Liquid crystal phase array return light path fast response large angle light beam deflection system and method

Abstract

The application discloses a liquid crystal phased array backhaul optical path fast response large-angle light beam deflection system, which comprises a laser, a polarizer, a polarization beam splitter prism, a Faraday optical rotator, a first total reflection prism, a liquid crystal optical phased array, a second total reflection prism and a total reflection plane mirror; the outgoing light beam of the laser sequentially passes through the polarizer, the polarization beam splitter prism, the Faraday optical rotator and the liquid crystal optical phased array and then enters the second total reflection prism, is reflected multiple times between the second total reflection prism, the liquid crystal optical phased array and the first total reflection prism and is emitted from the last reflecting surface of the first total reflection prism, enters the total reflection plane mirror, is reflected by the total reflection plane mirror and then returns to the first total reflection prism, returns along the light path when entering, and is emitted through the polarization beam splitter prism. The application adopts sub-aperture partition control and split light optical rotator backhaul return light path design, and can realize large-angle, high deflection efficiency, fast response and low energy loss based on a single spatial light modulator.

Description

Technical Field

[0001] This invention belongs to the fields of light field modulation, optical phased array control, and free space optical communication technology. In particular, it relates to a fast-response large-angle beam deflection system for the backhaul optical path of a liquid crystal phased array, and a method for beam deflection using this system. Background Technology

[0002] With the in-depth development of space laser communication technology, my country will construct a space-bandwidth backbone communication network and an integrated air-space-ground three-dimensional network based on laser communication technology. As the main node of the space laser broadband network, the free-space laser communication system urgently needs lightweight, agile, and large-angle beam deflection capabilities. Traditional mechanical laser control systems are slow, have low pointing accuracy, are complex, and cannot achieve multi-beam access at arbitrary angles. Optical phased array (OPA) technology can not only achieve beam agility, inertia-free rapid scanning, flexible beam access, and high-precision beam control, but also achieve arbitrary beamforming. Furthermore, OPA devices are small in size, low in power consumption, lightweight, and easy to integrate, making them promising for applications in next-generation space laser communication, lidar, and space infrared countermeasures technologies. They are also well-suited for special platforms such as airborne, missile-borne, and spaceborne systems.

[0003] Currently, small deflection angles and low efficiency are the main technical bottlenecks limiting space-to-space laser communication, space-to-ground laser communication, short-range atmospheric laser communication, and quantum communication technologies. Whether it's lidar and laser collimators, laser guidance seekers and laser directed energy weapons, autonomous driving, laser communication networks, and new lidar systems, there is an unprecedented and urgent need for improved deflection angles and efficiency of space laser beams.

[0004] Currently, the deflection angle of a single optical phased array antenna is generally small, typically theoretically not exceeding ±10°. Due to manufacturing process errors and limitations in materials and equipment, the actual deflection angle is even smaller. In phased array beam deflection schemes, the deflection angle range and efficiency are generally contradictory; therefore, larger deflection angles result in lower efficiency. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a fast-response, large-angle beam deflection system for liquid crystal phased array backhaul optical paths. This system employs sub-aperture partitioning control and a beam splitting and rotating return optical path design, enabling large-angle, high-deflection-efficiency, fast-response, and low-energy-loss continuous beam deflection based on a single spatial light modulator. Furthermore, a method for beam deflection using this system is provided. Based on a spatial light modulator, a novel phase modulation algorithm using sub-aperture alternating phase gradients is employed, achieving a significant increase in the deflection angle range of a single liquid crystal phased array device.

[0006] The objective of this invention is achieved through the following technical solution: a fast-response large-angle beam deflection system for a liquid crystal phased array backhaul optical path, comprising a laser, a polarizer, a polarizing beam splitter, a Faraday rotator, a first total internal reflection prism, a liquid crystal optical phased array, a second total internal reflection prism, and a total internal reflection plane mirror.

[0007] The polarizing beam splitter is horizontally coaxial with the optical paths of the laser and polarizer. The polarizing beam splitter is rotated 45° counterclockwise about the vertical axis. The Faraday rotator is located below the polarizing beam splitter.

[0008] The first and second total internal reflection prisms have the same structure, each including a long transparent horizontal plane and multiple total reflection surfaces. The multiple total reflection surfaces are distributed in a sawtooth pattern. The long transparent horizontal planes of the first and second total internal reflection prisms are parallel and closely attached to the upper and lower sides of the liquid crystal optical phased array. The first and second total internal reflection prisms are arranged in a horizontally staggered spatial arrangement, with the first and second total internal reflection prisms offset by one total reflection surface. The line connecting the highest point of the i-th corner of the first total internal reflection prism and the lowest point of the (i+1)-th corner of the second total internal reflection prism is perpendicular to the long transparent horizontal plane of the two prisms.

[0009] The total internal reflection plane mirror serves as the total internal reflection surface for the emitted light, and is closely attached to the lower side of the liquid crystal optical phased array and the right side of the second total internal reflection prism.

[0010] The liquid crystal optical phased array is spatially divided into multiple sub-aperture working areas. Each sub-aperture corresponds to one or a pair of parallel reflecting surfaces. The monotonicity of the electronically controlled phase distribution of adjacent sub-apertures is a mirror image of each other about the center line.

[0011] The laser beam passes sequentially through a polarizer, a polarizing beam splitter, a Faraday rotator, and a liquid crystal optical phased array before entering the second total internal reflection prism. After multiple reflections between the second total internal reflection prism, the liquid crystal optical phased array, and the first total internal reflection prism, the beam exits from the last reflecting surface of the first total internal reflection prism. The beam then passes through the liquid crystal optical phased array and enters the total internal reflection plane mirror. After being reflected by the total internal reflection plane mirror, the beam returns to the first total internal reflection prism. The beam then returns along the path it entered during the beam's entry and finally exits through the polarizing beam splitter.

[0012] The polarizing beam splitter is placed on a vacuum electronically controlled rotating platform and rotated 45° counterclockwise around the vertical axis. After the S-beam from the polarizer is adjusted by the polarizing beam splitter, the polarization direction of the emitted light forms a 45° angle with the horizontal direction. In the return optical path, the return beam is polarized at -45° with the horizontal after passing through the Faraday rotator, and is transmitted out as P-beam after passing through the polarizing beam splitter.

[0013] The Faraday rotator utilizes the Faraday rotation effect to deflect the polarization direction of the S-light emitted from the polarizing beam splitter by 45°, rotating it from its original polarization direction at a 45° angle to the horizontal to a horizontal direction, and making it parallel to the direction of the liquid crystal pointer and the optical axis of the liquid crystal. In the return optical path, the return light, which is polarized in a horizontal direction, is deflected again by the Faraday rotator, and its polarization direction becomes -45° to the horizontal and is incident on the polarizing beam splitter.

[0014] Another objective of this invention is to provide a fast-response large-angle beam deflection method for the backhaul optical path of a liquid crystal phased array, which is implemented using the aforementioned beam deflection system. The specific steps are as follows:

[0015] Step 1: Construct and calibrate the beam deflection system: Construct a fast-response, large-angle beam deflection system for the return optical path according to the optical path. Adjust the laser, polarizer, and polarizing beam splitter to be in a horizontal coaxial optical path. Adjust the pitch and azimuth angles of the first and second total internal reflection prisms until the two ends of the two prisms are aligned and in the same vertical space, and the long sides of the two prisms are parallel to the transparent horizontal plane. Move the first total internal reflection prism horizontally so that the line connecting the highest point of the first corner of the first total internal reflection prism and the lowest point of the second corner of the second total internal reflection prism is perpendicular to the long side of the transparent horizontal plane. Then, adjust the laser to be incident on the long side of the transparent horizontal plane of the second total internal reflection prism. Adjust the azimuth and pitch angles of the first total internal reflection prism so that the outgoing light from the last reflecting surface of the first total internal reflection prism is parallel to the incident light from the first reflecting surface of the second total internal reflection prism. Finally, add a Faraday rotator below the polarizing beam splitter.

[0016] A refractive index matching liquid is uniformly coated on the outer side of the glass substrates on both sides of the liquid crystal optical phased array. Then, it is placed between the first total internal reflection prism and the second total internal reflection prism. The first total internal reflection prism is moved vertically so that the liquid crystal optical phased array is in close contact with the long side transparent horizontal plane of the two prisms. Then, it is cured by ultraviolet light.

[0017] Place a total internal reflection plane mirror in close contact with the lower substrate glass of the liquid crystal optical phased array and the right side of the second total internal reflection prism, and cure it with ultraviolet light.

[0018] Step 2: Set device parameters and operating wavelength: Set the spatial period of the liquid crystal device array to d, the operating wavelength to λ, and the thickness L of the Faraday rotator medium and the magnetic flux density component B.

[0019] Step 3: Set the polarization rotation angle of the Faraday rotator: The Faraday effect rotation angle θ = VBL, where V is the Feld constant. The single-direction rotation angle deflection is calculated to be 45° based on the specific parameters set.

[0020] Step 4: Set the target beam deflection angle, the number of sub-apertures, and the number of sub-aperture array elements: Set the target beam deflection angle to θ.xy =(θ x θ y The number of sub-apertures is N, and the number of sub-aperture array elements is M;

[0021] Step 5: Calculate the two-dimensional phase modulation of the return target angle beam corresponding to the sub-aperture: Based on the right-hand Cartesian coordinate system, the phase at the near-field two-dimensional spatial coordinates (x′, y′) in the nth sub-aperture region is:

[0022]

[0023] in:

[0024]

[0025] Where k0 is the spatial frequency of the beam, θ x (n) and θ y (n) represent the two-dimensional spatial angle θ xy The deflection angles corresponding to the nth sub-aperture in the one-dimensional directions of x′ and y′ respectively;

[0026] The incident light amplitude is A. After the return reflected light passes through 2N sub-apertures, the near field E of the outgoing light at the coordinates (x′, y′) of the first sub-aperture is... near The relationship between (x′, y′), total phase φ(x′, y′), and amplitude A(x′, y′) is expressed as follows:

[0027]

[0028] Among them, T n Let be the laser transmittance of the nth sub-aperture of the liquid crystal optical phased array (6).

[0029] Step 6: Load the phase modulation signal: According to the phase-voltage mapping table of the spatial light modulator, find A(x′, y′) and A(x′, y′) for the near-field coordinate point (x′, y′). The corresponding voltage values ​​are obtained, and a voltage matrix for all regions of the liquid crystal optical phased array is generated. Finally, these are merged into a complete voltage bitmap, which is then loaded into the liquid crystal optical phased array modulator to achieve large-angle beam deflection based on a single liquid crystal phased array.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention discloses a fast-response, large-angle beam deflection system for a liquid crystal phased array backhaul optical path. Based on a single liquid crystal optical phased spatial light modulator, it employs sub-aperture partitioning control and a beam splitting and rotating backhaul optical path design to achieve continuous spatial superposition of laser near-field phases. The optical path design is simple and can achieve large-angle, high-deflection-efficiency, fast-response, and low-energy-loss programmable continuous beam deflection based on a single spatial light modulator. This method is applicable to large-angle beam deflection using other types of laser spatial light modulators, metasurface modulators, waveguide modulators, and microwave phased arrays.

[0032] 2. This invention supports continuously adjustable deflection angles and 2π-positioned outgoing light approach phase even when the phase modulation depth of a device is extremely low or less than 2π. It solves the bottleneck problem that low-refractive-index-difference liquid crystal materials cannot be used as phased array materials under the same thickness.

[0033] 3. This invention, through the reflection return optical path design, can achieve the same number of beam phase information modulation and superposition while reducing the size and length of the sub-aperture device. It also lowers the requirements for device fabrication and device cascading, and optimizes the beam wavefront difference caused by the reduction in processing errors.

[0034] 4. Through beam splitting and optical rotation design, this invention ensures that the reflected return beam can be completely transmitted at the PBS, which greatly reduces the energy loss of the laser beam after it enters the spatial light modulator twice due to the reflected return optical path. This alleviates the high power requirements of the laser and the system isolation requirements in specific working scenarios to a certain extent.

[0035] 5. The system debugging steps of this invention are simple. Based on a single device, it ensures the consistency of each sub-aperture region, greatly reducing the alignment requirements of ordinary cascaded structures and the distortion problems caused by wavefront differences. Based on a spatial light modulator, a novel phase modulation algorithm with alternating phase gradient of sub-apertures is adopted, which realizes the ability to multiply the deflection angle range of a single liquid crystal phased array device. This can meet the needs of new-type lidar for large field of view and fast target tracking and aiming. Its large deflection angle and fast response capability provide theoretical feasibility support and technical guarantee for the realization of free space laser communication networking. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the fast-response large-angle beam deflection system of the liquid crystal phased array return optical path of the present invention;

[0037] Figure 2 This is a schematic diagram of the total internal reflection prism structure of the present invention;

[0038] Figure 3 This is a diagram showing the sub-aperture partitioning structure and near-field distribution of the liquid crystal phased array (OPA) in this embodiment;

[0039] Figure 4 This is a flowchart of the large-angle beam deflection method for liquid crystal phased arrays according to the present invention.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1: Laser; 2: Polarizer; 3: Polarizing beam splitter; 4: Faraday rotator; 5: First total internal reflection prism; 5-1: First total internal reflection surface of the first total internal reflection prism; 5-8: Eighth total internal reflection surface of the first total internal reflection prism; 5-9: Long side transparent horizontal plane of the first total internal reflection prism; 6: Liquid crystal optical phased array; 7: Second total internal reflection prism; 7-1: First total internal reflection surface of the second total internal reflection prism; 7-2: Second total internal reflection surface of the second total internal reflection prism; 7-9: Long side transparent horizontal plane of the second total internal reflection prism; 8: Total internal reflection plane mirror. Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0043] like Figure 1 As shown, the liquid crystal phased array backhaul optical path fast response large-angle beam deflection system of the present invention includes a laser 1, a polarizer 2, a polarizing beam splitter (PBS) 3, a Faraday rotator 4, a first total internal reflection prism 5, a liquid crystal optical phased array (OPA) 6, a second total internal reflection prism 7, and a total internal reflection plane mirror 8.

[0044] The polarizing beam splitter 3 is horizontally coaxial with the optical paths of the laser 1 and the polarizer 2. The polarizing beam splitter 3 is rotated 45° counterclockwise around the vertical axis. The Faraday rotator 4 is located below the polarizing beam splitter 3, and the polarization direction of the rotating S-beam is located in the vertical optical path immediately following the polarizing beam splitter 3.

[0045] like Figure 2 As shown, the first total internal reflection prism 5 and the second total internal reflection prism 7 have the same structure, each including a long-side transparent horizontal plane and multiple total internal reflection surfaces. The multiple total internal reflection surfaces are serrated. The long-side transparent horizontal planes 5-9 (CD plane) and 7-9 (EF plane) of the first total internal reflection prism 5 and the second total internal reflection prism 7 are parallel and closely attached to the upper and lower sides of the liquid crystal optical phased array 6. The first total internal reflection prism 5 and the second total internal reflection prism 7 are arranged in a laterally staggered spatial arrangement, with the first total internal reflection prism 5 and the second total internal reflection prism 7 staggered by one total internal reflection surface. The line connecting the highest point of the i-th corner of the first total internal reflection prism 5 and the lowest point of the (i+1)-th corner of the second total internal reflection prism 7 is perpendicular to the long-side transparent horizontal plane of the two prisms. Figure 1 and Figure 2As shown, the line AB connecting the highest point A of the first edge of the first total internal reflection prism 5 and the lowest point B of the second edge of the second total internal reflection prism 7 is perpendicular to the transparent horizontal plane of the long sides of the two prisms; and so on, the line connecting the highest point of the second edge of the first total internal reflection prism 5 and the lowest point of the third edge of the second total internal reflection prism 7 is perpendicular to the transparent horizontal plane of the long sides of the two prisms...

[0046] The total internal reflection plane mirror 8 serves as the total internal reflection surface for the emitted light, and is closely attached to the lower side of the liquid crystal optical phased array 6 and the right side of the second total internal reflection prism 7.

[0047] The liquid crystal optical phased array 6 is spatially divided into multiple sub-aperture working areas. Each sub-aperture corresponds to one or a pair of parallel reflective surfaces. The monotonicity of the electronically controlled phase distribution of adjacent sub-apertures is a mirror image of each other about the center line.

[0048] The emitted beam from laser 1 passes sequentially through polarizer 2, polarizing beam splitter 3, Faraday rotator 4, and liquid crystal optical phased array 6 before entering the second total internal reflection prism 7. After multiple reflections between the second total internal reflection prism 7, liquid crystal optical phased array 6, and first total internal reflection prism 5, the beam exits from the last reflecting surface of the first total internal reflection prism 5. The emitted beam passes through the liquid crystal optical phased array 6 and enters the total internal reflection plane mirror 8. After reflection by the total internal reflection plane mirror 8 and transmission by the liquid crystal optical phased array 6, the beam returns to the first total internal reflection prism 5. Then, the beam returns along the optical path it entered during the emission process and finally exits through polarizing beam splitter 3.

[0049] The polarizing beam splitter 3 is placed on a vacuum electrically controlled rotating platform and rotated 45° counterclockwise about the vertical axis. The S-beam from the polarizer 2, after being adjusted by the polarizing beam splitter 3, achieves total internal reflection of the S-beam with almost no energy loss, resulting in a polarization direction at a 45° angle to the horizontal. In the return path, the return beam, after passing through the Faraday rotator 4, has a polarization direction at -45° to the horizontal and is transmitted as P-beam after passing through the polarizing beam splitter 3, with almost no energy loss. Furthermore, the working effect of the polarizing beam splitter is related to the wavelength selection, and if high polarization purity is required, a Gran Thompson prism can be used.

[0050] The Faraday rotator 4 utilizes the Faraday rotation effect to deflect the polarization direction of the S-light emitted from the polarizing beam splitter 3 by 45°, rotating it from the original polarization direction at a 45° angle to the horizontal direction, and making it parallel to the direction of the liquid crystal index and the optical axis of the liquid crystal. In the return optical path, the return light with the horizontal polarization direction is deflected again by the Faraday rotator 4, and the polarization direction of the light becomes -45° to the horizontal direction and is incident on the polarizing beam splitter 3.

[0051] The reflecting surfaces of the first total internal reflection prism 5 and the second total internal reflection prism 7 serve to provide light beam reflection. Their reflecting surfaces are coated with metal or dielectric films to enhance reflectivity. In this embodiment, the included angle of the reflecting surfaces is 90°, but this is not limited to 90°. The prism form is not limited to a reflecting pyramid prism, a monolithic Dowell prism, a monolithic all-metal reflector, or a discrete component adhesive structure. The size and spatial period of adjacent reflecting surfaces of the first and second total internal reflection prisms are not limited to combinations such as equal, unequal, sparse, or discrete. The forms of the first and second total internal reflection prisms 5 and 7 are not limited to one-dimensional prisms or one-dimensional reflecting surfaces; they include various forms such as reflecting arc surfaces, trihedral pyramids, and circular arc pyramids, creating multi-dimensional reflecting surfaces. Any structure that can achieve the light path reflection effect is acceptable.

[0052] The number of reflecting surface units 8 in the first total internal reflection prism 5 and the second total internal reflection prism 7 is an example and is not limited to the number of reflecting surface units or discrete prisms. For example... Figure 1 As shown, the light beam emitted from the Faraday rotator 4 enters the second total internal reflection prism 7 and first reaches the first total internal reflection surface 7-1 of the second total internal reflection prism. The first total internal reflection surface 7-1 performs total internal reflection on the light beam, which then exits to the second total internal reflection surface 7-2. Reflected by the second total internal reflection surface 7-2, the light beam enters the liquid crystal optical phased array 6. After passing through the liquid crystal optical phased array 6, the light beam exits to the first total internal reflection prism first total internal reflection surface 5-1. Reflected by the first total internal reflection surface 5-1, the light beam exits to the second total internal reflection surface 5-2. Reflected again by the second total internal reflection surface 5-2, the light beam exits the liquid crystal optical phased array 6 and enters the second total internal reflection prism 6. The light beam is reflected sequentially through the third total reflection surface 7-3 of the total internal reflection prism, the fourth total reflection surface 7-4 of the second total internal reflection prism, the third total reflection surface 4-3 of the first total internal reflection prism, the fourth total reflection surface 4-4 of the first total internal reflection prism, the fifth total reflection surface 7-5 of the second total internal reflection prism, the sixth total reflection surface 7-6 of the second total internal reflection prism, the fifth total reflection surface 5-5 of the first total internal reflection prism, the sixth total reflection surface 5-6 of the first total internal reflection prism, the seventh total reflection surface 7-7 of the second total internal reflection prism, the eighth total reflection surface 7-8 of the second total internal reflection prism, the seventh total reflection surface 5-7 of the first total internal reflection prism, and the eighth total reflection surface 5-8 of the first total internal reflection prism. Finally, it exits from the eighth total reflection surface 5-8 of the first total internal reflection prism, passes through the liquid crystal optical phased array 6, and enters the total internal reflection plane mirror 8. After being reflected by the total internal reflection plane mirror 8 and passing through the liquid crystal optical phased array 6, it returns to the eighth total reflection surface 5-8 of the first total internal reflection prism, and then returns along the incident light path.

[0053] Because the total reflection surfaces of the two reflecting prisms in this embodiment are uniformly distributed symmetrical structures, the sub-aperture sizes of the liquid crystal phased array (OPA) are the same, such as... Figure 3As shown, the sub-apertures are uniformly distributed on the liquid crystal phased array, denoted as 6-1 to 6-9.

[0054] The fast-response large-angle beam deflection method for the backhaul optical path of a liquid crystal phased array of the present invention is implemented using the aforementioned beam deflection system, and the specific process is as follows: Figure 4 As shown, the specific steps are as follows:

[0055] Step 1: Construct and calibrate the beam deflection system: Construct a fast-response, large-angle beam deflection system for the return optical path according to the optical path. Adjust the laser 1, polarizer 2, and polarizing beam splitter 3 into a horizontal coaxial optical path. Adjust the pitch and azimuth angles of the first total internal reflection prism 5 and the second total internal reflection prism 7 until the two ends of the prisms are level and in the same vertical space (i.e., from...). Figure 1 In the middle view, the two prisms are aligned front and back respectively, and the long sides of the two prisms are parallel to the transparent horizontal plane; the first total internal reflection prism 5 is moved horizontally so that the line connecting the highest point of the first corner of the first total internal reflection prism 5 and the lowest point of the second corner of the second total internal reflection prism 7 is perpendicular to the long side of the transparent horizontal plane of the prism; then the laser is adjusted to be incident on the long side of the transparent horizontal plane of the second total internal reflection prism 7, and the azimuth and elevation angles of the first total internal reflection prism 5 are adjusted so that the light emitted from the last reflecting surface of the first total internal reflection prism 5 is parallel to the incident light from the first reflecting surface of the second total internal reflection prism; then a Faraday rotator 4 is added below the polarizing beam splitter prism 3;

[0056] The refractive index matching liquid is evenly coated on the outer side of the glass substrates on both sides of the liquid crystal optical phased array 6. Then it is placed between the first total internal reflection prism 5 and the second total internal reflection prism 7. The first total internal reflection prism 5 is moved vertically so that the liquid crystal optical phased array 6 is in close contact with the long side transparent horizontal surface of the two prisms. Then it is cured by ultraviolet light.

[0057] Place the total internal reflection plane mirror 8 in close contact with the lower substrate glass of the liquid crystal optical phased array 6 and the right side of the second total internal reflection prism 7, and cure it with ultraviolet light.

[0058] Step 2: Set device parameters and operating wavelength: Set the spatial period of the liquid crystal device array to d, the operating wavelength to λ, and the thickness L of the Faraday rotator medium and the magnetic flux density component B.

[0059] Step 3: Set the polarization rotation angle of the Faraday rotator: The Faraday effect rotation angle θ = VBL, where V is the Verdet constant. The single-direction rotation angle deflection is calculated to be 45° based on the specific parameters set.

[0060] Step 4: Set the target beam deflection angle, the number of sub-apertures, and the number of sub-aperture array elements: Set the target beam deflection angle to θ. xy =(θ x θ yThe number of sub-apertures is N=9, and the number of sub-aperture array elements is M;

[0061] The system parameters built in this embodiment are shown in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] After the system is built, specific modulation information is loaded onto the spatial light modulator of the liquid crystal phased array, and the light field distribution characteristics of the outgoing light are observed. In the initial state, the liquid crystal phased array only has an initial small anchoring angle amplitude. Since the anchoring angle is consistent, the propagation direction of its outgoing light is in phase and parallel to the incident light. At this time, the system calibration is completed, the spatial position and state of the system are locked, the position of the outgoing light is recorded and marked as the far-field center 0 point;

[0066] Step 5: Calculate the two-dimensional phase modulation of the return target angle beam corresponding to the sub-aperture: Based on the right-hand Cartesian coordinate system, the phase at the near-field two-dimensional spatial coordinates (x′, y′) in the nth sub-aperture region is:

[0067]

[0068] in:

[0069]

[0070] Where k0 is the spatial frequency of the beam, θ x (n) and θ y (n) represent the two-dimensional spatial angle θ xy The deflection angles corresponding to the nth sub-aperture in the one-dimensional directions of x′ and y′ respectively;

[0071] The incident light amplitude is A. After the return reflected light passes through 2N sub-apertures, the near field E of the outgoing light at the coordinates (x′, y′) of the first sub-aperture is... near The relationship between (x′, y′), total phase φ(x′, y′), and amplitude A(x′, y′) is expressed as follows:

[0072]

[0073] Among them, T n Let be the laser transmittance of the nth sub-aperture of the liquid crystal optical phased array (6).

[0074] Step 6: Load the phase modulation signal: According to the phase-voltage mapping table of the spatial light modulator, find A(x′, y′) and A(x′, y′) for the near-field coordinate point (x′, y′). The corresponding voltage values ​​are obtained, and a voltage matrix for all regions of the liquid crystal optical phased array is generated. Finally, these are merged into a complete voltage bitmap, which is then loaded into the liquid crystal optical phased array modulator to achieve large-angle beam deflection based on a single liquid crystal phased array.

[0075] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A liquid crystal phased array backhaul optical path fast-response large-angle beam deflection system, characterized in that, It includes a laser (1), a polarizer (2), a polarizing beam splitter (3), a Faraday rotator (4), a first total internal reflection prism (5), a liquid crystal optical phased array (6), a second total internal reflection prism (7), and a total internal reflection plane mirror (8); The polarizing beam splitter (3) is horizontally coaxial with the optical paths of the laser (1) and the polarizer (2). The polarizing beam splitter (3) is rotated 45° counterclockwise around the vertical axis. The Faraday rotator (4) is located below the polarizing beam splitter (3). The first total reflection prism (5) and the second total reflection prism (7) have the same structure, both including a long side transparent horizontal plane and multiple total reflection surfaces. The multiple total reflection surfaces are distributed in a sawtooth pattern. The long side transparent horizontal planes of the first total reflection prism (5) and the second total reflection prism (7) are parallel and closely attached to the upper and lower sides of the liquid crystal optical phased array (6). The first total reflection prism (5) and the second total reflection prism (7) are arranged in a horizontally staggered spatial arrangement. The first total reflection prism (5) and the second total reflection prism (7) are staggered by a total reflection surface. The line connecting the highest point of the i-th corner of the first total reflection prism (5) and the lowest point of the i+1-th corner of the second total reflection prism (7) is perpendicular to the long side transparent horizontal plane of the two prisms. The total internal reflection plane mirror (8) serves as the total internal reflection surface for the emitted light, and is closely attached to the lower side of the liquid crystal optical phased array (6) and the right side of the second total internal reflection prism (7). The liquid crystal optical phased array (6) is spatially divided into multiple sub-aperture working areas. Each sub-aperture corresponds to one or a pair of parallel reflective surfaces. The monotonicity of the electronically controlled phase distribution of adjacent sub-apertures is a mirror image of each other about the center line. The emitted beam from the laser (1) passes sequentially through the polarizer (2), polarizing beam splitter (3), Faraday rotator (4), and liquid crystal optical phased array (6) before entering the second total internal reflection prism (7). After folding back and forth between the second total internal reflection prism (7), the liquid crystal optical phased array (6), and the first total internal reflection prism (5), the emitted beam exits from the last reflecting surface of the first total internal reflection prism (5). The emitted beam passes through the liquid crystal optical phased array (6) and enters the total internal reflection plane mirror (8). After being reflected by the total internal reflection plane mirror (8), the beam returns to the first total internal reflection prism (5). Then, the beam returns along the optical path it entered, and finally exits through the polarizing beam splitter (3).

2. The liquid crystal phased array backhaul optical path fast-response large-angle beam deflection system according to claim 1, characterized in that, The polarizing beam splitter (3) is placed on a vacuum electronically controlled rotating platform and rotated 45° counterclockwise around the vertical axis. After the S-beam from the polarizer (2) is adjusted by the polarizing beam splitter (3), the polarization direction of the emitted light forms a 45° angle with the horizontal direction. In the return optical path, the return beam is polarized at -45° to the horizontal after passing through the Faraday rotator (4), and is transmitted out as P-beam after passing through the polarizing beam splitter (3).

3. The liquid crystal phased array backhaul optical path fast-response large-angle beam deflection system according to claim 2, characterized in that, The Faraday rotator (4) utilizes the Faraday rotation effect to deflect the polarization direction of the S-light emitted from the polarizing beam splitter (3) by 45°, rotating it from the original polarization direction at a 45° angle to the horizontal direction, and making it parallel to the direction of the liquid crystal pointer and the liquid crystal optical axis. In the return optical path, the return light with the horizontal polarization direction is deflected again by the Faraday rotator (4), and the polarization direction of the light becomes -45° to the horizontal direction and is incident on the polarizing beam splitter (3).

4. A method for fast-response large-angle beam deflection in the return optical path of a liquid crystal phased array, implemented using the beam deflection system described in any one of claims 1 to 3, characterized in that... The specific steps are as follows: Step 1: Construct and calibrate the beam deflection system: Construct a fast-response, large-angle beam deflection system for the return optical path according to the optical path. Adjust the laser (1), polarizer (2), and polarizing beam splitter (3) in a horizontal coaxial optical path. Adjust the pitch and azimuth angles of the first total internal reflection prism (5) and the second total internal reflection prism (7) until the two ends of the two prisms are level and in the same vertical space, and the long sides of the two prisms are parallel to the transparent horizontal planes. Move the first total internal reflection prism (5) horizontally so that the first total internal reflection prism... The line connecting the highest point of the first edge of the mirror (5) and the lowest point of the second edge of the total internal reflection prism (7) is perpendicular to the long side transparent horizontal plane of the prism; then adjust the laser to be incident on the long side transparent horizontal plane of the second total internal reflection prism (7), and adjust the azimuth and elevation angles of the first total internal reflection prism (5) so that the outgoing light from the last reflecting surface of the first total internal reflection prism (5) is parallel to the incident light from the first reflection surface of the second total internal reflection prism; then add a Faraday rotator (4) below the polarizing beam splitter (3); The refractive index matching liquid is evenly coated on the outer side of the glass substrate on both sides of the liquid crystal optical phased array (6), and then placed between the first total reflection prism (5) and the second total reflection prism (7). The first total reflection prism (5) is moved vertically so that the liquid crystal optical phased array (6) is in close contact with the long side transparent horizontal surface of the two prisms, and then cured by ultraviolet light. Place the total internal reflection plane mirror (8) in close contact with the lower substrate glass of the liquid crystal optical phased array (6) and the right side of the second total internal reflection prism (7), and cure it with ultraviolet light. Step 2: Set device parameters and operating wavelength: Set the spatial period of the liquid crystal device array to d, the operating wavelength to λ, and the thickness L of the Faraday rotator medium and the magnetic flux density component B. Step 3: Set the polarization rotation angle of the Faraday rotator: The Faraday effect rotation angle θ = VBL, where V is the Feld constant. The single-direction rotation angle deflection is calculated to be 45° based on the specific parameters set. Step 4: Set the target beam deflection angle, the number of sub-apertures, and the number of sub-aperture array elements: Set the target beam deflection angle to θ. xy =(θ x ,θ y The number of sub-apertures is N, and the number of sub-aperture array elements is M; Step 5: Calculate the two-dimensional phase modulation of the return target angle beam corresponding to the sub-aperture: Based on the right-hand Cartesian coordinate system, the phase at the near-field two-dimensional spatial coordinates (x′, y′) in the nth sub-aperture region is: in: Where k0 is the spatial frequency of the beam, θ x (n) and θ y (n) represent the two-dimensional spatial angle θ xy The deflection angles corresponding to the nth sub-aperture in the one-dimensional directions of x′ and y′ respectively; The incident light amplitude is A. After the return reflected light passes through 2N sub-apertures, the near field E of the outgoing light at the coordinates (x′, y′) of the first sub-aperture is... nerar The relationship between (x′,y′), total phase φ(x′,y′), and amplitude A(x′,y′) is expressed as follows: Among them, T n Let be the laser transmittance of the nth sub-aperture of the liquid crystal optical phased array (6); Step 6: Load the phase modulation signal: According to the phase-voltage mapping table of the spatial light modulator, find A(x′,y′) and A(x′,y′) of the near-field coordinate point (x′,y′). The corresponding voltage values ​​are obtained, and a voltage matrix is ​​generated for all regions of the liquid crystal optical phased array. Finally, these are merged into a complete voltage bitmap, which is then loaded into the liquid crystal optical phased array modulator to achieve large-angle beam deflection based on a single liquid crystal phased array.

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