A grating encoder and encoding method

Abstract

The embodiment of the present application provides a grating encoder and an encoding method, and relates to the technical field of integrated optical devices. The grating encoder comprises an optical signal input end, a mode regulation area and an optical signal output end, the mode regulation area comprises a substrate, at least two straight waveguides and at least one subwavelength grating waveguide; the at least two straight waveguides and the at least one subwavelength grating waveguide are alternately and equally spaced arranged on the substrate; the duty cycle of one subwavelength grating waveguide in the unit where the subwavelength grating waveguide is located is 0.5, and the unit is composed of the subwavelength grating waveguide, the straight waveguide alternately arranged with the subwavelength grating waveguide and the interval between the subwavelength grating waveguide and the straight waveguide; one subwavelength grating waveguide and one straight waveguide alternately arranged with the subwavelength grating waveguide jointly constitute one unit cell, and each individual unit cell contains one normalized flux. The signal strength attenuation and mode distortion are reduced.

Description

Technical Field

[0001] This invention relates to the field of integrated optical device technology, and in particular to a grating encoder and encoding method. Background Technology

[0002] Grating encoders are a type of passive optical device that uses periodic gratings to convert incident light fields into multiple binary or multi-level grayscale symbols. They are widely used in on-chip optical computing, parallel data processing, high-speed optical interconnects, precision sensing, and quantum information processing.

[0003] Currently, traditional grating encoders mainly include two structures: straight waveguide encoders and large-period grating encoders. These two types of encoders have obvious technical defects in practical applications: on the one hand, due to large scattering and diffraction losses, they are prone to signal strength reduction and mode distortion; on the other hand, their grating period is usually much larger than the operating wavelength, and the light will generate multi-order diffraction and severe scattering loss during propagation, resulting in signal strength attenuation and mode distortion. Summary of the Invention

[0004] The purpose of this invention is to provide a grating encoder and encoding method to reduce signal strength attenuation and mode distortion. The specific technical solution is as follows:

[0005] In a first aspect, a grating encoder is provided, comprising:

[0006] The optical signal input terminal, the mode control area, and the optical signal output terminal are provided. The optical signal input from the optical signal input terminal passes through the mode control area and is output from the optical signal output terminal.

[0007] The mode control region includes: a substrate, at least two straight waveguides and at least one subwavelength grating waveguide;

[0008] At least two straight waveguides and at least one subwavelength grating waveguide are arranged alternately and at equal intervals on the substrate;

[0009] A subwavelength grating waveguide has a duty cycle of 0.5 in its own unit, which is composed of the subwavelength grating waveguide, straight waveguides arranged alternately with the subwavelength grating waveguide, and the interval between them;

[0010] A subwavelength grating waveguide and a straight waveguide alternating with the subwavelength grating waveguide together form a unit cell, each unit cell containing a normal flux. .

[0011] Optionally, a straight waveguide arranged in front and a subwavelength grating waveguide arranged behind the straight waveguide form a unit cell.

[0012] Optionally, the waveguides arranged alternately and at equal intervals begin with a straight waveguide and end with a straight waveguide.

[0013] Optionally, the period of the subwavelength grating waveguide is 0.3 μm.

[0014] Optionally, the spacing between a straight waveguide and an adjacent subwavelength grating waveguide can range from 180 to 380 nm.

[0015] Optionally, the spacing between a straight waveguide and an adjacent subwavelength grating waveguide is 280 nm.

[0016] Optionally, at least two straight waveguides and at least one subwavelength grating waveguide have a length of 20 μm in the waveguide propagation direction, the width of the subwavelength grating waveguide is 0.6 μm, and the width of the straight waveguide is 114 nm.

[0017] Optionally, the height of at least two straight waveguides and at least one subwavelength grating waveguide is 0.6 μm.

[0018] Optionally, the substrate is made of silicon dioxide, and the at least two straight waveguides and at least one subwavelength grating waveguide are made of silicon.

[0019] Secondly, an encoding method is provided, including:

[0020] At the optical signal output end of the grating encoder, the light intensity of each waveguide in the mode control region of the grating encoder is collected, wherein the grating encoder is the grating encoder described in any of the first aspects above.

[0021] The collected light intensity is compared with a preset threshold, and the encoded value is obtained based on the comparison result.

[0022] Beneficial effects of the embodiments of the present invention:

[0023] In this embodiment of the invention, in the mode control region of the grating encoder, at least two straight waveguides and at least one subwavelength grating waveguide are alternately and equally spaced on the substrate. The duty cycle of a subwavelength grating waveguide in its own unit cell is 0.5. The unit cell is composed of a subwavelength grating waveguide, straight waveguides alternating with the subwavelength grating waveguide, and the spacing between them. A subwavelength grating waveguide and a straight waveguide alternating with the subwavelength grating waveguide together form a unit cell. Each individual unit cell contains one normalized flux. The π-gauge flux causes the optical path interference within the unit cell to cancel each other out, forming the AB trapping effect, which localizes the light to a single unit cell, enabling diffraction-free compact local transmission of the encoder, thereby reducing signal strength attenuation and mode distortion.

[0024] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0026] Figure 1 This is a schematic diagram of the structure of a grating encoder provided in an embodiment of the present invention;

[0027] Figure 2 for Figure 1 Schematic diagram of the structure of the control zone in the medium-mode model;

[0028] Figure 3 This is a schematic diagram of the equivalent lattice structure obtained by the alternating subwavelength grating waveguides and straight waveguides in an embodiment of the present invention.

[0029] Figure 4 for Figure 2 The front view;

[0030] Figure 5 This is a schematic diagram of the refractive index under different duty cycles in an embodiment of the present invention;

[0031] Figure 6 This is an equivalent schematic diagram of the tightly bound model of the unit cell in an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram of the theoretical and simulated band structure when g = 280 nm in an embodiment of the present invention;

[0033] Figure 8 This is a schematic diagram illustrating the changes in the band structure under different gaps g in an embodiment of the present invention;

[0034] Figure 9 This is a schematic diagram of the simulated optical field evolution under three different gap distances of g=180 nm, 280 nm and 380 nm in an embodiment of the present invention;

[0035] Figure 10 A flowchart of the encoding method provided in the embodiments of the present invention;

[0036] Figure 11 This is a schematic diagram illustrating the optical mode encoding effect when implementing a single waveguide input in an embodiment of the present invention;

[0037] Figure 12This is a schematic diagram illustrating the optical mode encoding effect when implementing dual waveguide input in an embodiment of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art based on the present invention are within the scope of protection of the present invention.

[0039] like Figure 1 As shown, the grating encoder provided in this embodiment of the invention may include:

[0040] The optical signal input terminal 11, the mode control area 12, and the optical signal output terminal 13 are provided. The optical signal input from the optical signal input terminal 11 passes through the mode control area 12 and is output from the optical signal output terminal 13.

[0041] like Figure 2 As shown, the mode control region 12 includes: a substrate 21, at least two straight waveguides 22 and at least one subwavelength grating waveguide 23;

[0042] At least two straight waveguides 22 and at least one subwavelength grating waveguide 23 are arranged alternately and at equal intervals on the substrate;

[0043] A subwavelength grating waveguide has a duty cycle of 0.5 in its own unit cell. The unit cell consists of subwavelength grating waveguides, straight waveguides that alternate with subwavelength grating waveguides, and the gaps between them.

[0044] A subwavelength grating waveguide and a straight waveguide alternating with it together form a unit cell, each unit cell containing a gauge flux. .

[0045] Here, "alternation" refers to the alternation of straight waveguides and subwavelength grating waveguides. For example, straight waveguide, subwavelength grating waveguide, straight waveguide, subwavelength grating waveguide... arranged in sequence.

[0046] In this embodiment of the invention, the waveguides are arranged alternately and at equal intervals, starting with a straight waveguide. The first straight waveguide and the next subwavelength grating waveguide form a unit cell, and the last straight waveguide is a separate unit.

[0047] This can also be understood as each waveguide starting with a straight waveguide and ending with a straight waveguide. Furthermore, straight waveguides and subwavelength gratings are arranged alternately at equal intervals, and each unit cell contains one straight waveguide and one subwavelength grating. The last straight waveguide is a separate unit cell.

[0048] Equally spaced arrangement refers to alternating straight waveguides and subwavelength grating waveguides, with intervals between subwavelength grating waveguides and straight waveguides, and the intervals between each straight waveguide and the alternating subwavelength grating waveguides, as well as between each subwavelength grating waveguide and the alternating straight waveguides, are all equal.

[0049] In this embodiment of the invention, in the mode control region of the grating encoder, at least two straight waveguides and at least one subwavelength grating waveguide are alternately and equally spaced on the substrate. The duty cycle of a subwavelength grating waveguide in its own unit cell is 0.5. The unit cell is composed of a subwavelength grating waveguide, straight waveguides alternating with the subwavelength grating waveguide, and the spacing between them. A subwavelength grating waveguide and a straight waveguide alternating with the subwavelength grating waveguide together form a unit cell. Each individual unit cell contains one normalized flux. The π-gauge flux causes the optical path interference within the unit cell to cancel each other out, forming the AB trapping effect, which localizes the light to a single unit cell, enabling diffraction-free compact local transmission of the encoder, thereby reducing signal strength attenuation and mode distortion.

[0050] In the composite structure of subwavelength grating waveguide and straight waveguide, the normal flux is introduced by equivalent means. The grating encoder provided in this embodiment of the invention can be understood as a diffraction-free encoder, which achieves mode matching so that the fundamental mode of the straight waveguide can gradually transition to the equivalent mode of SWG (Subwavelength Grating, SWG).

[0051] Furthermore, by utilizing the π gauge field to induce flat-band diffraction-free compact local modes, the mode coupling efficiency of the optical encoder is effectively improved, multi-order diffraction and scattering losses are significantly reduced, and structural robustness is enhanced, making it suitable for fields such as on-chip optical computing, high-speed optical interconnects, and quantum information processing.

[0052] The spacing between each subwavelength grating waveguide and straight waveguide is uniform. By setting the structural duty cycle of the subwavelength grating waveguide and straight waveguide, the subwavelength grating structure was simulated in the weak form module of simulation software such as COMSOL (a multiphysics simulation software), and it was found that two modes are supported in the subwavelength grating. Figure 3 The equivalent lattice structure derived from alternating subwavelength grating waveguides and straight waveguides can also be understood as an AB-trapped lattice based on an artificial gauge field. For example... Figure 3 As shown, the equivalent lattice structure derived from the alternating subwavelength grating waveguides and straight waveguides is similar to a rhombic chain lattice, where each subwavelength grating waveguide and straight waveguide together form a unit cell, and each individual unit cell contains a gauge flux. .

[0053] Based on the coupled mode equations, the equations in the coupling process can be determined as follows:

[0054]

[0055]

[0056]

[0057] in, This represents the field amplitude of the fundamental mode of the straight waveguide corresponding to the nth element. , This represents the field amplitude of the higher-order mode of the subwavelength grating corresponding to the nth element. The refractive indices of the straight waveguide fundamental mode and the higher-order mode of the subwavelength grating are equal, where n represents the number of elements and t = 0.184 μm. -1 It is the coupling coefficient. Since each unit cell contains π gauge flux, we take... π flux causes destructive interference of optical paths within the unit cell (such as coupling path a). n →a n+1 The phase difference is π, forming the AB trapping effect, which localizes the light to a single unit cell.

[0058] Represents the field amplitude of the mode corresponding to the (n+1)th element. The field amplitude of the mode corresponding to the (n-1)th unit The field amplitude of the mode corresponding to the (n-1)th element.

[0059] If light is incident in the fundamental mode, according to Bloch's theorem, that is... Where a, b, and c are the amplitudes of the Bloch mode, and k is the horizontal momentum. x The x-component represents the wave vector (crystal momentum). This refers to the energy of the fundamental mode of a straight waveguide. , This refers to the energy of the higher-order modes of the subwavelength grating. This can be derived from the preceding equations:

[0060]

[0061]

[0062]

[0063] Extending it to matrix form, we can obtain its Hamiltonian:

[0064]

[0065] It can be observed that the diagonal data of these three Hamiltonians are all zero. To facilitate the diagonalization of the Hamiltonians, only the nearest neighbor coupling term is considered, ignoring the second nearest neighbor coupling. Then, by finding the eigenvalues ​​and eigenvectors of the Hamiltonian matrix, the three eigenvalues ​​of E will be obtained. It can be observed that the value of E includes t but not momentum, which indicates that the eigenvalues ​​of the system composed of subwavelength grating waveguides and straight waveguides are independent of Bloch momentum, and the corresponding eigenvectors ( Corresponding feature quantity , Corresponding feature quantity , Corresponding feature quantity ) can be represented as:

[0066]

[0067]

[0068]

[0069] Using eigenstates, the topological invariants of the system can be calculated using a volume model of periodic boundary conditions, and the occurrence of topological boundary states in the lattice points can be predicted based on the calculation results.

[0070] In this embodiment of the invention, a canonical flux is introduced into each SWG cell. This is used to excite flat-band diffraction-free compact local modes, achieving efficient coupling and conversion of optical modes, thereby completing the binary encoding function of optical signals.

[0071] Since each unit cell contains π gauge flux, we take , where t = 0.0398 μm -1 It is the coupling coefficient. The π gauge flux causes destructive interference of optical paths within the unit cell (such as coupling paths). → The phase difference is π, forming an AB trapping effect that localizes light to a single unit cell. Flat-band diffraction-free modes maintain energy localization between adjacent units and are independent of Bloch momentum, enabling robust transmission under structural size changes or disordered perturbations.

[0072] In this embodiment of the invention, the length of at least two straight waveguides and at least one subwavelength grating waveguide in the waveguide propagation direction is 20 μm, the width of the subwavelength grating waveguide is 0.6 μm, the width of the straight waveguide is 114 nm, and the height of at least two straight waveguides and at least one subwavelength grating waveguide is 0.6 μm.

[0073] Among them, such as Figure 2As shown, the z-axis represents the waveguide propagation direction, and the length of the straight waveguide and the subwavelength grating waveguide in the waveguide propagation direction is the length of the waveguide in the z-axis direction.

[0074] like Figure 4 As shown, from the x-direction (lateral spatial position) and y-direction (vertical spatial position), g represents the spacing between the straight waveguide and the adjacent subwavelength grating waveguide, W1 represents the width of the subwavelength grating waveguide, W2 represents the width of the straight waveguide, and h represents the height of the straight waveguide and the subwavelength grating waveguide.

[0075] The substrate is made of silicon dioxide, and at least two straight waveguides and at least one subwavelength grating waveguide are made of silicon.

[0076] In the mode control region of the grating encoder provided in this embodiment of the invention, at least two straight waveguides and at least one subwavelength grating waveguide are alternately and equally spaced on the substrate. That is, by alternately setting subwavelength grating waveguides and straight waveguides on an insulator silicon platform, precise control of mode phase and diffraction effects is achieved using the subwavelength grating waveguides, while the straight waveguides provide a low-loss multi-mode guidance channel, thus fabricating an optical encoder and realizing effective mode control and binary encoding functions. Furthermore, in the composite structure of subwavelength grating waveguides and straight waveguides, equivalent normalized flux is introduced. To achieve diffraction-free compact local transmission, the grating encoder provided in this embodiment can be understood as a diffraction-free encoder. It can be understood that the encoder provided in this embodiment is a diffraction-free encoder based on a subwavelength grating flat-band design.

[0077] In addition, to alleviate the energy redundancy caused by multi-order diffraction, traditional solutions often require longer propagation lengths or additional coupling segments, which increases the device size and restricts its application on high-density photonic integration platforms.

[0078] This invention incorporates a subwavelength grating waveguide. Subwavelength grating waveguide technology, by reducing the grating period to the subwavelength level, enables precise control of optical field dispersion and distribution, significantly improving coupling efficiency and bandwidth. Furthermore, this invention, combined with flat-band topology design, effectively introduces π-gauge flux into the photonic lattice, exciting completely diffraction-free compact localized modes. This allows light energy to be spontaneously confined within the unit cell without diffusion due to Bloch momentum, achieving diffraction-free stable transmission. It possesses advantages such as no size limitations, strong disorder robustness, and topological boundary state stability, making it suitable for on-chip optical computing, parallel data processing, high-speed optical interconnects, and quantum information processing. Strong disorder robustness can also be understood as achieving robust transmission under structural size variations or disordered perturbations, which can include variations in wavelength, different numbers of lattice points, and different spacing.

[0079] In one embodiment, straight waveguides and subwavelength grating waveguides are arranged alternately and at equal intervals on a substrate. The substrate is made of silicon dioxide, and both the straight waveguides and subwavelength grating waveguides are made of silicon. The length of the waveguide in the waveguide propagation direction is set to L = 20 μm, the interval between the straight waveguide and the subwavelength grating waveguide is g = 280 nm, the width of the subwavelength grating waveguide is W1 = 0.6 μm, the grating period is Λ = 0.3 μm, the duty cycle is f = 0.5, the width of the straight waveguide is W2 = 114 nm, and the height of both is h = 0.6 μm.

[0080] The spacing between each subwavelength grating waveguide and straight waveguide is uniform. By setting the structural duty cycle of the subwavelength grating waveguide and straight waveguide, the subwavelength grating structure was simulated in the weak form module of the simulation software. It was found that the subwavelength grating supports two modes, in which each subwavelength grating waveguide and straight waveguide together form a unit cell, and each individual unit cell contains a gauge flux. Since each unit cell contains the gauge flux of π, we take... , where t = 0.0398 μm -1 It is the coupling coefficient. The π flux causes destructive interference of the optical path within the unit cell, resulting in the AB trapping effect, which localizes the light to a single unit cell. The equivalent lattice structure derived from alternating subwavelength grating waveguides and straight waveguides is as follows: Figure 3 As shown.

[0081] Flat-band topology design, by effectively introducing π-gauge flux into the photonic lattice, can excite completely diffraction-free compact localized modes, allowing light energy to be spontaneously confined within the cell without diffusion due to Bloch momentum. This provides significant resistance to structural size variations and manufacturing errors, offering a new approach for achieving efficient and stable miniaturized encoders. Furthermore, in this embodiment, the flat-band compact localization effect induced by the π-gauge field is combined with an SWG / straight waveguide composite structure for optical encoding. This achieves miniaturized, highly integrated, and high-precision optical encoding while improving mode coupling efficiency, suppressing scattering loss, and enhancing structural robustness. The grating encoder provided in this embodiment is a novel grating encoder based on π-gauge flux-induced flat-band compact localized modes.

[0082] In this embodiment of the invention, a subwavelength grating waveguide has a duty cycle of 0.5 within its own unit cell. The unit cell consists of subwavelength grating waveguides, straight waveguides alternating with subwavelength grating waveguides, and the spacing between them. The period of a subwavelength grating waveguide is 0.3 μm. Wherein, as... Figure 2 In the diagram, Λ represents the period of the subwavelength grating waveguide, which is the grating period.

[0083] The duty cycle is 0.5, which makes the effective refractive index of the higher-order modes equal to that of the fundamental mode.

[0084] like Figure 5 As shown, HE in subwavelength gratings at different duty cycles 11 (fundamental mode) and quasi-TE 01 (qausi- TE) 01 The effective refractive index of (higher-order modes), HE 11 Corresponding to line 501, quasi-TE 01 For line 502, HE is at duty cycle f = 0.5. 11 With quasi-TE 01 Modular degeneracy (n eff0 = 1.82), n eff0 That is, n in the diagram eff When the effective refractive index of the subwavelength grating waveguide mode is equal to the effective refractive index of the straight waveguide mode, and both are n... eff0 = 1.82, the two modes can be coupled to form an array for light propagation on the same plate; furthermore, the equivalent schematic diagram of the tight-binding model of a unit cell of this array is as follows Figure 6 As shown, where E y This refers to the energy along the y-axis, or the energy of the y-component of the electric field, which can vary from -1 to 1. It can be understood that when the duty cycle is 0.5, degenerate higher-order modes with different spatial symmetries are formed, such as... Figure 6 The t and -t modes form degenerate higher-order modes with different spatial symmetries. When these modes couple with the fundamental mode of an adjacent straight waveguide, a synthetic π gauge field is generated, which induces a flat band through the AB cage. Further research reveals that this mechanism can form spatially compact, symmetrically protected topological edge states. The synthetic π gauge field induces a flat band through the AB cage, and this structure can reduce the diffusion of the optical field.

[0085] In this embodiment of the invention, the spacing between a straight waveguide and an adjacent subwavelength grating waveguide ranges from 180 to 380 nm.

[0086] Specifically, the spacing between a straight waveguide and an adjacent subwavelength grating waveguide is 280 nm.

[0087] like Figure 7 As shown, the theoretical (line) and simulated (point) band structures at g = 280 nm are as follows: Figure 8 As shown, the band structure changes with different gaps g (nm) for a subwavelength grating waveguide with a period Λ = 0.3 μm and a duty cycle f = 0.5, where k x The x-component represents the wave vector (crystal momentum) and describes the spatial periodicity of the Bloch wave in the x-direction. x / π is kx The dimensionless representation, E / t, represents the ratio of energy to coupling coefficient.

[0088] from Figure 7 It can be observed that the three energy bands are flat at this time, indicating that the subwavelength grating and the straight waveguide mode can be well coupled. At this time, diffraction-free transmission will occur, and the energy will be basically kept in the middle waveguide, making the transmission more stable. Figure 8 The three band structures, from top to bottom, are: (the above) (corresponding feature quantity) (the above) (corresponding feature quantity) (the above) (Corresponding feature quantity). From Figure 8 As can be seen, when the gap g decreases, the coupling coefficient t increases and the band separation occurs (E=±2t), but the band remains flat, indicating that the encoder provided in this embodiment of the invention can still maintain excellent performance under different gaps g.

[0089] Figure 9 The simulated optical field evolution is shown for three different gap distances: g = 180 nm, g = 280 nm, and g = 380 nm. Simulations were performed on four elements (N = 4) of the array using FDTD (Finite Difference Time Domain), where four elements refer to four unit cells. In all cases, the light remains well confined to the initially excited waveguide and adjacent SWG elements throughout propagation, exhibiting negligible diffraction. Here, 0 represents the dark region of the optical field P; 1 represents the bright region of the optical field P; x (μm) represents the lateral spatial position (along the left-right direction of the structure); z (μm) represents the spatial position along the propagation direction / depth, and represents the distance from the incident surface (z = 0).

[0090] In this embodiment of the invention, the π gauge field induces a flat-band diffraction-free compact local mode, which effectively improves the mode coupling efficiency of the optical encoder, significantly reduces multi-order diffraction and scattering losses, and enhances structural robustness. It is suitable for fields such as on-chip optical computing, high-speed optical interconnects, and quantum information processing.

[0091] Meanwhile, the encoder provided in this invention features suppression of multi-order diffraction and scattering losses, efficient mode selection and coupling, inherent robustness to process errors and structural disturbances, and multi-mode, multi-wavelength parallel encoding capabilities. This effectively meets the technical requirements for high precision, high stability, and high integration in fields such as on-chip optical computing, high-speed optical interconnects, and quantum information processing. Specifically, by adjusting grating parameters, degenerate higher-order modes with different spatial symmetries are designed. When these modes couple with the fundamental mode of adjacent straight waveguides, a synthetic π-gauge field is generated, inducing a flat band through an AB cage. This mechanism can form spatially compact, symmetrically protected topological edge states. It can maintain the lateral distribution of the beam during propagation, thus achieving diffraction-free propagation.

[0092] In summary, the embodiments of the present invention have the following advantages and beneficial effects:

[0093] (1) In this embodiment of the invention, by equivalently introducing π-gauge flux inside the SWG unit, a flat-band diffraction-free compact local mode is excited, which significantly improves the mode coupling efficiency, effectively suppresses multi-order diffraction and scattering loss, and enhances the transmission stability of optical signals.

[0094] (2) The composite waveguide structure in the embodiments of the present invention realizes precise mode control and selective transmission at the subwavelength scale, making the device structure more compact and beneficial for application in high-density photonic integrated chips.

[0095] Among them, the subwavelength grating achieves a continuously tunable refractive index distribution through the equivalent medium effect, which can precisely control the propagation constant and mode distribution of light waves. By adjusting the duty cycle, the target mode can be stably transmitted, while undesired modes are effectively suppressed due to cutoff or leakage, thereby achieving low-loss precise mode control and selective transmission.

[0096] (3) The structural design of the present invention has natural robustness to process errors and structural disturbances, which improves the repeatability of device manufacturing and long-term stability.

[0097] (4) The embodiments of the present invention can realize multi-mode, multi-wavelength parallel transmission and encoding by flexibly adjusting the structural parameters of the SWG unit, effectively meeting the technical requirements of on-chip optical computing, high-speed optical interconnect and quantum information processing for functional diversity, high precision and high integration.

[0098] This invention also provides an encoding method, such as... Figure 10 As shown, it includes:

[0099] S1001, at the optical signal output end of the grating encoder, the light intensity of each waveguide in the mode control area of ​​the grating encoder is collected, wherein the grating encoder is the grating encoder in the above embodiment.

[0100] S1002 compares the collected light intensity with a preset threshold and obtains the encoded value based on the comparison result.

[0101] In this embodiment of the invention, in the mode control region of the grating encoder, at least two straight waveguides and at least one subwavelength grating waveguide are alternately and equally spaced on the substrate. The duty cycle of a subwavelength grating waveguide in its own unit cell is 0.5. The unit cell is composed of a subwavelength grating waveguide, straight waveguides alternating with the subwavelength grating waveguide, and the spacing between them. A subwavelength grating waveguide and a straight waveguide alternating with the subwavelength grating waveguide together form a unit cell. Each individual unit cell contains one normalized flux. The π-gauge flux causes destructive interference of the optical path within the unit cell, creating the AB trapping effect. This localizes the light within a single unit cell, enabling diffraction-free, compact local transmission by the encoder, thus reducing signal strength attenuation and mode distortion. Consequently, this grating encoder can improve encoding accuracy.

[0102] In one example, the encoding method of the grating encoder provided in the above embodiments may include:

[0103] Step 1: Introduce the incident light signal at the input end.

[0104] The input terminal is the optical signal input terminal mentioned above.

[0105] Step 2: The incident light signal propagates in the mode control region through the alternating arrangement of SWG units and straight waveguides and optical coupling.

[0106] Step 3: Introduce normalized flux into each SWG cell This enables the excitation and mode selection of flat-band diffraction-free compact local modes.

[0107] Step 4: Collect the light intensity in each output waveguide at the output end and normalize it.

[0108] The output terminal is the optical signal output terminal mentioned above.

[0109] Step 5: Compare the normalized light intensity with the preset threshold γ to determine the binary code value.

[0110] The value of γ can be determined based on actual needs or experience. For example, the value of γ can range from 0.1 to 0.5.

[0111] Step 6: Generate the binary code output of the optical signal based on the judgment result.

[0112] Specifically:

[0113] (1) Alternating and optically coupled subwavelength grating waveguide units and straight waveguide units are fabricated on a silicon-on-insulator (SOI) platform, and equivalent gauge flux is introduced inside the SWG unit. .

[0114] (2) By adjusting the period Λ and duty cycle f of the SWG unit, as well as the spacing g between the straight waveguide and the SWG unit, the excitation and mode coupling efficiency of the flat band diffraction-free compact local mode is optimized.

[0115] (3) The incident light signal is coupled into the alternating structure through the input end, and diffraction-free compact transmission and mode conversion are performed in the mode control region.

[0116] (4) Set up multiple detection channels at the output end, normalize the output light intensity of each channel, and compare the normalized light intensity with the preset threshold γ to determine the binary code value of each channel.

[0117] (5) Combine the binary determination results of each channel in a predetermined order to obtain the required binary optical code output.

[0118] The encoder's structural parameters can be adjusted according to actual application requirements to achieve parallel transmission and encoding functions in multiple modes and wavelengths.

[0119] In one embodiment, according to the design principle of the subwavelength grating diffraction-free encoder provided in the embodiment of the present invention, the encoder duty cycle f = 0.5 and the periodic propagation distance are set to 12.07 μm. Figure 11 In the model with N = 4 (13 waveguide units), a single-channel optical signal is injected into the input end through finite-difference time-domain (FDTD) simulation analysis. The light intensity of each channel at the output end is normalized. A threshold γ = 0.2 is set. The normalized light intensity is judged as "1" if it is higher than γ and as "0" if it is lower than γ, forming an optical binary code. For example: (a) Input [1000000000000], output [1000000000000]; (b) Input [0000001000000], output [1000110110000]; (c) Input [0000000000001], output [0000000000001].

[0120] Further conduct simulations of dual-input modes, in Figure 9 Under the structure, Figure 12The system employs dual channels to simultaneously input different coded signals, with each channel at the output end being normalized and used for decision-making. For example: (a) input [1000001000000], output [1000110110000]; (b) input [0001000001000], output [0110110110110]; (c) input [0000001000001], output [0000110110001]. Results show that this structure supports multi-input, multi-modal parallel encoding, with stable output and good robustness.

[0121] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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 one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0122] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A grating encoder characterized by, The grating encoder comprises: a light signal input end, a mode regulation area and a light signal output end, a light signal input from the light signal input end is output from the light signal output end after passing through the mode regulation area; wherein the mode regulation area comprises: a substrate, at least two straight waveguides and at least one subwavelength grating waveguide; the at least two straight waveguides and the at least one subwavelength grating waveguide are alternately and equally spaced arranged on the substrate; each waveguide starts with a straight waveguide and ends with a straight waveguide; A subwavelength grating waveguide and a straight waveguide arranged alternately with the subwavelength grating waveguide together constitute a unit cell, and each single unit cell contains a normalized flux .

2. The optical encoder of claim 1, wherein, a duty cycle of a subwavelength grating waveguide in a unit in which the subwavelength grating waveguide, a straight waveguide alternately arranged with the subwavelength grating waveguide and a space between the subwavelength grating waveguide and the straight waveguide are included is 0.5; 3. The optical encoder of claim 1, wherein, a straight waveguide arranged in front and a subwavelength grating waveguide arranged after the straight waveguide form a unit cell.

4. The optical encoder of claim 1, wherein, A period of the subwavelength grating waveguide is 0.3 μm.

5. The optical encoder of claim 4, wherein, A space between a straight waveguide and an adjacent subwavelength grating waveguide ranges from 180 nm to 380 nm.

6. The optical encoder of claim 1, wherein, The space between the straight waveguide and the adjacent subwavelength grating waveguide is 280 nm.

7. The optical encoder of claim 1, wherein, Lengths of the at least two straight waveguides and the at least one subwavelength grating waveguide in a waveguide propagation direction are 20 μm, a width of the subwavelength grating waveguide is 0.6 μm and a width of the straight waveguide is 114 nm.

8. The optical encoder of any one of claims 1 to 7, wherein, A height of the at least two straight waveguides and the at least one subwavelength grating waveguide is 0.6 μm.

9. An encoding method characterized by comprising: The substrate is made of silicon dioxide and the at least two straight waveguides and the at least one subwavelength grating waveguide are made of silicon. The grating encoder comprises: at the light signal output end of the grating encoder, collecting light intensities of each waveguide in the mode regulation area of the grating encoder, wherein the grating encoder is any one of the grating encoders in claims 1 to 8; comparing the collected light intensities with a preset threshold value, and obtaining an encoding value based on a comparison result.

Images