A multi-node structured light field generation device with interactive network characteristics

Abstract

The embodiment of the application discloses a kind of multi-node structure light field generation devices with interactive network characteristics, including transparent substrate and multiple diffraction modulation units, diffraction modulation unit is sheet fork grating, the number of sheet fork grating is at least three pieces, sheet fork grating is integrated and engraved on the surface of transparent substrate by laser direct writing technology, each sheet fork grating has independent light field phase modulation function, from the first engraved sheet fork grating, from below to above, each sheet fork grating is rotated around the axis in the same direction relative to the sheet fork grating of adjacent lower piece, and a constant misregistration angle is generated, the misregistration angle refers to the relative rotation angle between two adjacent sheet fork gratings, the product of the number of sheet fork gratings and misregistration angle is less than or equal to 360 °, the advantage is that multi-node structure light field with interactive network characteristics can be realized in high-dimensional parameter space, and the types and complexity of the generated light field are enriched.

Description

Technical Field

[0001] This invention relates to a structured light field generation device, and more particularly to a multi-node structured light field generation device with interactive network characteristics. Background Technology

[0002] Structured light fields, which are light fields with customized spatial phase, amplitude, or polarization distributions, are key carriers in cutting-edge fields such as optical communication, optical manipulation, quantum information, and high-resolution imaging. Current technologies are mostly based on single or dual diffraction units, with limited degrees of freedom for manipulation, typically only enabling simple mode transitions or limited state superposition. However, on production lines for critical components such as power batteries, precision motors, and integrated die-cast body parts, multi-node structured light fields with complex spatial relationships and interactive network characteristics are needed to rapidly detect the flatness of battery modules, weld quality, or the structural integrity of large die-cast body parts.

[0003] In this multi-node structured optical field with interactive network characteristics, the incident light is modulated by a device composed of multiple diffraction modulation units, forming multiple spatially separated main energy nodes in the far field or Fourier surface; the spatial distribution skeleton of each node and the mapping law between the node topological features are constrained by and mainly determined by the overall structural symmetry of the device; among them, at least some nodes are formed by the directional degeneracy and superposition of multiple diffraction channels in a preset direction, thus distinguishing them from the multi-beam output obtained by splitting a single diffraction channel.

[0004] Currently, the mainstream techniques for generating multi-node structured light fields rely on spatial light modulators or metasurfaces. In theory, spatial light modulators and metasurfaces can generate multi-node structured light fields by loading composite holograms or solidifying phase codes.

[0005] However, spatial light modulators typically rely on external computation and electronically controlled loading, resulting in high system size and complexity. Furthermore, the coherence relationships between multiple nodes are more sensitive to drift and disturbances, and they are limited by power handling capacity, operating wavelength, and response speed. For conventional liquid crystal / silicon-based liquid crystal spatial light modulators, high optical power density conditions often lead to problems such as heat accumulation, modulation characteristic drift, and decreased operational stability. To adapt to higher power applications, existing technologies often require specific wavelength high-reflectivity structures, high thermal conductivity materials, or water-cooling designs, thus limiting the system's versatility and integration flexibility. In addition, the limited operating wavelength and the "computational holography-external drive" mode result in system complexity, limited response speed, and fragile modal coordination.

[0006] While metasurfaces offer advantages in miniaturization and high integration, their complex design and fabrication processes, sensitivity to fabrication errors, and high costs make them challenging to achieve scalable multi-node collaborative structured light output in engineering scenarios requiring wide wavelengths, high stability, or high power. Furthermore, they face the challenge of high-power laser damage. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a multi-node structured light field generation device with interactive network characteristics that is compact, has no moving parts, has good environmental stability and a high laser damage threshold.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a multi-node structured light field generation device with interactive network characteristics, comprising a transparent substrate and a plurality of diffraction modulation units disposed on the transparent substrate, wherein the diffraction modulation units are sheet-like fork-shaped gratings, and the number of sheet-like fork-shaped gratings is at least three. The sheet-like fork-shaped gratings are integrated and etched on the surface of the transparent substrate by laser direct writing technology. Each sheet-like fork-shaped grating has an independent light field phase modulation function. Starting from the first etched sheet-like fork-shaped grating, from bottom to top, each sheet-like fork-shaped grating rotates in the same direction about a coaxial axis relative to the adjacent sheet-like fork-shaped grating below it to generate a constant misalignment angle. The misalignment angle refers to the relative rotation angle between two adjacent sheet-like fork-shaped gratings. The product of the number of sheet-like fork-shaped gratings and the misalignment angle is less than or equal to 360°.

[0009] Compared with existing technologies, the advantages of this invention are that it overcomes the shortcomings of existing technologies in terms of flexibility, integration, stability, or controllability. It provides a multi-node structured light field generation device with interactive network characteristics based on the core physical dimension of "structural symmetry". In the design, "structural symmetry" is established as a core design factor on par with traditional phase and amplitude, which can realize complex multi-node structured light fields with interactive network characteristics in high-dimensional parameter space, greatly enriching the types and complexity of light fields that can be generated. Moreover, the integrated generation device is a monolithic element with a compact structure and no moving parts, resulting in good environmental stability. This device has a high laser damage threshold and can withstand continuous laser irradiation of up to 200mW. When the spot diameter is 100 micrometers, the optical power density reaches 2546W / cm², and it can cover a wide band from visible light to mid-infrared by material selection, such as chalcogenide glass.

[0010] This invention has broad application prospects. The generated structured light field has a highly customized topological network, which can be immediately applied to fields such as high-dimensional optical information encoding, orbital angular momentum / modulus multiplexing communication, programmable optical tweezers, quantum state preparation and high-capacity optical storage. When applied to the production lines of key components such as power batteries, precision motors and integrated die-cast parts for automobile bodies, it can greatly enrich the information detected and improve the accuracy of detection.

[0011] In one feasible implementation, the number of the sheet-like fork-shaped gratings is 3, and the misalignment angle can be 120° or 60°.

[0012] In one feasible implementation, the optical field phase modulation function is defined by the topological charge value.

[0013] In one feasible implementation, the transparent substrate is made of chalcogenide glass.

[0014] In one feasible implementation, the laser used in the laser direct writing technology is a femtosecond laser with a center wavelength of 1030 nm, a pulse width of 217 fs, and a power of 60.1 nJ to 61.2 nJ. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the three sheet-like fork-shaped gratings and the integrated C3 symmetrical configuration combination in Example 1 of the present invention;

[0016] Figure 2 This is a schematic diagram of the C3 rotationally symmetric configuration combination in Example 1 of the present invention;

[0017] Figure 3 This is a schematic diagram of an optical field network node in Example 1 of the present invention;

[0018] Figure 4 These are far-field diffraction experiment images of all topological charge combinations achieved by the C3 rotationally symmetric configuration combination in Example 1 of this invention.

[0019] Figure 5 This is a schematic diagram of the structure of the combination of three sheet-like fork-shaped gratings and the integrated C6 rotationally symmetric broken configuration in Example 2 of the present invention;

[0020] Figure 6 This is a schematic diagram of the C6 symmetry-breaking configuration combination in Example 2 of the present invention;

[0021] Figure 7 This is a schematic diagram of an optical field network node in Example 2 of the present invention;

[0022] Figure 8These are far-field diffraction experiment images of all topological charge combinations achieved by the C6 symmetry-broken configuration combination in Example 2 of this invention.

[0023] Figure 9 This is a schematic diagram of the structure of the four sheet-like fork-shaped gratings and the integrated C4 rotationally symmetric configuration combination in Example 3 of the present invention;

[0024] Figure 10 This is a schematic diagram of the C4 rotationally symmetric configuration combination in Example 3 of the present invention;

[0025] Figure 11 These are far-field diffraction simulation results of two sets of topological charge combinations implemented using the C4 rotationally symmetric configuration in Example 3 of this invention.

[0026] Figure 12 The images show the far-field diffraction results of two combinations of topological charge values ​​achieved by the C4 rotationally symmetric configuration in Example 3 of this invention. Detailed Implementation

[0027] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present invention and not to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the invention.

[0028] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0029] To address the problems of existing technologies, this embodiment provides a multi-node structured light field generation device with interactive network characteristics, including a transparent substrate and multiple diffraction modulation units disposed on the transparent substrate. The diffraction modulation units are sheet-like fork-shaped gratings, and the number of sheet-like fork-shaped gratings is at least three. The sheet-like fork-shaped gratings are integrated and etched on the surface of the transparent substrate using laser direct writing technology. Each sheet-like fork-shaped grating has an independent light field phase modulation function. Starting from the first etched sheet-like fork-shaped grating, from bottom to top, each sheet-like fork-shaped grating rotates in the same direction about the same axis relative to the adjacent sheet-like fork-shaped grating below it, generating a constant misalignment angle. The misalignment angle refers to the relative rotation angle between two adjacent sheet-like fork-shaped gratings. The product of the number of sheet-like fork-shaped gratings and the misalignment angle is less than or equal to 360°.

[0030] In one embodiment, the number of sheet-like fork gratings is 3, and the misalignment angle is 120° or 60°.

[0031] In one embodiment, the optical field phase modulation function is defined by the topological charge value.

[0032] In one embodiment, the transparent substrate is made of chalcogenide glass.

[0033] In one embodiment, the laser used in the laser direct writing technology is a femtosecond laser with a center wavelength of 1030 nm, a pulse width of 217 fs, and a power of 60.1 nJ to 61.2 nJ.

[0034] The working principle of this invention is as follows: After the incident light is modulated by multiple sheet-like fork-shaped gratings, it will excite multiple discrete diffraction channels. Taking three sheet-like fork-shaped gratings as an example, under the condition of only retaining the approximate 0th order and ±1st order diffraction dominated by each layer, 27 diffraction channels are formed as a whole; each diffraction channel corresponds to a different combination of spatial frequencies, thus mapping into multiple spatially separated energy nodes in the far field or Fourier surface. Furthermore, when the relative spatial orientation of each sheet-like fork-shaped grating satisfies the preset overall structural symmetry, the structural symmetry will act directly on the angular arrangement of the diffraction channels as a global geometric constraint, and induce directional degeneracy: several channels coincide and coherently superimpose in a few specific orientations, so that the energy is stably converged from the dispersed state to several determined node directions, forming a repeatable node skeleton, thereby constituting an optical field network containing multiple spatially separated nodes.

[0035] This invention overcomes the shortcomings of existing technologies in terms of flexibility, integration, stability, and controllability. It provides a device for generating multi-node structured light fields with interactive network characteristics based on the core physical dimension of "structural symmetry." In its design, "structural symmetry" is established as a core design factor alongside traditional phase and amplitude. By setting the misalignment angle between adjacent sheet-like fork-shaped gratings, the symmetry of the overall structure is defined as a global geometric constraint, directly determining the angular arrangement and directionality of the far-field diffraction channels. This determines the node skeleton of the far-field light field topology network, including the number, orientation, and symmetrical distribution of nodes. This enables the realization of complex multi-node structured light fields with interactive network characteristics in a high-dimensional parameter space, greatly enriching the types and complexity of generateable structured light fields. Furthermore, through integration, the device is configured as a single-piece element, resulting in a compact structure with no moving parts and good environmental stability. The multi-node structured light field generation device with interactive network characteristics of the present invention has a high laser damage threshold and can withstand continuous laser irradiation of up to 200mW. When the spot diameter is 100 micrometers, the light power density is as high as 2546W / cm², and it can cover a wide band from visible light to mid-infrared by material selection (such as chalcogenide glass).

[0036] The light field generated by the embodiments of the present invention has a highly customized topological network, which can be immediately applied to fields such as high-dimensional optical information encoding, orbital angular momentum / modulus multiplexing communication, programmable optical tweezers, quantum state preparation and high-capacity optical storage. When applied to the production lines of key components such as power batteries, precision motors and integrated die-cast parts for automobile bodies, it can greatly enrich the information detected and improve the accuracy of detection, with broad application prospects.

[0037] The following examples illustrate the multi-node structured light field generation device with interactive network characteristics provided in the embodiments of the present invention.

[0038] Example 1: Figure 1 This illustrates the structure of the combination of three sheet-like fork-shaped gratings and an integrated C3 rotationally symmetric configuration provided in Example 1.

[0039] like Figure 1As shown, the C3 rotationally symmetric configuration Ga is formed by integrating three sheet-like fork-shaped gratings G1, G2, and G3 on the surface of a transparent substrate made of chalcogenide glass. It exhibits high transmittance in the mid-infrared band. Femtosecond laser direct writing technology is employed, using a femtosecond laser with a center wavelength of 1030 nm, a pulse width of 217 fs, and a power of 60.1 nJ to 61.2 nJ, focused inside the glass through an objective lens with NA=0.80. A spherical aberration pre-compensation and digital alignment process is used to sequentially write the three sheet-like fork-shaped gratings G1, G2, and G3. The grating period can be designed according to the working wavelength and target diffraction angle, preferably from several micrometers to tens of micrometers. In this embodiment, for a working wavelength of 1550 nm, the grating period is designed to be 16 micrometers to obtain a predetermined diffraction angle, which is beneficial for achieving diffraction order separation and subsequent optical field manipulation, while also considering the feasibility of femtosecond laser direct writing and the alignment accuracy of the multilayer structure. Starting with the first inscribed sheet-like fork-shaped grating G1, adjacent sheet-like fork-shaped gratings G2 and G3, relative to G1 and G3 respectively, rotate counterclockwise around the coaxial axis, generating a constant misalignment angle of 120°, forming a C3 rotationally symmetric structure. The schematic diagram of this structure is shown below. Figure 2 As shown, a rectangular coordinate system is established in the horizontal xy plane perpendicular to the optical axis. The phase singularity (center of the fork) of the first sheet-like fork grating G1 is taken as the origin of the coordinate system. The direction of its phase step line is assumed to be perpendicular to the optical axis. The included angle of the axis is Then the second sheet-like fork-shaped grating G2 rotates 120° counterclockwise in space relative to the first sheet-like fork-shaped grating. = +120°, the third sheet-like fork-shaped grating G3 is rotated 240° counterclockwise in space relative to the first sheet-like fork-shaped grating G1. = +240°. At this point, the misalignment angle between each pair of the three sheet-like fork-shaped gratings G1, G2, and G3 is... The angle is 120°, while the number of sheet-like fork-shaped gratings is 3 and the misalignment angle is... The product of is equal to 360°, presenting a C3 rotationally symmetric configuration combination.

[0040] Experimental verification was performed on the structured light field generation results of the C3 rotationally symmetric configuration combination.

[0041] A 1550nm laser is perpendicularly incident on the multi-node structured light field generator with a C3 rotationally symmetric configuration. The resulting light field network nodes are as follows: Figure 3As shown, since a single sheet-like fork-shaped grating will produce 0th order and multiple diffraction orders such as ±1, ±2, ±3, etc. after diffraction, under the approximate condition of retaining only the dominant 0th order and ±1st order diffraction of each layer, after three sheet-like fork-shaped gratings are stacked in a rotationally symmetric manner, the set of three integers marked next to each optical field network node represents the diffraction order corresponding to the three layers of sheet-like fork-shaped gratings at that optical field network node, and forms a diffraction channel; for example, for the set of data (0, 1, -1), it represents the sheet-like fork-shaped grating G The diffraction order corresponding to 1 is 0, and the sheet-like fork-shaped grating... G The diffraction order corresponding to 2 is 1, and the grating is a sheet-like fork shape. G The diffraction order corresponding to 3 is -1. Figure 3 In the diagram, if three sets of data are marked next to a node in the optical field network, it indicates that under the above approximation conditions, there are three superimposed diffraction channels at that node. Similarly, if two sets of data are marked next to a node in the optical field network, it indicates that there are two superimposed diffraction channels at that node. Concentric rings are used to distinguish the different diffraction orders produced by the C3 rotationally symmetric configuration combination in Example 1. From the inside to the outside, the first ring represents the first-order principal diffraction ring, the second ring represents the second-order diffraction ring, and the third ring represents the third-order diffraction ring.

[0042] Different sheet-like fork gratings have an independent optical field phase modulation function, and each sheet-like fork grating encodes a vortex phase. Figure 4 These are far-field diffraction images of all topological charge combinations achieved by the C3 rotationally symmetric configuration in Example 1. It should be noted that... Figure 4 The experimental results only showed the first-order principal diffraction ring, corresponding to Figure 3 The first-order principal diffraction rings, due to the low diffraction efficiency of higher orders, although weak higher-order diffraction can be observed in the experiment, are not obvious.

[0043] by Figure 4 Taking the image in the first row and first column as an example, its topological load combination is ( l 1 , l 2 , l 3 = (1, 1, 1); The far-field diffraction experiment observed six symmetrically distributed diffraction spots (corresponding to the six nodes of the optical field network) in the far field. Each spot exhibited a clear three-petal flower structure, and the experimental results were completely consistent with the theoretical predictions. Under the C3 rotational symmetry constraint, the "petal number" of the spots at each node in the far field was uniformly equal to the sum of the topological charge values. l 1 + l 2 + l 3=3, proving the strong constraint effect of structural symmetry on the topological characteristics of the optical field, and realizing the uniform control of optical field network nodes. From Figure 4 As can be seen from the images, a small number of differences mainly occur under higher topological charge values. Some patterns show a single dark nucleus, which may be caused by the limited femtosecond laser writing resolution and phase modulation error. For example, one pair of diffraction spots with topological charge value combinations such as (3,1,3) and (3,2,1) shows a single dark nucleus.

[0044] Example 2: Figure 5 This illustrates the structure of the combination of three sheet-like fork-shaped gratings and an integrated, inscribed C6 rotationally symmetric broken configuration provided in Example 2. Figure 1 The similarities between Example 1 and Example 2 are that both use chalcogenide glass as the transparent substrate, and the number and structure of the single sheet-like fork gratings are the same, as are the fabrication processes. The difference lies in the misalignment angle: the misalignment angle is 60°, and the product of the number of sheet-like fork gratings (3) and the misalignment angle is 180°, which is less than 360°. Figure 5 label in Gb It represents three sheet-like fork-shaped gratings G 1. G 2 and G 3. Integrated writing of C6 rotationally symmetric broken configuration combinations. For example... Figure 6 As shown, this configuration combination retains C6 symmetry elements locally, but forms a C6 rotationally broken configuration combination globally.

[0045] Experimental verification was performed on the structured light field generation results of the C6 rotationally symmetric broken configuration combination.

[0046] A multi-node structured light field generation device using a 1550nm laser perpendicularly incident on this C6 rotationally symmetric broken configuration combination achieves a light field network node such as... Figure 7 As shown, Figure 7 The meaning of the data labeled next to the concentric rings and nodes Figure 3 Consistent.

[0047] Figure 8 These are far-field diffraction experimental images of all topological charge combinations achieved by the C6 rotationally broken configuration combination in Example 2, corresponding to... Figure 7 The first-order principal diffraction rings were observed. Weak higher-order diffraction could also be observed during the experiment, but it was not significant.

[0048] by Figure 8 Taking the image in the first row and second column as an example, its topological load combination is ( l 1 , l 2 , l 3= (1, 1, 2). In the observed far-field diffraction results, six principal diffraction spots were also formed in the far field, but their topological structures exhibited significant anisotropy. Specifically, the six spots displayed various morphologies, including a double-petaled flower structure, a vortex spot with two singularities, and a vortex spot with a single singularity. From... Figure 8 As can be seen, the characteristics of this complex "interactive network" are highly consistent with the results based on the theoretical model of this invention. This second example demonstrates that by purposefully designing the structural symmetry dimension of "symmetry breaking," a richer degree of control freedom can be unlocked, thereby generating light spots with multiple topological forms in parallel within an optical field network, achieving differentiated and complex control of the optical field network.

[0049] Example 3: Figure 9 This example illustrates the structure of the combination of four sheet-like fork-shaped gratings and an integrated C4 rotationally symmetric configuration provided in Example 3. Figure 1 The similarities between Example 1 and Example 2 are that both use chalcogenide glass as the transparent substrate, have the same individual sheet-like fork-shaped grating structure, and are manufactured using the same process. The difference lies in the number of sheet-like fork-shaped gratings: four (…). G 1. G 2. G 3 and G 4) Figure 9 label in Gc It represents four sheet-like fork-shaped gratings G 1. G 2. G 3 and G 4. Integrated C4 rotationally symmetric configuration combination. For example... Figure 10 As shown, the misalignment angle is 90°, and the product of the number of sheet-like fork gratings 4 and the misalignment angle is equal to 360°, presenting a C4 rotationally symmetric configuration.

[0050] Figure 11 The figure shows the simulation results of far-field diffraction for two combinations of topological charge values ​​achieved by the C4 rotationally symmetric configuration in Example 3. The topological charge value combination in the left figure is ( l 1 , l 2 , l 3 , l 4) = (1, 1, 1, 1), the topological load combination in the right figure is ( l 1 , l 2 , l 3 , l 4) = (2, 2, 2, 2).

[0051] Figure 12The figure shows the far-field diffraction results of two combinations of topological charge values ​​achieved by the C4 rotationally symmetric configuration in Example 3. The topological charge value combination in the left figure is ( l 1 , l 2 , l 3 , l 4) = (1, 1, 1, 1), the topological load combination in the right figure is ( l 1 , l 2 , l 3 , l 4) = (2, 2, 2, 2), topological load combination and Figure 11 same.

[0052] In some embodiments, the number of sheet-like fork-shaped gratings can be set to n , n It is a positive integer greater than or equal to 3; when n When the individual sheet-like fork-shaped gratings are distributed at equal angular intervals, the overall grating assembly forms a structure with C. n The structure of a combination of rotationally symmetric configurations. For example, it can be expressed by the following formula: the first... The rotation angle of the sheet-like fork-shaped grating satisfies: ,in It is an offset angle. This equiangular spacing configuration enables each diffraction channel to be evenly arranged in the angular direction, thereby forming a regular equiangularly spaced multi-node structured light field in the far field.

[0053] Furthermore, based on the aforementioned equal-angle interval configuration, if a controlled deviation is applied to at least one adjacent inter-story misalignment angle (i.e.... No longer equal to If the rotational symmetry of the overall grating assembly is reduced or broken, the originally equivalent far-field nodes will have distinguishable differentiated outputs (e.g., different petal numbers, dark nucleus morphology, and other characterization parameters at different nodes), thereby improving the addressability and controllability of the nodes.

[0054] For example: when =3 and orientation satisfies When the C3 rotationally symmetric configuration is combined, a structured light field with regularly arranged channels can be obtained;

[0055] when =4 and the difference between adjacent orientation angles is At this time, it presents a C4 rotationally symmetric configuration combination with a misalignment angle of 90°;

[0056] when =5 and the difference between adjacent orientation angles is At that time, it presents a C5 rotationally symmetric configuration combination with an offset angle of 72°;

[0057] when =6 and the difference between adjacent orientation angles is At that time, it presents a C6 rotationally symmetric configuration combination with a misalignment angle of 60°.

[0058] In some three-piece ( n In the embodiment where =3), the misalignment angle between adjacent layers can also be used. The non-equiangular spacing configuration (C6 symmetry broken configuration combination) means that the angle between the first two of the three sheet-like fork gratings is 60°, and the angle between the third and the first does not meet the 60° requirement. At this time, the grating combination no longer satisfies the C3 equiangular symmetry constraint, but a node skeleton with a six-vertex distribution characteristic can still be formed in the far field. Due to the reduced symmetry, each node can exhibit different local morphologies, thereby achieving differentiated and addressable node output.

[0059] In the embodiments of this application, n The scheme with a value of 3 achieves a good balance between structural complexity, sensitivity to manufacturing errors, and far-field stability; when n As the size increases further, the requirements for machining accuracy also increase accordingly.

[0060] The experimental results for the laser damage threshold are as follows: For the C3 rotationally symmetric configuration combination in Example 1, the power with the clearest diffraction pattern was selected for measurement. When only a continuous laser with a power of 10mW was used for irradiation, the calculated optical power density reached 127W / cm² when the spot size was 100 micrometers, which greatly exceeded the 10W / cm² of the prior art. When the power of the continuous laser reached the highest of 200mW, the calculated optical power density was as high as 2546W / cm² when the spot diameter was 100 micrometers.

[0061] For the fabrication of sheet-like fork-shaped gratings, the femtosecond laser direct writing processing parameters can be optimized based on the material, target diffraction efficiency, and mode purity as follows:

[0062] Laser pulse energy: The maximum pulse energy of a laser system with an optimal power window (approximately 60.1 nJ to 61.2 nJ). Too low a pulse energy will result in incomplete structural inscription, while too high a pulse energy will cause nonlinear damage to the material.

[0063] Grating groove depth (modulation depth): There is an optimal range (approximately 3-4 micrometers). If it is too shallow, it will lead to insufficient phase modulation; if it is too deep, it will introduce excessive scattering loss.

[0064] Duty cycle: A balance needs to be struck between diffraction efficiency and mode purity. Experiments show that a duty cycle in the range of 0.5 to 0.6 can achieve better diffraction efficiency while maintaining high mode purity.

[0065] Scanning strategy: With optimized pulse energy, single-layer scanning can usually achieve better mode purity than multi-layer scanning, avoiding structural distortion caused by heat accumulation.

Claims

1. An apparatus for generating a multi-node structured light field having an interactive network property, comprising a transparent substrate and a plurality of diffractive modulation units disposed on the transparent substrate, characterized in that, The diffraction modulation unit is a sheet-like fork-shaped grating, and the number of the sheet-like fork-shaped gratings is at least three. The sheet-like fork-shaped gratings are integrated and etched on the surface of the transparent substrate using laser direct writing technology. Each sheet-like fork-shaped grating has an independent optical field phase modulation function. Starting from the first etched sheet-like fork-shaped grating, from bottom to top, each sheet-like fork-shaped grating rotates in the same direction about the same axis relative to the adjacent sheet-like fork-shaped grating below it, generating a constant misalignment angle. The misalignment angle refers to the relative rotation angle between two adjacent sheet-like fork-shaped gratings. The product of the number of sheet-like fork-shaped gratings and the misalignment angle is less than or equal to 360°.

2. The apparatus for generating a multi-node structured light field with interactive network characteristics of claim 1, wherein, The number of the sheet-like fork-shaped gratings is 3.

3. The apparatus for generating a multi-node structured light field with interactive network characteristics of claim 2, wherein, The misalignment angle is 120°.

4. The apparatus for generating a multi-node structured light field with interactive network characteristics of claim 2, wherein, The misalignment angle is 60°.

5. The apparatus for generating a multi-node structured light field with interactive network characteristics of claim 1, wherein, The optical field phase modulation function is defined by its topological charge value.

6. The apparatus of claim 1, wherein the multi-node structured light field with interactive network characteristics is generated by: The transparent substrate is made of chalcogenide glass.

7. The device for generating a multi-node structured light field with interactive network characteristics as described in claim 1, characterized in that, The laser used in the laser direct writing technology is a femtosecond laser with a center wavelength of 1030nm, a pulse width of 217fs, and a power of 60.1nJ~61.2nJ.

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