Optical system and optical processing apparatus

Abstract

An embodiment of the present application provides an optical system and an optical processing device, which comprises a light source module, a polarization modulation module, a micromirror array and an objective assembly. The light source module is used for outputting femtosecond laser pulses. The polarization modulation module is used for receiving and modulating the polarization state of the femtosecond laser pulses into a circular polarization state. The micromirror array is used for receiving and spatially modulating the femtosecond laser pulses in the circular polarization state to generate different patterns. The objective assembly is used for receiving and focusing the patterns to the surface of a sample. In this way, the femtosecond laser pulses passing through the polarization modulation module have the same polarization state in each direction, which makes the absorption rate and working efficiency of different positions of the sample M consistent in the laser processing process, thereby facilitating the improvement of the quality and effect of processing. Moreover, the micromirror array is sensitive to the polarization state, and the design is also conducive to avoiding the energy loss and non-uniformity caused by polarization, and is conducive to further improving the uniformity and processing precision of processing.

Description

Technical Field

[0001] This application relates to the field of laser processing technology, and in particular, to an optical system and optical processing equipment. Background Technology

[0002] With the development of science and technology, laser processing technology has long permeated all aspects of modern life, from the electronic products we use to medical and health care, and then to daily consumer goods. Its emergence has greatly improved the quality, convenience and safety of our lives.

[0003] In particular, laser processing technology has played an indispensable role in the development of photolithography. Due to the high manufacturing cost of photomasks, multiple photomasks are often required during use. Digital micromirror arrays (DMIs) can dynamically generate digital photomasks, replacing traditional photomasks and reducing costs. Laser processing technology has significantly improved the flexibility, efficiency, and customization capabilities of photomask fabrication.

[0004] However, due to the continuous output of high-energy laser light, the heat accumulation effect on the sample surface is significant, which can easily lead to thermal damage such as heat-affected zones, melting and resolidification, or even microcracks on the sample surface. This severely restricts the processing quality and accuracy on high-precision, heat-sensitive materials (such as semiconductor components and flexible polymers). Utility Model Content

[0005] In view of this, this application provides an optical system and optical processing equipment, aiming to solve the problem that it is difficult to improve the accuracy of non-mask manufacturing using current laser processing technology.

[0006] In a first aspect, one embodiment of this application provides an optical system including a light source module, a polarization modulation module, a micromirror array, and an objective lens assembly. The light source module outputs femtosecond laser pulses. The polarization modulation module receives and modulates the polarization state of the femtosecond laser pulses into a circularly polarized state. The micromirror array receives and spatially modulates the circularly polarized femtosecond laser pulses to generate different patterns. The objective lens assembly receives and focuses the patterns onto the surface of a sample.

[0007] As one possible implementation, the optical system also includes a beam shaping module, which receives and redistributes the energy of circularly polarized femtosecond laser pulses to obtain femtosecond laser pulses with uniform energy distribution. The femtosecond laser pulses with uniform energy distribution are then irradiated onto the surface of the sample after passing through the micromirror array and objective lens assembly.

[0008] As one possible implementation, the optical system also includes a spatial filtering-beam expander, which is used to filter stray light from circularly polarized femtosecond laser pulses and expand the diameter of the filtered femtosecond laser pulses so that the expanded femtosecond laser pulses, after passing through the beam shaping module, micromirror array and objective lens assembly, illuminate the surface of the sample.

[0009] As one possible implementation, the spatial filtering-beam expander assembly sequentially includes a first lens, a pinhole filter, and a second lens. The rear focal plane of the first lens and the front focal plane of the second lens coincide in position. The pinhole filter is located at the position of the rear focal plane of the first lens, and the focal length of the second lens is greater than that of the first lens.

[0010] As one possible implementation, the polarization modulation module includes an electro-optic modulator.

[0011] As one possible implementation, the objective lens assembly includes a tube and an objective lens, wherein the front focal plane of the tube and the rear focal plane of the objective lens are optically conjugate.

[0012] As one possible implementation, the optical system also includes an image sensor, which is coaxially arranged with the objective lens assembly for observing patterns on the sample surface.

[0013] In one possible implementation, the optical system also includes a first lens, a pinhole filter, a second lens, an aspherical homogenizer, a tube mirror, and an objective lens. The back focal plane of the first lens coincides with the front focal plane of the second lens. The pinhole filter is located at the position of the back focal plane of the first lens, and the focal length of the second lens is greater than that of the first lens. The front focal plane of the tube mirror and the back focal plane of the objective lens are optically conjugate. After the femtosecond laser pulse passes through the electro-optic modulator, the first lens, the pinhole filter, the second lens, the aspherical homogenizer, the micromirror array, the tube mirror, and the objective lens, it is focused onto the surface of the sample.

[0014] Secondly, one embodiment of this application provides an optical processing apparatus, which includes an optical system and a controller as described above. Based on control commands, the controller controls a light source module to output femtosecond laser pulses and adjusts the polarization state of the femtosecond laser pulses to circularly polarized femtosecond laser pulses, so that the circularly polarized femtosecond laser pulses pass through a micromirror array to generate different patterns, which are then focused onto the surface of the sample. The controller also controls an image sensor to observe the patterns on the sample surface.

[0015] As one possible implementation, the optical processing equipment also includes a displacement stage on which the sample is placed to focus the pattern onto the sample surface. A controller is also used to control the displacement stage to move the sample.

[0016] In this way, the light source module outputs linearly polarized femtosecond laser pulses (i.e., linearly polarized light) S0. These pulses are then modulated by the polarization modulation module into circularly polarized femtosecond laser pulses (i.e., circularly polarized light) S1. The circularly polarized light then passes through the micromirror array 30 to obtain different (mask) patterns. Finally, the objective lens assembly 40 focuses these patterns onto the surface of the sample M, generating a specific pattern. Thus, the femtosecond laser pulses after polarization modulation have the same polarization state in all directions. This ensures that the absorption rate and efficiency are consistent across different locations on the sample M during laser processing, thereby improving processing quality and effectiveness. Furthermore, the micromirror array is highly sensitive to polarization; this design also helps avoid energy loss and inhomogeneity caused by polarization, further improving processing uniformity and accuracy.

[0017] Furthermore, the synergistic effect of femtosecond laser pulses and micromirror arrays forms a maskless dynamic direct-write system. On one hand, femtosecond laser pulses can achieve nanoscale processing precision, while the micromirror array can act as a "digital mask," controlling the working state of each micromirror in real time to generate different patterns. This helps reduce the high cost of physical mask fabrication, improves mask fabrication efficiency, and facilitates personalized customization, increasing the flexibility of mask fabrication and enabling rapid iterative design. Moreover, by precisely controlling the laser energy reflected from each micromirror to each pixel on the sample M, it is possible to achieve complex three-dimensional patterns in a single exposure without the need for layered scanning. Furthermore, since the micromirror array is a purely solid-state electronic device, compared to microelectromechanical systems (MEMS), this application has no moving mechanical parts, thus improving response speed and lifespan. Attached Figure Description

[0018] It should be understood that the following figures only show some embodiments of this application and should not be regarded as a limitation on the scope.

[0019] It should be understood that the same or similar reference numerals are used in the accompanying drawings to denote the same or similar elements.

[0020] It should be understood that the accompanying drawings are only schematic, and the dimensions and scales of the elements in the drawings are not necessarily precise.

[0021] Figure 1 This is a schematic diagram of the structure of an optical system provided in an embodiment of this application.

[0022] Figure 2 This is a schematic diagram of the structure of an optical system provided in another embodiment of this application.

[0023] Figure 3 This is a schematic diagram of the structure of an optical system provided in another embodiment of this application.

[0024] Figure 4 This is a schematic diagram of the structure of a spatial filtering-beam expander provided in an embodiment of this application.

[0025] Figure 5 This is a schematic diagram of an objective lens assembly provided in one embodiment of this application.

[0026] Figure 6 This is a schematic diagram of the structure of an optical system provided in another embodiment of this application.

[0027] Figure 7 This is a schematic diagram of the structure of an optical processing system provided in an embodiment of this application.

[0028] Figure 8 This is a schematic diagram of an objective lens assembly provided in another embodiment of this application. Detailed Implementation

[0029] The embodiments of this application are described below with reference to the accompanying drawings. It should be understood that there are various ways to implement this application, and it should not be construed as being limited to the embodiments described herein. The embodiments described herein are only for a more thorough and clear understanding of this application.

[0030] A photomask, an indispensable core tool in photolithography, is typically a thin, opaque film deposited on a transparent substrate. Through electron beam lithography and chemical etching, patterns from a database are precisely transferred to the transparent substrate, forming the designed circuit pattern. This enables subsequent photolithography to transfer the circuit pattern onto a silicon wafer to form the desired chip. (Prerequisite.)

[0031] Typically, masks include physical masks and traditional photomasks. Physical masks have a simple fabrication process and relatively low cost, but due to limitations in machining capabilities and the gap between the mask and the substrate, the minimum linewidth is usually on the order of micrometers or larger, failing to meet the requirements of highly integrated circuits. Furthermore, it is difficult to fabricate complex and high-density patterns and is not suitable for mass production. Traditional photomasks offer higher resolution and precision, and have strong production capabilities. This is because photomasks are fabricated through direct electron beam writing, enabling the creation of patterns with feature sizes smaller than the wavelength of light, and complex patterns can be formed in a single exposure, resulting in extremely high production efficiency. However, their manufacturing cost is high, the fabrication cycle is long, and each mask corresponds to a fixed design; once the design is changed, the mask is discarded and needs to be remade. Therefore, this fabrication method has poor flexibility, low efficiency, and is unsuitable for customized applications.

[0032] Laser processing technology, as an advanced "tool," enables ultra-high precision processing at the micrometer level because the laser beam can be focused into an extremely small spot, making it suitable for precision applications such as semiconductor chips. Picosecond and femtosecond laser pulses, in particular, have extremely short pulse durations, allowing energy to be absorbed instantaneously at the electron absorption level within the material, thus avoiding thermal damage and microcracks to surrounding materials through heat conduction, achieving so-called "cold processing." Furthermore, laser processing technology offers advantages such as tool-free processing, deformation-free processing, high-efficiency switching, and rapid processing, making it a key enabling technology for advancing high-end technologies and playing an indispensable role in the development of photolithography.

[0033] In view of this, refer to Figures 1 to 8 This application provides an optical system 100, which sequentially includes a light source module 10, a polarization modulation module 20, a micromirror array 30, and an objective lens assembly 40. Thus, the laser pulses output from the light source module 10 sequentially pass through the polarization modulation module 20, the micromirror array 30, and the objective lens assembly 40 before irradiating the surface of the sample.

[0034] refer to Figure 1 The light source module 10 is used to output a femtosecond laser pulse S0, which is linearly polarized. The light source module 10 can be a femtosecond laser 11, and the femtosecond laser pulse S0 output by the femtosecond laser 11 is typically a Gaussian beam, meaning the light intensity distribution in the plane perpendicular to the propagation direction follows a Gaussian function (i.e., bright in the middle, dark at the edges, shaped like a circular "bell curve"), thus possessing good beam quality. Furthermore, the polarization state of the femtosecond laser pulse output by the femtosecond laser is typically linearly polarized, meaning the electric field vector of the light wave vibrates in a fixed direction, which is beneficial for generation (e.g., mode-locking), amplification, and further applications (e.g., nonlinear transformation, precision control). Of course, the polarization state of the femtosecond laser pulse S0 can also be other polarization states, such as elliptical polarization or circular polarization, etc., which are not specifically limited here.

[0035] Continue to refer to Figure 1 The polarization modulation module 20 is used to receive and modulate the linear polarization state of the femtosecond laser pulse S0 into a circular polarization state to obtain a circularly polarized femtosecond laser pulse S1. Of course, the polarization modulation module 20 can also modulate femtosecond laser pulses of other polarizations into a circular polarization state. If the femtosecond laser pulse output by the light source module 10 is circularly polarized, no further modulation is required.

[0036] It can be understood that circularly polarized light refers to light whose electric field vector remains constant in magnitude, but whose endpoint rotates at the speed of light along a spiral as the light propagates through space. In other words, viewed from the direction of light propagation, the light wave propagates forward in a spiral shape. Because the light field vector of circularly polarized light has the same polarization state in all directions, interference caused by "polarization dependence" is eliminated. Therefore, when a laser pulse interacts with a material, its effect is consistent in all directions. For example, in laser processing, when linearly polarized light irradiates a material surface, its absorption rate and cutting efficiency vary with the angle between the laser polarization direction and the scanning direction, leading to uneven cutting edges and inconsistent depths. When circularly polarized light irradiates a material surface, its absorption rate and cutting efficiency are the same in all directions; therefore, the material can be processed uniformly, and the cutting edges are smooth and of consistent depth. There are many ways to implement polarization modulation modules, such as mechanical waveplates (e.g., quarter-wave plates), acousto-optic modulators, and electro-optic modulators.

[0037] refer to Figures 1 to 3 The micromirror array 30 is used to receive and spatially modulate the circularly polarized femtosecond laser pulse S1 to generate different patterns. Specifically, the micromirror array 30 forms different arrangements according to different preset patterns, thereby obtaining different patterns. The micromirror array 30 may include multiple tiny mirror arrays arranged in a certain pattern. Each mirror can be individually controlled in its state (e.g., on or off) to form different patterns and illuminate the surface of the sample M. In this way, the laser pulse can be modulated into hundreds of thousands or even millions of pixels at once, forming a complete pattern in one go, and reflecting these points onto the surface of the sample M in one go. Compared to the traditional point-to-point scanning method, this greatly improves processing efficiency. Moreover, the state can be controlled according to different patterns, thus improving the flexibility of the pattern. In one example, reference... Figure 6 The micromirror array 30 can be a digital micromirror device (DMD) 31.

[0038] refer to Figures 1 to 3 The objective lens assembly 40 is used to receive and focus a pattern onto the surface of the sample M, so that the pattern is "transferred" to the surface of the sample M to form a specific pattern. The objective lens assembly 40 has the function of converging light, which is beneficial for further improving power density and pattern resolution. In one example, the objective lens assembly may include a combination of convex and concave lenses, which can not only eliminate optical aberrations but also further converge the pattern. In one example, the objective lens assembly 40 may also include multiple convex lenses. No specific limitation is made here.

[0039] In this way, the light source module outputs a linearly polarized femtosecond laser pulse (i.e., linearly polarized light) S0. This linearly polarized femtosecond laser pulse S0 is modulated into a circularly polarized femtosecond laser pulse (i.e., circularly polarized light) S1 after passing through the polarization modulation module 20. Subsequently, the circularly polarized light passes through the micromirror array 30 to obtain different patterns. Finally, the objective lens assembly 40 focuses the pattern onto the surface of the sample M, generating a specific pattern. Thus, the femtosecond laser pulses after passing through the polarization modulation module have the same polarization state in all directions. This ensures that the absorption rate and working efficiency are consistent at different positions of the sample M during laser processing, thereby improving the processing quality and effect. Furthermore, the micromirror array is highly sensitive to polarization state; this design also helps to avoid energy loss and inhomogeneity caused by polarization, further improving the uniformity and accuracy of the processing.

[0040] Furthermore, the synergistic effect of femtosecond laser pulses and micromirror arrays forms a maskless dynamic direct-write system. On one hand, femtosecond laser pulses enable nanoscale processing precision, while the micromirror array acts as a "digital mask," controlling the working state of each micromirror in real time to generate different patterns. This not only helps reduce the high cost of physical mask fabrication and improves its efficiency but also facilitates personalized customization, increasing the flexibility of mask fabrication and enabling rapid iterative design. Moreover, by precisely controlling the laser energy reflected from each micromirror to each pixel on the sample M, it is possible to achieve complex three-dimensional patterns in a single exposure without the need for layered scanning. Furthermore, since the micromirror array is a purely solid-state electronic device, it has no moving mechanical parts compared to laser galvanometer scanning systems, thus improving response speed and lifespan.

[0041] It should be noted that the maskless dynamic direct writing system uses digital graphics to dynamically generate patterns, thus replacing the function of a photomask. By controlling the micromirror array with a computer or controller to change the exposure pattern, it is possible to easily generate grayscale patterns, curved surface patterns, variable patterns, and other structures that are difficult to achieve with traditional photomasks.

[0042] In one example, reference Figure 6The polarization modulation module 20 may include an electro-optic modulator 21. After passing through the electro-optic modulator 21, the femtosecond laser pulse outputs a circularly polarized femtosecond laser pulse. It can be understood that the electro-optic modulator (EOM) utilizes the Pöckels effect (i.e., the refractive index changes linearly with the applied electric field) of an electro-optic crystal (such as lithium niobate LiNbO3). When the laser passes through this crystal, its two orthogonal polarization components will generate a phase difference due to the change in refractive index, thereby changing the polarization state of the emitted light. By controlling the voltage, this phase difference can be precisely controlled, thus achieving precise control of the polarization state. Using an electro-optic modulator facilitates nanosecond-level switching of the laser polarization state, thereby improving the control accuracy of the laser pulse's polarization state. Furthermore, it offers many advantages such as low damage, programmable exposure, and easy integration.

[0043] In one example, reference Figure 6 The objective lens assembly 40 may include a tube lens 41 and an objective lens 42. The front focal plane of the tube lens 41 and the rear focal plane of the objective lens 42 are optically conjugate, satisfying the conditions for telecentric imaging (i.e., the focal length of the tube lens matches the interpupillary distance of the objective lens), so that the pattern is "transferred" to the surface of the sample M to form a specific pattern, which is beneficial for achieving sub-micron focusing. The tube lens 41 may be a first convex lens 45, and the objective lens 42 may be an infinity-corrected second convex lens 46 with a large numerical aperture (e.g., NA ≥ 0.7) and a working distance ≥ 2 mm. The tube lens 41 needs to be used in conjunction with the infinity-corrected objective lens 42 to build an infinity-corrected optical system. In the infinity-corrected optical system, light rays passing through the objective lens 42 from the object surface are not imaged by the objective lens, but instead enter the imaging lens as a parallel beam at infinity, forming an intermediate image. Specifically, the front focal plane of the first convex lens 45 and the rear focal plane of the second convex lens 46 are optically conjugate, which can reduce the beam of the laser pulse to concentrate the energy of the laser pulse spot.

[0044] refer to Figure 8 The size of the beam before entering the tube lens 41 is the same as the size of the beam after passing through the digital micromirror device (DMD) 31. The infinitely corrected objective lens assembly 40 formed by the combination of the tube lens 41 and the objective lens 42 increases the size of the beam, so that it can be irradiated to different positions on the surface of the sample M in the form of beam splitting.

[0045] refer to Figure 2The optical system 100 may further include a beam shaping module 50, which receives and redistributes the energy of the circularly polarized femtosecond laser pulse S1 to obtain a femtosecond laser pulse with uniform energy distribution. The femtosecond laser pulse with uniform energy distribution can be a flat-top beam, i.e., a rectangular (or square) spot with uniform energy distribution. Through the beam shaping module, the Gaussian-distributed femtosecond laser pulse is converted into a flat-top beam with uniform energy distribution, making the intensity distribution of the beam irradiating the DMD more uniform, thereby improving the uniformity of the beam irradiating the sample M surface after passing through the objective lens assembly 40.

[0046] In one example, reference Figure 6 The beam shaping module 50 can be an aspherical mirror homogenizer 51, which may include one or more pairs of matched aspherical lenses. By mapping each point of the incident laser pulse onto each point of the output surface, it "disperses" and redistributes the Gaussian-distributed pulsed laser light, forming uniform illumination. Since beam shaping is based on the principle of refraction, the transmittance of the incident laser pulse is extremely high, typically reaching 95%, which helps reduce energy loss. Furthermore, the beam spot is relatively uniform, and the structure is relatively simple and compact, which is beneficial for further miniaturization. Of course, the beam shaping module 50 can be a diffractive optical element, a spatial light modulator, etc., as long as a uniform energy distribution beam spot can be obtained; no specific limitation is made here.

[0047] For example, the aspherical homogenizer 51 may include a first aspherical mirror and a second aspherical mirror. The first aspherical mirror is used to split and deflect the incident Gaussian beam (circularly polarized femtosecond laser pulse). The second aspherical mirror is used to collimate the split and deflected femtosecond laser pulse, so that the diverging light after passing through the first aspherical mirror is recollided, and these split tiny light spots are made to completely overlap on the focal plane, so that the concentrated energy at the center of the femtosecond laser pulse is redistributed to the edges, thereby achieving spot homogenization.

[0048] refer to Figure 3The optical system also includes a spatial filter-beam expander 60, which filters stray light from the circularly polarized femtosecond laser pulse S1 and expands the diameter of the filtered femtosecond laser pulse to obtain a femtosecond laser pulse with a larger spot size and less stray light. Beam expansion is used to match the larger spot size with the size of the DMD. For example, the spot diameter of the femtosecond laser output from the laser is typically 3 mm, while the size of an existing DMD is generally 9 mm. The spatial filter-beam expander makes the spot diameter of the femtosecond laser pulse 9 mm. Thus, after passing through the spatial filter-beam expander, a circularly polarized femtosecond laser pulse S2 with less stray light and a spot diameter expanded to 9 mm is obtained. Then, the circularly polarized femtosecond laser pulse S2 passes through the beam shaping module 50, resulting in a more uniform energy distribution. It then passes through the micromirror array 30 to obtain different patterns and is reflected to the objective lens assembly 40, thereby illuminating the surface of the sample M. Spatial filtering-beam expanding components can include spatial filtering components and beam expanding components. For example, spatial filtering components can include bandpass filters, pinhole filters, etc., and beam expanding components can be Galilean beam expanders, Keplerian beam expanders, etc., without specific limitations. Of course, the beam expanding factor can also be flexibly adjusted according to the size of the DMD, for example, 3 to 8 times, or it can also be used for beam contraction, without specific limitations.

[0049] In one example, reference Figure 4 and Figure 6 The spatial filtering-beam expander assembly 60 may sequentially include a first lens 61, a pinhole filter 62, and a second lens 63. The rear focal plane of the first lens 61 and the front focal plane of the second lens 63 coincide. The pinhole filter 62 is located at the rear focal plane of the first lens 61, and the focal length of the second lens 63 is greater than that of the first lens 61. The cooperation of the first and second lenses forms a beam expander system, and the integrated pinhole filter can also filter out stray light. In this way, not only is the structure simple and the cost low, but it can also achieve the functions of spatial filtering and beam expansion simultaneously.

[0050] refer to Figure 6 The optical system 100 may also include an image sensor 70, which is coaxially arranged with the objective lens assembly 40 and used to observe the pattern on the surface of the sample M. For example, the image sensor 70 can be a camera, a CCD sensor, etc.

[0051] Continue to refer to Figure 6 The optical system 100 may also include a dichroic mirror 71, so that light (such as reflected light) on the surface of the sample M can be transmitted through the dichroic mirror 71 and received by the image sensor 70, and the reflected light after passing through the digital micromirror device (DMD) is reflected by the dichroic mirror 71 and then passed through the objective lens assembly 40 to illuminate the surface of the sample M for laser direct writing.

[0052] In one example, reference Figure 6 The optical system 100 provided in this application may sequentially include a femtosecond laser 11, an electro-optic modulator 21, a spatial filtering-beam expander assembly 60 (sequentially including a first lens 61, a pinhole filter 62, and a second lens 63), a first reflecting mirror 64, an aspherical mirror homogenizer 51, a second reflecting mirror 65, a digital micromirror device (DMD) 31, a third reflecting mirror 66, a dichroic mirror 71, and an objective lens assembly 40 (sequentially including a tube mirror 41 and an objective lens 42).

[0053] The femtosecond laser 11 outputs linearly polarized femtosecond laser pulses S0. These pulses are then modulated into circularly polarized femtosecond laser pulses S1 by an electro-optic modulator 21. The electro-optic modulator 21 is controlled by a field-programmable gate array (FPGA), with a response time ≤50ns and an extinction ratio ≥30dB. The polarization state of the laser pulses is dynamically adjusted via the electro-optic modulator 21 to match the incident angle of the DMD.

[0054] In the spatial filtering-beam expander assembly 60, the rear focal plane of the first lens 61 and the front focal plane of the second lens 63 coincide. The pinhole filter 62 is located at the rear focal plane of the first lens 61, and the focal length of the second lens 63 is greater than that of the first lens 61. This allows the femtosecond laser pulse S1, modulated into a circularly polarized state, to have less stray light and a larger spot diameter (e.g., three times the spot diameter of the femtosecond laser pulse S0) to match the size of the DMD. The circularly polarized femtosecond laser pulse S2, with less stray light and a larger spot diameter, changes its transmission direction after passing through the first reflecting mirror 64, which is beneficial for achieving compactness and miniaturization of the optical system 100. Subsequently, the circularly polarized femtosecond laser pulse S2, with less stray light and a larger spot diameter, passes through the aspherical mirror homogenizer 51, where the energy of its spot is redistributed to obtain a rectangular (or square) spot with uniform energy distribution. A circularly polarized femtosecond laser pulse S3 with uniform energy distribution passes through the second reflector 65 again and illuminates the surface of the DMD 31. Based on a preset pattern, the operating state of each reflector in the DMD is controlled (on or off, i.e., by controlling the rotation angle to ±12° and the refresh rate to ≥20kHz) to generate a mask pattern. Afterward, it passes through the third reflector 66 and illuminates the dichroic mirror 71. The laser pulse reflected by the dichroic mirror 71 passes through the tube lens 41 and the objective lens 42 and illuminates the surface of the sample M for direct laser writing. It can be understood that after the laser pulse passes through the tube lens 41 and the objective lens 42, the size of its spot diameter can be reduced to 1 / 3 or less of its original size.

[0055] refer to Figures 1 to 7An embodiment of this application also provides an optical processing apparatus 200, including the optical system 100 and controller 80 described above. The optical processing apparatus 200 can be a femtosecond laser exposure machine.

[0056] Based on the control commands, the controller 80 can be used to control the light source module 10 to output linearly polarized femtosecond laser pulses S0 and adjust the linearly polarized femtosecond laser pulses S0 to circularly polarized femtosecond laser pulses S1, so that the circularly polarized femtosecond laser pulses S1 pass through the micromirror array 30 to generate different patterns and be focused onto the surface of the sample M.

[0057] Specifically, the controller 80 can be used to control parameters such as the repetition rate, pulse width, and output power (single pulse energy) of the femtosecond laser 11. The controller 80 can also be used to control the image sensor 70, and observe the pattern on the surface of the sample M by adjusting parameters such as the focal length, position, and resolution of the image sensor 70.

[0058] refer to Figure 6 and Figure 7 The optical processing equipment 200 may also include a displacement stage 90 (such as a triaxial displacement stage), on which the sample M is placed so that the pattern is focused onto the surface of the sample. By adjusting the height and specific position of the displacement stage 90, the movement of the sample is controlled so that the sample is located at the focal position of the objective lens, thereby performing femtosecond laser processing.

[0059] It's important to note that femtosecond laser exposure machines combine the ultrafast characteristics of femtosecond lasers with the maskless flexibility of direct-write technology. Specifically, femtosecond laser exposure machines utilize ultrafast, ultra-intense femtosecond laser pulses and a precisely controlled optical system to directly induce "nonlinear optical effects" on a sample M (such as photoresist or other photosensitive materials), thereby achieving nanoscale precision three-dimensional structure processing without the need for traditional physical masks. The induced "nonlinear optical effect" is primarily a two-photon absorption effect. Specifically, it utilizes the extremely high peak power of the femtosecond laser to cause the material to undergo a chemical reaction by simultaneously absorbing two low-energy photons, and this reaction is strictly confined to the laser focal point. It is precisely this two-photon absorption effect that enables femtosecond laser exposure machines to achieve maskless, true three-dimensional, high-resolution micro-nano fabrication technology.

[0060] It is understood that in this application, directional descriptions such as "upper," "lower," "inner," and "outer" are relative rather than absolute. These directional terms may be applicable when the optical processing equipment provided in this application is placed in the posture and position shown in the accompanying drawings.

[0061] It should be understood that although terms such as "first" or "second" may be used in this application to describe various elements (such as the first reflector and the second reflector), these elements are not defined by these terms, which are only used to distinguish one element from another.

[0062] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0063] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

[0064] The components and devices described in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the accompanying drawings. As those skilled in the art will recognize, these components and devices can be connected, arranged, and configured in any manner.

[0065] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical system, characterized in that, include: The light source module is used to output femtosecond laser pulses; A polarization modulation module is used to receive and modulate the polarization state of the femtosecond laser pulse into a circular polarization state; A micromirror array is used to receive and spatially modulate the circularly polarized femtosecond laser pulses to generate different patterns; Objective lens assembly for receiving and focusing the pattern onto the surface of the sample.

2. The optical system according to claim 1, further comprising a beam shaping module, the beam shaping module being used to receive and redistribute the energy of the circularly polarized femtosecond laser pulse to obtain a femtosecond laser pulse with uniform energy distribution, and the femtosecond laser pulse with uniform energy distribution irradiating the surface of the sample after passing through the micromirror array and the objective lens assembly.

3. The optical system according to claim 2, further comprising a spatial filtering-beam expander, the spatial filtering-beam expander being used to filter stray light from the circularly polarized femtosecond laser pulse and expand the diameter of the filtered femtosecond laser pulse so that the expanded femtosecond laser pulse, after passing through the beam shaping module, the micromirror array and the objective lens assembly, illuminates the surface of the sample.

4. The optical system according to claim 3, wherein the spatial filtering-beam expander assembly comprises, in sequence, a first lens, a pinhole filter, and a second lens, wherein the rear focal plane of the first lens and the front focal plane of the second lens coincide, the pinhole filter is located at the rear focal plane of the first lens, and the focal length of the second lens is greater than the focal length of the first lens.

5. The optical system according to claim 1, wherein the polarization modulation module includes an electro-optic modulator.

6. The optical system according to claim 1, wherein the objective lens assembly comprises a tube and an objective lens, and the front focal plane of the tube and the rear focal plane of the objective lens are optically conjugate.

7. The optical system according to claim 1, further comprising an image sensor, the image sensor being coaxially arranged with the objective lens assembly for observing patterns on the sample surface.

8. The optical system according to claim 5, further comprising a first lens, a pinhole filter, a second lens, an aspherical mirror homogenizer, a tube mirror, and an objective lens; The rear focal plane of the first lens and the front focal plane of the second lens coincide in position. The pinhole filter is located at the position of the rear focal plane of the first lens, and the focal length of the second lens is greater than the focal length of the first lens. The front focal plane of the tube lens and the rear focal plane of the objective lens are optically conjugate. The femtosecond laser pulse passes sequentially through the electro-optic modulator, the first lens, the pinhole filter, the second lens, the aspherical mirror homogenizer, the micromirror array, the tube mirror, and the objective lens before being focused onto the surface of the sample.

9. An optical processing device, characterized in that, Including the optical system and controller as described in any one of claims 1 to 8, Based on control commands, the controller controls the light source module to output femtosecond laser pulses and adjusts the polarization state of the femtosecond laser pulses to a circularly polarized state. This allows the circularly polarized femtosecond laser pulses to pass through a micromirror array, generating different patterns that are then focused onto the sample surface. The controller is also used to control the image sensor to observe the pattern on the sample surface.

10. The optical processing apparatus according to claim 9, further comprising a displacement stage, wherein the sample is disposed on the displacement stage to focus the pattern onto the surface of the sample; The controller is also used to control the displacement stage to move the sample.

Images