A method and apparatus for modulating randomly polarized light using a liquid crystal spatial light modulator.

Abstract

This invention discloses a method and apparatus for modulating randomly polarized light using a liquid crystal spatial light modulator, relating to the field of optical field manipulation technology. The apparatus includes core components such as a laser, a two-in-one optical fiber, a beam expander, a polarizing beam splitter (PBS), a half-wave plate, an optical fiber coupler, a polarization-maintaining fiber, and a liquid crystal spatial light modulator, which can be either reflective or transmissive. The method uses the PBS to split randomly polarized light into parallel and perpendicular polarized components. The perpendicularly polarized light is converted by a 45° half-wave plate and then transmitted through the polarization-maintaining fiber, merging with the original parallel polarized component, or directly used for preheating the sample to be processed. The merged single-beam parallel polarized light is then modulated by the liquid crystal spatial light modulator. This invention achieves single-beam modulation, is suitable for high-power, large-spot applications, reduces the difficulty of hologram fabrication, simplifies the optical path structure, reduces light energy loss, and is applicable to scenarios such as 3D metal printing and laser welding.

Description

Technical Field

[0001] This invention relates to the field of light field modulation technology, specifically to a method and apparatus for modulating randomly polarized light using a liquid crystal spatial light modulator. Background Technology

[0002] like Figure 4 As shown, prior art discloses a beam shaping device and method based on waveplate polarization conversion, with application number CN120595486A. This invention relates to the field of laser processing technology. The device uses a first polarizing beam splitter (PBS) to split randomly polarized light into S / P light. A first half-waveplate converts the S light into P light. After modulation by a conventional liquid crystal on silicon spatial light modulator (LCoS SLM), the P light is converted back into S light by a second half-waveplate, and then the beam is combined by a second PBS. The method includes steps such as beam splitting, polarization conversion, phase modulation, beam combining, and beam expansion and focusing. This invention utilizes a combination of double half-waveplates and a conventional PBS to achieve a laser energy utilization rate exceeding 85%, is compatible with commercial SLM equipment, and significantly improves the processing efficiency of the shaped ring beam compared to a high-sigma beam. It is suitable for laser welding and metal 3D printing, solving the problems of energy waste and high cost.

[0003] However, in the aforementioned document, the silicon-based liquid crystal spatial light modulator in the device needs to simultaneously irradiate two laser beams onto different zones. But in certain industrial scenarios, such as 500W high-power 3D printing applications, to ensure the spatial light modulator can safely withstand such high power, the laser beam is typically expanded to a larger spot size, such as 8mm (1 / e) using the beam expander shown in the diagram above. 2 The beam diameter is relatively small, while commercial liquid crystal spatial light modulators are small (within 15mm), making it difficult to have space to simultaneously and independently illuminate two laser beams. Furthermore, it is difficult to modulate two beams on a single spatial light modulator at the same time, making the generation of the modulation hologram more challenging. In addition, this modulation method uses multiple PBS, 1 / 2 glass slides, and total reflection surfaces, making the optical path assembly and adjustment more difficult.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for modulating randomly polarized light using a liquid crystal spatial light modulator, in order to solve the problems mentioned in the background art: 1. The spatial light modulator modulates two beams of light simultaneously and independently, and the size of the spatial light modulator cannot meet the requirements of high-power and large-spot applications; 2. The spatial light modulator modulates two beams of light simultaneously and independently, and the holographic algorithm is difficult to fabricate; 3. The optical path needs to be equipped with multiple PBS, 1 / 2 glass slides, and total reflection mirrors, which makes the optical path assembly and adjustment difficult.

[0006] To solve the above-mentioned technical problems, the present invention provides a liquid crystal spatial light modulator device for modulating random polarized light, comprising a laser, a two-in-one fiber, a beam expander, a polarizing beam splitter (PBS), a half-wave plate, a fiber coupler, a polarization-maintaining fiber, a liquid crystal spatial light modulator, a 4f optical module, a processing lens, and a reflector. Laser: Used to output randomly polarized light; Two-in-one fiber: It has branch one and branch two. Branch one is used to transmit randomly polarized light output from the laser to the beam expander, and branch two is a polarization-maintaining fiber used to transmit parallel polarized light after polarization conversion. Beam expander: Used to expand the randomly polarized light transmitted in a dual-fiber tributary, and also to expand the parallel polarized light output from a polarization-maintaining fiber. Polarizing beam splitter (PBS): Used to split randomly polarized light after beam expansion into parallel polarized light components and vertical polarized light components. The parallel polarized light components are directly transmitted, while the vertical polarized light components are reflected. At the same time, it allows the polarization-maintaining fiber to pass through the parallel polarized light after beam expansion and merge with the directly transmitted parallel polarized light components. 1 / 2 wave plate: Set at an angle of 45°, corresponding to the reflecting side of the polarizing beam splitter (PBS), used to convert vertically polarized light reflected by the PBS into parallel polarized light; Fiber optic coupler: Located on the output side of the half-wave plate, used to couple the parallel polarized light converted by the half-wave plate to the polarization-maintaining fiber; Polarization-maintaining fiber: As the second branch of a two-in-one fiber, it is used to transmit parallel polarized light coupled by a fiber coupler. Liquid crystal spatial light modulator: Its alignment direction is consistent with the polarization direction of the incident parallel polarized light, and it is used to receive and modulate the combined parallel polarized light. The liquid crystal spatial light modulator is either reflective or transmissive. 4f optical module: Set on the light-emitting side of the liquid crystal spatial light modulator, used to shape the modulated beam; Processing lens: Connected to the light-emitting side of the 4f optical module, used to focus the shaped light beam onto the surface of the sample to be processed; The reflector, positioned on the reflecting side of the polarizing beam splitter (PBS), reflects the vertically polarized light reflected by the PBS onto the surface of the sample to be processed. This device integrates a single fiber, a 45° half-wave plate, and fiber couplers to create a simple and efficient optical path structure. The core functions of beam splitting and combining are achieved with only a single polarizing beam splitter (PBS), avoiding the complex configuration of multiple PBSs, half-wave plates, and total reflection surfaces found in existing technologies, significantly reducing the difficulty of optical path assembly and adjustment. Simultaneously, the device converts the two beams that originally required independent modulation into a single-beam modulation mode, allowing the beam to expand to the physical size of a liquid crystal spatial light modulator. This effectively adapts to high-power, large-spot applications, solving the problem that commercially available small-size liquid crystal spatial light modulators cannot meet high-power requirements. Furthermore, the single-beam modulation mode significantly reduces the difficulty of hologram fabrication, improving the practicality and reliability of the device.

[0007] A method for using a liquid crystal spatial light modulator to modulate randomly polarized light includes the following steps: Step 1: The laser outputs randomly polarized light, which is transmitted to the beam expander through the first branch of the two-in-one fiber optic cable. The beam expander then expands the randomly polarized light. Step 2: The expanded random polarized light is incident on the polarizing beam splitter (PBS). The polarizing beam splitter (PBS) separates the random polarized light into a parallel polarized light component and a perpendicular polarized light component. The parallel polarized light component passes directly through the polarizing beam splitter (PBS), while the perpendicular polarized light component is reflected by the polarizing beam splitter (PBS). Step 3: The vertically polarized light reflected by the polarizing beam splitter (PBS) is reflected by a mirror onto the surface of the sample to be processed, thus preheating the sample. Step 4: Parallel polarized light passing through the polarizing beam splitter (PBS) is incident on the reflective liquid crystal spatial light modulator. The polarization direction of the parallel polarized light is consistent with the alignment direction of the reflective liquid crystal spatial light modulator. The reflective liquid crystal spatial light modulator modulates the parallel polarized light and then reflects it out. Step 5: The beam modulated by the reflective liquid crystal spatial light modulator is incident on the 4f optical module, and the 4f optical module performs beam shaping. Step Six: The shaped laser beam is focused by the processing lens and applied to the preheated sample to be processed, completing the laser beam shaping process; this method corresponds to... Figure 1The proposed technical solution utilizes the reflected vertically polarized light for preheating the sample to be processed, fully leveraging potentially wasted light energy and significantly improving laser energy utilization. This avoids energy waste and the additional work and risks associated with processing idle light. Simultaneously, a reflective liquid crystal spatial light modulator is used to modulate a single beam of parallel polarized light, eliminating the need to process two beams separately on a single modulator. This reduces the complexity of the holographic algorithm and results in a simple optical path structure that is easy to assemble and adjust. In applications such as 3D metal printing or welding, the combination of preheating and modulated beam processing can further improve processing quality and efficiency, expanding the application scenarios of the device.

[0008] A method for using a liquid crystal spatial light modulator to modulate randomly polarized light includes the following steps: Step 1: The laser outputs randomly polarized light, which is transmitted to the beam expander through the first branch of the two-in-one fiber optic cable. The beam expander then expands the randomly polarized light. Step 2: The expanded random polarized light is incident on the polarizing beam splitter (PBS). The polarizing beam splitter (PBS) separates the random polarized light into a parallel polarized light component and a perpendicular polarized light component. The parallel polarized light component passes directly through the polarizing beam splitter (PBS), while the perpendicular polarized light component is reflected by the polarizing beam splitter (PBS). Step 3: The vertically polarized light reflected by the polarizing beam splitter (PBS) is incident on a half-wave plate set at 45°, and is converted into parallel polarized light by the half-wave plate; Step 4: The parallel polarized light converted by the 1 / 2 waveplate is coupled to the second branch (polarization-maintaining fiber) of the two-in-one fiber through an optical fiber coupler, and the parallel polarized light is transmitted by the polarization-maintaining fiber. Step 5: The parallel polarized light output from the polarization-maintaining fiber re-enters the beam expander for beam expansion. The expanded parallel polarized light passes through the polarization beam splitter (PBS) and merges with the parallel polarized light component that passed directly through the polarization beam splitter (PBS) in Step 2. Step Six: The combined parallel polarized light is incident on a reflective liquid crystal spatial light modulator. The polarization direction of the parallel polarized light is consistent with the alignment direction of the reflective liquid crystal spatial light modulator. The reflective liquid crystal spatial light modulator modulates the parallel polarized light and then reflects it out to obtain modulated light. This method corresponds to... Figure 2The proposed technical solution, through the combination of a half-wave plate, fiber coupler, and polarization-maintaining fiber, converts vertically polarized light, which cannot be directly modulated, into parallel polarized light and merges it with the original parallel polarized light component. This achieves full recovery and utilization of optical energy and reduces optical loss. The reflective liquid crystal spatial light modulator only needs to modulate the parallel polarized light after merging a single beam, eliminating the need for partitioning the two beams. This not only adapts to the use of commercially available small-sized liquid crystal spatial light modulators but also expands the beam to the physical size of the modulator, meeting the requirements of high-power, large-spot applications. Simultaneously, the single-beam modulation mode reduces the difficulty of hologram fabrication, simplifies the optical path structure, and facilitates assembly and adjustment, effectively overcoming the shortcomings of complex optical paths and high modulation difficulty in existing technologies.

[0009] A method for using a liquid crystal spatial light modulator to modulate randomly polarized light includes the following steps: Step 1: The laser outputs randomly polarized light, which is transmitted to the beam expander through the first branch of the two-in-one fiber optic cable. The beam expander then expands the randomly polarized light. Step 2: The expanded random polarized light is incident on the polarizing beam splitter (PBS). The polarizing beam splitter (PBS) separates the random polarized light into a parallel polarized light component and a perpendicular polarized light component. The parallel polarized light component passes directly through the polarizing beam splitter (PBS), while the perpendicular polarized light component is reflected by the polarizing beam splitter (PBS). Step 3: The vertically polarized light reflected by the polarizing beam splitter (PBS) is incident on a half-wave plate set at 45°, and is converted into parallel polarized light by the half-wave plate; Step 4: The parallel polarized light converted by the 1 / 2 waveplate is coupled to the second branch (polarization-maintaining fiber) of the two-in-one fiber through an optical fiber coupler, and the parallel polarized light is transmitted by the polarization-maintaining fiber. Step 5: The parallel polarized light output from the polarization-maintaining fiber re-enters the beam expander for beam expansion. The expanded parallel polarized light passes through the polarization beam splitter (PBS) and merges with the parallel polarized light component that passed directly through the polarization beam splitter (PBS) in Step 2. Step Six: The combined parallel polarized light is incident on a transmissive liquid crystal spatial light modulator. The polarization direction of the parallel polarized light is consistent with the alignment direction of the transmissive liquid crystal spatial light modulator. The transmissive liquid crystal spatial light modulator modulates the parallel polarized light and then transmits it out to obtain modulated light. This method corresponds to... Figure 3The proposed technical solution employs a transmissive liquid crystal spatial light modulator to achieve single-beam modulation, complementing the reflective approach and providing flexible options for various application scenarios. Through polarization conversion and beam merging techniques, all polarization components of randomly polarized light are fully utilized, reducing light energy waste and improving energy efficiency. Similarly, the single-beam modulation mode reduces the complexity of holographic algorithms, and the optical path does not require a complex total internal reflection structure, simplifying assembly and adjustment. The application of the transmissive liquid crystal spatial light modulator can also adapt to scenarios with special requirements for the optical path transmission direction, further broadening the device's applicability. It also meets the modulator size requirements of high-power, large-spot applications, combining practicality and flexibility.

[0010] Compared with the prior art, the beneficial effects of the present invention are: By utilizing waveplates, fiber couplers, and polarization-maintaining fibers, light that could not be modulated by a liquid crystal spatial light modulator can be reused, reducing light loss and avoiding the need for processing that portion of the light and the associated risks. Furthermore, this device has a simple structure; only a single beam needs to be modulated on the liquid crystal spatial light modulator, allowing the beam to be expanded to the physical size of the modulator, increasing the laser power that the liquid crystal spatial light can withstand. Moreover, single-beam modulation makes holographic fabrication easier. Attached Figure Description

[0011] Figure 1 In a method and apparatus for modulating randomly polarized light with a liquid crystal spatial light modulator, Example 1 shows the optical path principle for using vertically polarized light to illuminate a sample. Figure 2 In a method and apparatus for modulating randomly polarized light using a liquid crystal spatial light modulator, Example 2 shows the optical path diagram of a reflective liquid crystal spatial light modulator for modulating randomly polarized light. Figure 3 In a method and apparatus for modulating randomly polarized light with a liquid crystal spatial light modulator, the optical path diagram of the transmissive liquid crystal spatial light modulator for modulating randomly polarized light is shown in Embodiment 3. Figure 4 This is a structural diagram of existing publicly available documents. Detailed Implementation

[0012] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] Please see Figures 1 to 4This invention provides a technical solution: a method and apparatus for modulating randomly polarized light using a liquid crystal spatial light modulator. This allows for the cutting of long focal depths and multi-focal chamfers on a single machine, reducing the number of processes and lowering internal equipment costs. Combined with the spatial light modulator's ability to generate multiple beams in special arrangements, parallel processing significantly reduces processing time and improves efficiency. Furthermore, due to the reconfigurable dynamic characteristics of the spatial light modulator, different holograms can be flexibly generated for glass samples of varying thicknesses, meeting the processing requirements of glass samples of different thicknesses on the same machine.

[0014] Example 1, corresponding Figure 1 Vertically polarized light preheating + reflective modulation processing: I. Device Composition and Connections: The liquid crystal spatial light modulator modulating random polarized light device in this embodiment includes a laser, a two-in-one optical fiber, a beam expander, a polarizing beam splitter (PBS), a reflective liquid crystal spatial light modulator, a 4f optical module, a processing lens, and a reflector; the connections and positional relationships of each component are as follows: The output end of the laser is fixedly connected to the input end of branch one of the two-in-one optical fiber, which is used to guide the randomly polarized light output by the laser into the two-in-one optical fiber. The output end of branch 1 of the two-in-one fiber is aligned with the incident port of the beam expander to ensure that the randomly polarized light transmitted by branch 1 can be completely incident on the beam expander. The beam expander is positioned opposite to the incident side of the polarizing beam splitter (PBS), and the expanded random polarized light is incident on the beam splitting surface of the PBS in a straight line. The reflector is positioned on the reflecting side of the polarizing beam splitter (PBS). The mirror angle of the reflector is calibrated to ensure that the vertically polarized light reflected by the PBS can be accurately reflected to the preset preheating area of ​​the sample to be processed. The reflective liquid crystal spatial light modulator is set on the transmission side of the polarizing beam splitter (PBS), and its alignment direction is consistent with the polarization direction of the parallel polarized light transmitted by the PBS. The effective working surface of the reflective liquid crystal spatial light modulator is adapted to the incident parallel polarized light. The incident side of the 4f optical module is positioned opposite to the reflective side of the reflective liquid crystal spatial light modulator, and is used to receive the light beam reflected after being modulated by the reflective liquid crystal spatial light modulator; The incident end of the processing lens is fixedly connected to the light-emitting side of the 4f optical module, and the light-emitting end of the processing lens is set to correspond to the processing area of ​​the sample to be processed, so as to ensure that the beam after being shaped by the 4f optical module can be focused on the preheated processing area.

[0015] II. Working Principle and Procedures: The method of using the device in this embodiment specifically includes the following steps: Step 1: Start the laser. The laser outputs randomly polarized light, which is stably transmitted to the beam expander via branch one of the two-in-one fiber. The beam expander expands the randomly polarized light according to preset parameters, increasing the beam diameter to a size suitable for subsequent PBS beam splitting and reflective liquid crystal spatial light modulator operation (e.g., 8mm, 1 / e). 2 ); Step 2: The expanded random polarized light is incident on the polarizing beam splitter (PBS) along the optical path. The beam splitting surface of the PBS separates the random polarized light into a parallel polarized light component and a vertical polarized light component. The parallel polarized light component is directly transmitted through the PBS to the reflective liquid crystal spatial light modulator, while the vertical polarized light component is reflected by the beam splitting surface of the PBS to the reflector. Step 3: The mirror reflects the received vertically polarized light onto the surface of the sample to be processed. The energy carried by the vertically polarized light preheats the sample in this area. The preheating temperature is preset according to the characteristics of the processing material (such as metal or glass) to ensure that the sample surface can quickly respond to the modulated beam during subsequent processing. Step 4: Parallel polarized light passing through the PBS is continuously incident on the reflective liquid crystal spatial light modulator. Since the polarization direction of the parallel polarized light is consistent with the alignment direction of the reflective liquid crystal spatial light modulator, the modulation principle is started normally. The reflective liquid crystal spatial light modulator performs phase modulation on the parallel polarized light according to the preset hologram. After the modulation is completed, the beam is reflected and output. Step 5: The beam modulated by the reflective liquid crystal spatial light modulator is incident on the 4f optical module. The 4f optical module performs beam expansion or contraction shaping on the beam to make the beam size, divergence angle and other parameters adapt to the working requirements of the lens. Step Six: The shaped beam is focused by the processing lens to form a spot that meets the processing requirements. This spot acts on the processing area of ​​the preheated sample to be processed, completing the laser beam shaping process, such as 3D metal printing and laser welding.

[0016] This embodiment utilizes vertically polarized light for sample preheating, fully recovering and reusing potentially idle light energy from traditional technologies. This significantly improves energy utilization compared to existing technologies, avoiding energy waste and the additional equipment investment and safety risks associated with processing idle light. Furthermore, the reflective liquid crystal spatial light modulator only needs to modulate a single beam of parallel polarized light, eliminating the need for partitioning two beams. This solves the problem of commercially available small-size modulators being unsuitable for high-power, large-spot applications and reduces the algorithmic complexity of hologram fabrication. In addition, the optical path requires only a single PBS and a reflector, resulting in a simple structure and simplified assembly process, significantly reducing the difficulty and time cost of optical path debugging.

[0017] Example 2: Corresponding Figure 2 Reflective liquid crystal spatial light modulator single-beam convergence modulation: I. Device Composition and Connections: The liquid crystal spatial light modulator for modulating randomly polarized light in this embodiment includes a laser, a two-in-one fiber, a beam expander, a polarizing beam splitter (PBS), a half-wave plate, a fiber coupler, a polarization-maintaining fiber, and a reflective liquid crystal spatial light modulator. The connections and positional relationships of each component are as follows: The output end of the laser is fixedly connected to the input end of branch one of the two-in-one fiber, and the output end of branch one of the two-in-one fiber is aligned with the incident port of the beam expander. The beam expander's output side is positioned opposite to the polarizing beam splitter (PBS)'s incident side to ensure that the expanded, randomly polarized light can be completely incident on the PBS; The half-wave plate is set on the reflecting side of the polarizing beam splitter (PBS). The half-wave plate is set at an angle of 45°, and its incident surface is perpendicular to the transmission direction of the vertically polarized light reflected by the PBS, ensuring that the vertically polarized light can pass through the half-wave plate completely. The incident side of the fiber optic coupler is set opposite to the output side of the 1 / 2 wave plate. The output end of the fiber optic coupler is fixedly connected to one end of the polarization-maintaining fiber, which is the second branch of the two-in-one fiber. The other end of the polarization-maintaining fiber is connected to the incident port of the beam expander. The beam expander has dual incident channels, which are adapted to the first and second branches of the two-in-one fiber respectively. The reflective liquid crystal spatial light modulator is set on the transmission side of the polarizing beam splitter (PBS), and its alignment direction is consistent with the polarization direction of the parallel polarized light after transmission and merging through the PBS. The effective working surface of the reflective liquid crystal spatial light modulator is perpendicular to the incident light.

[0018] II. Working Principle and Procedures: The method of using the device in this embodiment specifically includes the following steps: Step 1: Start the laser. The laser outputs randomly polarized light, which is transmitted to the beam expander via branch 1 of the two-in-one fiber. The beam expander expands the randomly polarized light to make the beam size match the beam splitting requirements of the PBS. Step 2: The expanded random polarized light is incident on the polarizing beam splitter (PBS). The PBS separates the random polarized light into a parallel polarized light component and a vertical polarized light component. The parallel polarized light component is directly transmitted through the PBS to the reflective liquid crystal spatial light modulator, while the vertical polarized light component is reflected by the PBS to the half-wave plate. Step 3: The vertically polarized light reflected by the PBS is incident on a half-wave plate set at 45°. The half-wave plate changes the polarization direction of the vertically polarized light, converting it into parallel polarized light. Step 4: The parallel polarized light after being converted by the 1 / 2 waveplate is incident on the fiber coupler. The fiber coupler efficiently couples the parallel polarized light to the second branch (polarization-maintaining fiber) of the two-in-one fiber. The polarization-maintaining fiber keeps the polarization direction of the parallel polarized light from shifting during transmission. Step 5: The parallel polarized light output from the polarization-maintaining fiber enters another incident channel of the beam expander. The beam expander expands the parallel polarized light again to ensure that its beam size is consistent with the parallel polarized light component that directly passes through the PBS in Step 2. The expanded parallel polarized light passes through the polarization beam splitter (PBS) and merges with the parallel polarized light component that directly passes through the PBS in Step 2 to form a parallel polarized light with higher intensity and uniform polarization direction. Step 6: The combined parallel polarized light is incident on the reflective liquid crystal spatial light modulator. Since the polarization direction of the parallel polarized light is consistent with the alignment direction of the reflective liquid crystal spatial light modulator, the reflective liquid crystal spatial light modulator performs phase modulation on the parallel polarized light. After modulation, the beam is reflected and output to obtain the modulated light that meets the requirements.

[0019] This embodiment utilizes the synergistic effect of a half-wave plate, fiber coupler, and polarization-maintaining fiber to convert vertically polarized light, which cannot be directly modulated, into parallel polarized light and merge it with the original parallel polarized light component. This maximizes the utilization of optical energy and reduces optical loss. The reflective liquid crystal spatial light modulator only needs to modulate the parallel polarized light after the single beam is merged, eliminating the need to divide the modulator into independent regions to process two beams. This not only adapts to the physical size limitations of commercial small-size liquid crystal spatial light modulators but also expands the beam to the maximum effective size of the modulator, meeting the needs of high-power, large-spot applications such as 500W. At the same time, the single-beam modulation mode significantly reduces the algorithmic complexity of hologram production. The optical path only requires a single PBS and a core polarization conversion component, resulting in a simple structure and low assembly and adjustment difficulty. This solves the core defects of complex optical paths and high modulation difficulty in existing technologies.

[0020] Example 3: Corresponding Figure 3 Transmissive liquid crystal spatial light modulator single-beam convergence modulation: I. Device Composition and Connections: The liquid crystal spatial light modulator modulating randomly polarized light device in this embodiment includes a laser, a two-in-one fiber, a beam expander, a polarizing beam splitter (PBS), a half-wave plate, a fiber coupler, a polarization-maintaining fiber, and a transmissive liquid crystal spatial light modulator; the connections and positional relationships of each component are as follows: The output end of the laser is fixedly connected to the input end of branch one of the two-in-one fiber, and the output end of branch one of the two-in-one fiber is aligned with the incident port of the beam expander. The beam expander's output side is positioned opposite to the polarizing beam splitter (PBS)'s incident side to ensure that the expanded, randomly polarized light is completely incident on the PBS; The half-wave plate is positioned on the reflecting side of the polarizing beam splitter (PBS), with an angle of 45°. Its incident surface is perpendicular to the transmission direction of the vertically polarized light reflected by the PBS. The incident side of the fiber optic coupler is set opposite to the output side of the half-wave plate. The output end of the fiber optic coupler is fixedly connected to one end of the polarization-maintaining fiber, which is the second branch of the two-in-one fiber. The other end of the polarization-maintaining fiber is connected to the incident port of the beam expander (the beam expander has dual incident channels). The transmissive liquid crystal spatial light modulator is set on the transmission side of the polarizing beam splitter (PBS). Its alignment direction is consistent with the polarization direction of the parallel polarized light after transmission and merging through the PBS. The incident surface of the transmissive liquid crystal spatial light modulator is perpendicular to the incident light, and the light output side corresponds to subsequent light receiving or application equipment, such as beam detection equipment or processing execution equipment.

[0021] II. Working Principle and Procedures: The method of using the device in this embodiment specifically includes the following steps: Step 1: Start the laser. The laser outputs randomly polarized light, which is transmitted to the beam expander via branch 1 of the two-in-one fiber. The beam expander expands the randomly polarized light to meet the beam splitting requirements of the PBS. Step 2: The expanded random polarized light is incident on the polarizing beam splitter (PBS). The PBS separates the random polarized light into a parallel polarized light component and a vertical polarized light component. The parallel polarized light component is directly transmitted through the PBS to the transmissive liquid crystal spatial light modulator, while the vertical polarized light component is reflected by the PBS to the half-wave plate. Step 3: The vertically polarized light reflected by the PBS is incident on a half-wave plate set at 45°, and is converted into parallel polarized light by the half-wave plate; Step 4: The parallel polarized light after being converted by the 1 / 2 waveplate is coupled to the second branch (polarization-maintaining fiber) of the two-in-one fiber through an optical fiber coupler. The polarization-maintaining fiber stably transmits the parallel polarized light, ensuring that its polarization direction does not change. Step 5: The parallel polarized light output from the polarization-maintaining fiber re-enters the beam expander for beam expansion. The expanded parallel polarized light passes through the polarization beam splitter (PBS) and merges with the parallel polarized light component that directly passed through the PBS in Step 2, forming a beam of parallel polarized light with uniform polarization direction and stable intensity. Step 6: The combined parallel polarized light is incident on the transmissive liquid crystal spatial light modulator. Since the polarization direction of the parallel polarized light is consistent with the alignment direction of the transmissive liquid crystal spatial light modulator, the transmissive liquid crystal spatial light modulator performs phase modulation on the parallel polarized light according to the preset hologram. After modulation, the beam is transmitted and output to obtain modulated light that meets the application requirements.

[0022] This embodiment employs a transmissive liquid crystal spatial light modulator, complementing the reflective scheme and adapting to application scenarios with specific requirements for optical path transmission direction, such as equipment integration scenarios where the beam needs to be transmitted continuously along a straight line. Through polarization conversion and beam merging technology, all polarization components of randomly polarized light are fully utilized, significantly improving energy utilization. Similarly, the single-beam modulation mode solves the problems of poor modulator size adaptability and complex holographic algorithms in existing technologies, and the optical path structure is simple, requiring only a core polarization conversion component and a single PBS, making assembly and adjustment easy and enabling rapid equipment setup and debugging. Furthermore, the application of the transmissive liquid crystal spatial light modulator further broadens the applicability of this invention, adapting it to various optical field manipulation scenarios such as laser communication and beam shaping detection.

[0023] In summary, all three embodiments are based on the core technical concept of this invention: a single-beam modulation architecture combined with polarization conversion and energy recovery. They provide specific solutions for different application scenarios: Embodiment 1 focuses on processing scenarios such as 3D printing and welding, improving processing efficiency and quality through a preheating function; Embodiments 2 and 3 respectively utilize reflective and transmissive liquid crystal spatial light modulators to adapt to different optical path layout requirements. All three embodiments overcome the core shortcomings of existing technologies, such as poor modulator size adaptability, complex holographic algorithms, and difficulty in optical path assembly and adjustment. They possess significant advantages such as simple structure, high energy utilization, and strong practicality, and can comprehensively cover various application needs in the field of light field manipulation technology.

Claims

1. A device for modulating randomly polarized light by a liquid crystal spatial light modulator, characterized by: This includes lasers, two-in-one optical fibers, beam expanders, polarizing beam splitters (PBS), half-wave plates, fiber couplers, polarization-maintaining fibers, liquid crystal spatial light modulators, 4f optical modules, processing lenses, and reflectors. Laser: Used to output randomly polarized light; Two-in-one fiber: It has branch one and branch two. Branch one is used to transmit randomly polarized light output from the laser to the beam expander, and branch two is a polarization-maintaining fiber used to transmit parallel polarized light after polarization conversion. Beam expander: Used to expand the randomly polarized light transmitted in a dual-fiber tributary, and also to expand the parallel polarized light output from a polarization-maintaining fiber. Polarizing beam splitter: used to split randomly polarized light after beam expansion into parallel polarized light components and vertical polarized light components. The parallel polarized light components are directly transmitted, while the vertical polarized light components are reflected. At the same time, it allows the polarization-maintaining fiber to pass through the parallel polarized light after beam expansion and merge with the directly transmitted parallel polarized light components. 1 / 2 wave plate: Set at an angle of 45°, corresponding to the reflecting side of the polarizing beam splitter, used to convert the vertically polarized light reflected by the PBS into parallel polarized light; Fiber optic coupler: Located on the output side of the half-wave plate, used to couple the parallel polarized light converted by the half-wave plate to the polarization-maintaining fiber; Polarization-maintaining fiber: As the second branch of a two-in-one fiber, it is used to transmit parallel polarized light coupled by a fiber coupler. Liquid crystal spatial light modulator: Its alignment direction is consistent with the polarization direction of the incident parallel polarized light. It is used to receive and modulate the combined parallel polarized light. Liquid crystal spatial light modulator is one of the reflective and transmissive types. 4f optical module: Set on the light-emitting side of the liquid crystal spatial light modulator, used to shape the modulated beam; Processing lens: Connected to the light-emitting side of the 4f optical module, used to focus the shaped light beam onto the surface of the sample to be processed.

2. The method of using a liquid crystal spatial light modulator to modulate randomly polarized light according to claim 1, wherein: Includes the following steps: Step 1: The laser outputs randomly polarized light, which is transmitted to the beam expander through the first branch of the two-in-one fiber optic cable. The beam expander then expands the randomly polarized light. Step 2: The expanded random polarized light is incident on the polarizing beam splitter. The polarizing beam splitter separates the random polarized light into a parallel polarized light component and a perpendicular polarized light component. The parallel polarized light component passes directly through the polarizing beam splitter, while the perpendicular polarized light component is reflected by the polarizing beam splitter. Step 3: The vertically polarized light reflected by the polarizing beam splitter is incident on a half-wave plate set at 45°, and is converted into parallel polarized light by the half-wave plate; Step 4: The parallel polarized light after being converted by the 1 / 2 waveplate is coupled to the second branch of the two-in-one fiber, namely the polarization-maintaining fiber, through an optical fiber coupler, and the parallel polarized light is transmitted by the polarization-maintaining fiber. Step 5: The parallel polarized light output from the polarization-maintaining fiber re-enters the beam expander for beam expansion. The expanded parallel polarized light passes through the polarization beam splitter and merges with the parallel polarized light component that passed directly through the polarization beam splitter in Step 2. Step 6: The combined parallel polarized light is incident on the reflective liquid crystal spatial light modulator. The polarization direction of the parallel polarized light is consistent with the alignment direction of the reflective liquid crystal spatial light modulator. The reflective liquid crystal spatial light modulator modulates the parallel polarized light and then reflects it out to obtain the modulated light.

3. The method of using a liquid crystal spatial light modulator to modulate randomly polarized light as described in claim 1, characterized in that: Includes the following steps: Step 1: The laser outputs randomly polarized light, which is transmitted to the beam expander through the first branch of the two-in-one fiber optic cable. The beam expander then expands the randomly polarized light. Step 2: The expanded random polarized light is incident on the polarizing beam splitter. The polarizing beam splitter separates the random polarized light into a parallel polarized light component and a perpendicular polarized light component. The parallel polarized light component passes directly through the polarizing beam splitter, while the perpendicular polarized light component is reflected by the polarizing beam splitter. Step 3: The vertically polarized light reflected by the polarizing beam splitter is incident on a half-wave plate set at 45°, and is converted into parallel polarized light by the half-wave plate; Step 4: The parallel polarized light after being converted by the 1 / 2 waveplate is coupled to the second branch of the two-in-one fiber, namely the polarization-maintaining fiber, through an optical fiber coupler, and the parallel polarized light is transmitted by the polarization-maintaining fiber. Step 5: The parallel polarized light output from the polarization-maintaining fiber re-enters the beam expander for beam expansion. The expanded parallel polarized light passes through the polarization beam splitter and merges with the parallel polarized light component that passed directly through the polarization beam splitter in Step 2. Step 6: The combined parallel polarized light is incident on the transmissive liquid crystal spatial light modulator. The polarization direction of the parallel polarized light is consistent with the alignment direction of the transmissive liquid crystal spatial light modulator. The transmissive liquid crystal spatial light modulator modulates the parallel polarized light and then transmits it out to obtain the modulated light.

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