in, diamond material removal rate ( ); Material removal coefficient ( A quantitative model of process parameters and material removal rate was established, enabling accurate prediction of polishing efficiency.

[0084] It is worth emphasizing that the entire device abandons the spatial light modulator (SLM), digital micromirror device (DMD), or multi-beam splitter modules commonly found in existing technologies. All beam shaping and control functions are achieved through conventional lenses, motors, and square cross-section homogenizing fiber 300. This not only significantly reduces system cost and maintenance difficulty but also significantly improves long-term operational reliability. In addition, the adjustment of the focal position is entirely completed by the Z-axis of the three-dimensional motion platform 700, and the end optical element (i.e., the third lens group 500) remains fixed during processing, avoiding optical axis jitter or mechanical backlash errors that may be caused by moving the focusing lens, further ensuring processing accuracy.

[0085] In practice, users can input target process parameters (such as desired surface roughness, material removal depth, processing time, etc.) through a human-machine interface. The system automatically matches the optimal energy density and overlap strategy and generates a complete sequence of control commands. The entire process requires no manual intervention in optical path adjustment, greatly reducing the operational threshold. Simultaneously, the device can be optionally equipped with an online monitoring module (such as a confocal microscope, white light interferometer, or ablation depth sensor) to collect real-time data on the surface morphology or material removal status of the processed area and feed the data back to the control system. Based on this, the control system dynamically corrects the line spacing or speed of subsequent scanning paths, achieving closed-loop adaptive control of the overlap rate, further improving processing consistency and robustness.

[0086] In summary, this invention, through the ingenious integration of an adjustable lens group and a square-section homogenizing fiber 300, constructs a diamond laser polishing system that is structurally simple, flexibly adjustable, and stable in performance. It not only fundamentally solves the quality problems caused by uneven energy in the Gaussian spot, but also achieves dual self-adaptation of energy density and overlap rate through intelligent linkage between the focal spot size and scanning parameters. This balances processing efficiency, surface quality, and process adaptability, providing a reliable and economical surface treatment solution for the large-scale application of diamond in high-end fields such as semiconductors, quantum sensing, and high-power electronics.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A diamond polishing apparatus with adaptive energy density and overlap rate, characterized in that, It includes a laser, a first lens group, a square cross-section homogenized optical fiber, a second lens group, a third lens group, and a three-dimensional motion platform; The laser is used to output pulsed laser. The first lens group includes two lenses with adjustable spacing, which are used to adjust the beam parameters incident on the square cross-section homogenizing fiber. The square cross-section homogenizing fiber is used to shape the Gaussian beam into a square flat-top beam. The second lens group includes two axially adjustable lenses for collimating and expanding the square flat-top beam. The third lens group includes a 45° reflecting mirror and at least two axially adjustable lenses for deflecting the optical path and focusing the collimated and expanded square flat-top beam onto the diamond sample surface. The second and third lens groups together constitute a focal spot size control unit. Through the coordinated axial displacement of the four lenses, the equivalent size of the focal spot can be continuously adjusted while maintaining the characteristics of the square flat-top beam, forming a square flat-top focal spot with an equivalent size continuously adjustable in the range of 280μm to 880μm. The three-dimensional motion platform is used to carry the diamond sample and control the scanning motion of the diamond sample in the XY plane and the position adjustment in the Z-axis direction. Under the condition of constant laser output power, the equivalent size of the square flat-top focal spot is changed by adjusting the axial spacing of each lens in the first lens group, the second lens group and the third lens group to adaptively adjust the energy density acting on the surface of the diamond sample. The three-dimensional motion platform adaptively adjusts the scanning speed and the distance between adjacent scanning lines according to the equivalent size, so that adjacent focal spots achieve a preset overlap rate in the horizontal and vertical directions. The three-dimensional motion platform integrates a position feedback unit for real-time monitoring of the diamond sample position and correction of the scanning trajectory. The overlap rate of adjacent focal spots in the lateral and longitudinal directions is independently set according to the ablation threshold of the diamond material.

2. The diamond polishing apparatus with adaptive energy density and overlap rate as described in claim 1, characterized in that, The first lens group adjusts the axial spacing between the two lenses to synchronously control the incident angle, divergence angle, and equivalent Rayleigh length of the beam incident on the square cross-section homogenized optical fiber.

3. The diamond polishing apparatus with adaptive energy density and overlap rate as described in claim 1, characterized in that, The 45° reflector in the third lens group is used to refract the light path to a vertical direction to illuminate the diamond sample. The first and second adjustment lenses on the front and rear sides of the 45° reflector are adjusted by independent motors to compensate for the optical axis offset caused by the light path refraction.

4. The diamond polishing apparatus with adaptive energy density and overlap rate as described in claim 3, characterized in that, The focus position is adjusted via the Z-axis of the three-dimensional motion platform, and the second control lens remains fixed during the processing.

5. The diamond polishing apparatus with adaptive energy density and overlap rate as described in claim 1, characterized in that, The square flat-topped focal spots are arranged in a row and column pattern on the surface of the diamond sample, and uniform coverage of the processing area is achieved by controlling the scanning speed and the line spacing.

6. The diamond polishing apparatus with adaptive energy density and overlap rate as described in claim 1, characterized in that, A pre-stored mapping table of equivalent focal spot size and laser energy density is used. After setting the target energy density, the mapping table is automatically queried, and the first lens group, the second lens group, and the third lens group are driven to adjust to the corresponding lens spacing to generate a matching square flat-top focal spot.

7. The diamond polishing apparatus with adaptive energy density and overlap rate as described in claim 1, characterized in that, It also includes an online monitoring module for real-time acquisition of the surface morphology or ablation depth of the processed area. The three-dimensional motion platform dynamically corrects the line spacing or scanning speed of the subsequent scanning path based on the feedback data from the online monitoring module, thereby achieving closed-loop adaptive control of the overlap rate.

8. A diamond polishing method with adaptive energy density and overlap ratio, utilizing the diamond polishing apparatus with adaptive energy density and overlap ratio as described in any one of claims 1 to 7, characterized in that, Includes the following processes: Turn on the laser and output pulsed laser light with the set power; Adjust the axial spacing between the two lenses in the first lens group to match the numerical aperture of the square cross-section homogenized optical fiber. A square flat-top beam is obtained after being shaped by a square cross-section homogenized fiber, and then passes through the second lens group and the third lens group in sequence; By adjusting the axial position of each lens in the second and third lens groups, the square flat-top beam is focused into a square flat-top focal spot with an equivalent size adjustable in the range of 280μm to 880μm. Under the condition of constant laser power, the corresponding equivalent size is selected according to the target energy density; Based on the selected equivalent size, the scanning speed of the three-dimensional motion platform and the spacing between adjacent scanning lines are calculated and set so that adjacent focal spots achieve a preset overlap rate in the horizontal and vertical directions. The three-dimensional motion platform is controlled to drive the diamond sample to scan according to the set parameters and complete the polishing process.

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