A two-dimensional beam deflection structure with high diffraction energy distribution uniformity

Abstract

This invention relates to a two-dimensional beam deflection structure with high uniformity of diffraction energy distribution, belonging to the field of non-mechanical beam manipulation technology. It addresses the technical problems of large differences in diffraction efficiency and uneven energy distribution in existing cascaded structures under different angular orientations. The structure includes N horizontal one-dimensional diffraction sub-units with grating periods along the horizontal direction and N vertical one-dimensional diffraction sub-units with grating periods along the vertical direction. The horizontal one-dimensional diffraction sub-units are arranged in ascending order of their grating periods, and the vertical one-dimensional diffraction sub-units are also arranged in ascending order of their grating periods. The cascading order between the horizontal and vertical one-dimensional diffraction sub-units is arbitrarily set. Through optimized design of the grating periods of the one-dimensional diffraction sub-units within each dimension and the cascading order between different dimensions, this invention can reduce the difference in diffraction efficiency under different angular orientations and significantly improve the uniformity of the total diffraction efficiency distribution within a wide-angle scanning range.

Description

Technical Field

[0001] This invention belongs to the field of non-mechanical beam manipulation technology, specifically relating to a two-dimensional beam deflection structure with high uniformity of diffraction energy distribution. Background Technology

[0002] With the rapid development of fields such as laser communication, airborne radar, UAV beam control, lidar, augmented reality / virtual reality, and biological microscopy, there are increasing demands for wide-angle, compact, low-power, fast-response, and high-energy-efficiency beam deflection technology. Mechanical beam deflection technologies (such as gimbals) have inherent drawbacks such as large size, high power consumption, and slow response; the optical aperture of fast-reflecting mirrors in microelectromechanical systems (MEMS) is limited, making it difficult to support wide-angle scanning. Non-mechanical beam deflection technologies, especially those based on liquid crystal polarization gratings, have attracted much attention due to their advantages such as compact structure, low power consumption, fast response, and large optical aperture.

[0003] Liquid crystal polarization gratings (LCDs) are geometrically phase optical elements whose theoretical diffraction efficiency can approach 100% under half-wave conditions. However, LCDs used for wide-angle scanning fall under the category of Bragg gratings, and their diffraction efficiency is highly dependent on the degree to which the incident angle deviates from the Bragg condition. Furthermore, to achieve wide-angle beam deflection, multiple LCDs with different grating periods are typically cascaded to form a two-dimensional beam deflection structure. With the increase in the number of cascaded sub-elements and the expansion of the field of view, the difference in total diffraction efficiency at different angular directions increases significantly, especially the energy imbalance between the central and edge regions, which severely restricts their application in fields such as laser communication where high energy stability is required.

[0004] While existing research has focused on the diffraction efficiency of cascaded structures, most studies concentrate on the performance analysis of a single subunit or efficiency compensation under specific fields of view and sequences. They have not yet revealed that cascaded structures can achieve high diffraction energy distribution uniformity across a wide-angle scanning range, regardless of whether the transmission or reception mode is used. Summary of the Invention

[0005] The present invention aims to provide a two-dimensional beam deflection structure with high uniformity of diffraction energy distribution, so as to solve the technical problems of large differences in diffraction efficiency and uneven energy distribution of existing cascade structures under different angular pointing.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A two-dimensional beam deflection structure with high uniformity of diffraction energy distribution includes N horizontal one-dimensional diffraction sub-units and N vertical one-dimensional diffraction sub-units. The grating period of the horizontal one-dimensional diffraction sub-units is along the horizontal direction, and the grating period of the vertical one-dimensional diffraction sub-units is along the vertical direction.

[0008] Each of the horizontal one-dimensional diffraction sub-units is arranged in order of increasing grating period, and each of the vertical one-dimensional diffraction sub-units is arranged in order of increasing grating period. The cascading order between the horizontal one-dimensional diffraction sub-units and the vertical one-dimensional diffraction sub-units is arbitrarily set.

[0009] The beneficial effects of this invention are as follows:

[0010] (1) This invention proposes a two-dimensional beam deflection structure with high uniformity of diffraction energy distribution. In this two-dimensional beam deflection structure, the one-dimensional diffraction sub-units in each dimension (horizontal and vertical) follow the order of increasing grating period, while the cascading order between different dimensions can be arbitrarily set. This independence of the cascading order between the two dimensions will significantly reduce the parameter freedom in the optimization design of the two-dimensional beam deflection system and the assembly and alignment difficulty in the system construction process, which is beneficial to engineering applications. At the same time, by optimizing the cascading order, this invention can reduce the difference in diffraction efficiency under different angular pointing, significantly improve the uniformity of the total diffraction efficiency distribution in the wide-angle scanning range, and meet the current demand for high uniformity of the total diffraction efficiency distribution of the wide-angle cascading structure.

[0011] (2) The applicability of the two-dimensional beam deflection structure of the present invention is not affected by the deflection angle range, the angle pointing resolution and the number of one-dimensional diffraction sub-units, nor by the size of the grating period of the one-dimensional diffraction sub-units.

[0012] (3) The two-dimensional beam deflection structure of the present invention is effective in both transmission and reception modes. This structure is particularly suitable for common optical path systems that integrate transmission and reception, such as UAVs, small satellites and other platforms with strict limitations on size, weight and power consumption. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the two-dimensional beam deflection system formed by cascading one-dimensional diffraction sub-units in the horizontal and vertical dimensions of the present invention.

[0014] Figure 2 The diagram shows a comparison of the total diffraction efficiency distribution with the angular pointing array obtained by using the cascaded structure proposed in this invention and the traditional cascaded structure, respectively.

[0015] Explanation of reference numerals in the attached figures: 1. Horizontal one-dimensional diffraction subunit; 2. Vertical one-dimensional diffraction subunit; 3. Two-dimensional beam deflection structure; M. Cascaded measure, indicating that a cascaded operation is performed on any relative position of N horizontal one-dimensional diffraction subunits 1 and N vertical one-dimensional diffraction subunits 2. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0017] Example 1

[0018] like Figure 1 As shown, this embodiment provides a geometric phase grating cascade structure with high diffraction energy distribution uniformity over a wide-angle scanning range, namely a two-dimensional beam deflection structure 3, which is particularly suitable for beam deflection systems where the receiving mode and the transmitting mode can share the same optical path. Specifically, the two-dimensional beam deflection structure 3 includes N horizontal one-dimensional diffraction sub-units 1 and N vertical one-dimensional diffraction sub-units 2, and the grating period of each horizontal one-dimensional diffraction sub-unit 1 is along the horizontal direction, and the grating period of each vertical one-dimensional diffraction sub-unit 2 is along the vertical direction.

[0019] In the two-dimensional beam deflection structure 3, the one-dimensional diffraction sub-units in each dimension (horizontal dimension and vertical dimension) must follow the order of increasing grating period, while the cascading order between different dimensions can be arbitrarily set. Specifically, each horizontal one-dimensional diffraction sub-unit 1 is arranged in the order of increasing grating period, and each vertical one-dimensional diffraction sub-unit 2 is arranged in the order of increasing grating period. However, when cascading, the cascading order between the horizontal one-dimensional diffraction sub-unit 1 and the vertical one-dimensional diffraction sub-unit 2 is arbitrarily set, that is, the horizontal one-dimensional diffraction sub-unit 1 and the vertical one-dimensional diffraction sub-unit 2 are set independently of each other and are not limited to a specific order.

[0020] In this embodiment, the horizontal one-dimensional diffraction subunit 1 consists of an electrically controlled liquid crystal waveplate and a passive geometric phase grating with a grating period along the horizontal direction. The vertical one-dimensional diffraction subunit 2 consists of an electrically controlled liquid crystal waveplate and a passive geometric phase grating with a grating period along the vertical direction. The passive geometric phase grating includes all geometric phase gratings that follow Bragg diffraction characteristics, such as liquid crystal polarization gratings. The geometric phase distribution of the passive geometric phase grating lies in its thickness direction within the normal plane, allowing it to couple most of the circularly polarized incident light energy to the first order at half-wave thickness. By adjusting the applied voltage of the electrically controlled liquid crystal waveplate to maintain or switch the incident light circular polarization chirality of the passive geometric phase grating, the beam deflection direction of the one-dimensional diffraction subunit (+1st order or -1st order) can be changed. Therefore, by cascading and constructing a two-dimensional beam deflection structure 3, and by traversing the operating states of all electrically controlled liquid crystal waveplates in N horizontal one-dimensional diffraction subunits 1 and N vertical one-dimensional diffraction subunits 2, a beam deflection structure with a 2×2... N A discrete diffraction array pointing at several angles. Because the cascaded scheme requires that the incident angles of adjacent one-dimensional diffraction sub-units satisfy the grating equation, thus this 2×2 NThe degree to which the incident angles accumulated along the diffraction paths corresponding to different angles deviate from the Bragg condition will inevitably vary, ultimately resulting in differences in the total diffraction efficiency of the two-dimensional beam deflection structure 3 across different angles. Therefore, the uniformity of the total diffraction efficiency distribution of the two-dimensional beam deflection structure 3 across different angles can be significantly improved by changing the degree to which the incident angles of the one-dimensional diffraction subunits deviate from the Bragg condition.

[0021] This embodiment proposes a two-dimensional beam deflection structure with high uniformity of diffraction energy distribution. In this structure, the one-dimensional diffraction sub-units within each dimension follow an increasing order of grating period, while the cascading order between different dimensions can be arbitrarily set. This independence of the cascading order between the two dimensions significantly reduces the degree of parameter freedom in the optimized design of the two-dimensional beam deflection system and the assembly and alignment difficulties during system construction, which is beneficial for engineering applications. Furthermore, through the optimized design of the grating period of the one-dimensional diffraction sub-units within each dimension and the cascading order between different dimensions, the passive geometric phase grating with the smallest grating period bears the weakest degree of tilted incidence. This measure can maximize the suppression of Bragg condition deviations in the angular pointing of the array edge, thereby significantly alleviating the difference in total diffraction efficiency between the angular pointing array edge and the central region. Therefore, compared with traditional cascaded structures, the two-dimensional beam deflection structure proposed in this embodiment can effectively improve the uniformity of the total diffraction efficiency distribution within the wide-angle scanning range, meeting the current requirement for high uniformity of the total diffraction efficiency distribution in wide-angle cascaded structures. Furthermore, the applicability of the two-dimensional beam deflection structure in this embodiment is unaffected by the deflection angle range, angular pointing resolution, or the number of one-dimensional diffraction sub-units, nor by the grating period size of the horizontal one-dimensional diffraction sub-unit 1 or the vertical one-dimensional diffraction sub-unit 2. The two-dimensional beam deflection structure of this embodiment is effective in both transmission and reception modes. This structure is particularly suitable for common optical path systems where the transmission and reception optical paths are integrated, such as platforms with strict limitations on size, weight, and power consumption, such as UAVs and small satellites.

[0022] Example 2

[0023] This embodiment demonstrates the process of specific calculation and verification using the two-dimensional beam deflection structure of the present invention.

[0024] In this embodiment, the parameters of the two-dimensional beam deflection structure 3 are set as follows:

[0025] Passive geometric phase grating selection liquid crystal polarization grating;

[0026] Angle deflection range: 50° × 50°;

[0027] The vacuum wavelength is 660 nm;

[0028] The number N of the horizontal one-dimensional diffraction subunit 1 is 3, and the grating diffraction angles of these 3 subunits under vertical incidence are A1, A2, and A3, respectively. Since the grating period must increase in the horizontal dimension, it can be known from the relationship between the grating period and the grating diffraction angle that the grating diffraction angle satisfies A1>A2>A3.

[0029] The number N of the vertical one-dimensional diffraction subunit 2 is 3, and the grating diffraction angles of these 3 subunits under vertical incidence are B1, B2, and B3, respectively, which also satisfy B1>B2>B3.

[0030] Based on all the parameters in this embodiment, when applying the cascaded structure of the present invention, the one-dimensional diffraction subunits within each dimension must follow an increasing order of grating period, while the cascade order between different dimensions can be arbitrarily set. Therefore, according to the cascaded structure proposed by the present invention, its cascade order can be divided into three types: completely interlaced, fractal cascaded, and a mixture of fractal cascaded and interlaced. To better illustrate the cascade order, this embodiment uses A1, A2, A3, B1, B2, and B3 to represent the diffraction angles of the grating under perpendicular incidence.

[0031] In this embodiment, A1, A2, A3 and B1, B2, B3 can take various numerical combinations. As an example, A1 = B1 = 14.28°, A2 = B2 = 7.14°, and A3 = B3 = 3.57° are taken. It should be noted that these angle values ​​are for demonstration purposes only; in practical applications, they can be determined based on the required deflection range, wavelength, and grating equation. The grating diffraction angle sequences under perpendicular incidence are as follows: (The original text contains some inconsistencies and unclear grammatical structures. A more accurate translation would require the full context.)

[0032] Fully staggered cascade configuration: {A1, B1, A2, B2, A3, B3} (i.e., {14.28°, 14.28°, 7.14°, 7.14°, 3.57°, 3.57°}).

[0033] Fully fractal cascaded: {A1, A2, A3, B1, B2, B3} (i.e., {14.28°, 7.14°, 3.57°, 14.28°, 7.14°, 3.57°}).

[0034] Fractal dimension and staggered hybrid cascade method: {A1, B1, A2, A3, B2, B3} (i.e., {14.28°, 14.28°, 7.14°, 3.57°, 7.14°, 3.57°}).

[0035] Based on the traditional cascaded structure: {A3, A2, A1, B3, B2, B1} (i.e., {3.57°, 7.14°, 14.28°, 3.57°, 7.14°, 14.28°}).

[0036] Based on the above four cascade sequences, the distribution of the total diffraction efficiency with respect to the angular orientation of the array is as follows: Figure 2 As shown. From Figure 2 As can be seen, the total diffraction efficiency distributions among the three cascade sequences determined by the two-dimensional beam deflection structure proposed according to this invention are almost identical. This is because these three cascade sequences belong to the same category, and the distribution of total diffraction efficiency is not sensitive to changes in this category of cascade sequences. Furthermore, from Figure 2 It can also be seen that when the traditional cascaded structure is adjusted to the two-dimensional beam deflection structure of the present invention, the maximum change in the total diffraction efficiency with the angle pointing array decreases from 41.57% to 13.08%. The reason why the uniformity can be improved so significantly is that in the two-dimensional beam deflection structure of the present invention, for the angle pointing of the edge of the diffraction array, the one-dimensional diffraction sub-unit with a smaller grating period encounters a smaller Bragg condition deviation.

[0037] As can be seen from this embodiment, the two-dimensional beam deflection structure with high diffraction energy distribution uniformity proposed in this invention can significantly improve the distribution uniformity of total diffraction efficiency, and will play an important role, especially when the performance of both the emission mode and the receiving mode needs to be considered.

[0038] The two-dimensional beam deflection structure proposed in this invention can meet the current demand for high uniformity of total diffraction efficiency distribution in wide-angle cascade structures, providing key technical support for its further application in fields such as laser communication, airborne radar, UAV beam control, lidar, augmented reality / virtual reality, and biological microscopy.

[0039] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0040] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A two-dimensional beam deflection structure with high diffraction energy distribution uniformity, characterized in that, It includes N horizontal one-dimensional diffraction sub-units (1) and N vertical one-dimensional diffraction sub-units (2), wherein the grating period of the horizontal one-dimensional diffraction sub-unit (1) is along the horizontal direction, and the grating period of the vertical one-dimensional diffraction sub-unit (2) is along the vertical direction. Each of the horizontal one-dimensional diffraction sub-units (1) is arranged in order of increasing grating period, and each of the vertical one-dimensional diffraction sub-units (2) is arranged in order of increasing grating period. The cascading order between the horizontal one-dimensional diffraction sub-units (1) and the vertical one-dimensional diffraction sub-units (2) is arbitrarily set.

2. The two-dimensional beam deflection structure with high diffraction energy distribution uniformity according to claim 1, characterized in that, Each of the horizontal one-dimensional diffraction sub-units (1) consists of an electrically controlled liquid crystal waveplate and a passive geometric phase grating with a grating period along the horizontal direction, and each of the vertical one-dimensional diffraction sub-units (2) consists of an electrically controlled liquid crystal waveplate and a passive geometric phase grating with a grating period along the vertical direction.

3. A two-dimensional beam deflection structure with high diffraction energy distribution uniformity according to claim 2, characterized in that, The passive geometric phase grating includes all geometric phase gratings that follow Bragg diffraction properties.

4. A two-dimensional beam deflection structure with high diffraction energy distribution uniformity according to claim 3, characterized in that, The passive geometric phase grating is a liquid crystal polarization grating.

5. A two-dimensional beam deflection structure with high diffraction energy distribution uniformity according to claim 1, characterized in that, The two-dimensional beam deflection structure is configured in a common optical path system that integrates the transmitting and receiving optical paths.

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