Broadband sub-wavelength cross section heterogeneous three-dimensional waveguide end-fire array and working method thereof

Abstract

The invention belongs to the field of semiconductor photoelectrons, and particularly relates to a broadband sub-wavelength cross section heterogeneous three-dimensional waveguide end-fire array, which is characterized in that a right-hand rectangular coordinate system OXYZ is established, and the X axis is defined as a light propagation main axis direction; and five planes whose key points are perpendicular to the X axis are arranged on the X axis, through three-dimensional waveguide path design, space flexible layout is realized on the premise of keeping the structure compact, the integration density is remarkably improved, and the requirements of scenes such as high-channel-number and high-resolution laser radars on high-density integration can be met. A two-dimensional end-fire OPA array often sacrifices isolation in order to realize sub-wavelength spacing, resulting in crosstalk enhancement and beam quality reduction; according to the scheme, the adjacent waveguides adopt heterogeneous cross section design, mode overlapping is reduced by utilizing effective refractive index difference and mode field distribution difference, a mode field integral value is reduced, crosstalk is inhibited from a physical mechanism, the channel isolation is improved, and the beam shaping precision and the main lobe directional diagram purity are further improved.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor optoelectronics, and in particular to a broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array and a working method thereof. Background Art

[0002] Beam steering, a key technology in LiDAR systems, directly impacts the system's resolution, scanning speed, and detection range. Traditional LiDARs often rely on mechanical scanning, which presents challenges such as complex structure, slow response, and poor reliability. With the advancement of silicon-based photonic integration technology, beam steering solutions based on on-chip optical phased arrays (OPAs) have become a hot topic in research and application. Due to their small size, fast response, lack of moving parts, and ease of large-scale integration, they are particularly suitable for LiDAR systems requiring high integration and low power consumption.

[0003] Currently, mainstream optical phased array technology solutions mainly include one-dimensional arrays and two-dimensional arrays:

[0004] One-dimensional optical phased array (1DOPA): Typically composed of a row of emitting elements arranged along a single direction, these emitting elements can be vertically emitting gratings, end-fire waveguides, or metasurface structures. By controlling the phase of light emitted by each emitting element, the outgoing light wavefront is modulated, thereby achieving beam deflection control in a single spatial dimension (e.g., azimuth). This type of structure is mature and easy to implement, but its scanning capability is limited, making it suitable only for linear or single-axis scanning scenarios.

[0005] Two-dimensional optical phased array (2DOPA): To enhance spatial scanning capabilities, a two-dimensional OPA employs a matrix-arranged emitting unit structure, typically consisting of an on-chip two-dimensional grating array or end-fire waveguide array. By precisely controlling the phase of each unit, flexible beam steering is achieved in both azimuth and elevation. In addition to direct two-dimensional phased control, there is also a hybrid control method that uses a row of linear array emitting units to control the elevation angle by adjusting the emission wavelength (based on the principle of wavelength dispersion). This is combined with phase adjustment of the emitting units to achieve azimuth control, thereby indirectly achieving two-dimensional scanning capabilities.

[0006] To this end, the present invention provides a broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array and an operating method thereof. Summary of the Invention

[0007] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0008] The technical solution adopted by the present invention to solve the technical problem is as follows: a broadband subwavelength cross-section heterogeneous three-dimensional waveguide end-fire array described in the present invention establishes a right-handed rectangular coordinate system O-XYZ, where the X-axis is defined as the main axis of light propagation; five key planes perpendicular to the X-axis are set on the X-axis, located at positions x=-a, 0, b, c, and d respectively, and the port cross-section of the three-dimensional waveguide array is defined on each plane. The three-dimensional waveguide array consists of M rows and N columns, with a total of M×N main waveguide units, which are divided into the following functional segments along different regions:

[0009] The port coupling array is located in the region from x=c to x=d. This region is the optical input and output interface of the array and is designed as a one-dimensional uniform waveguide array for efficient coupling with the optical coupler array on the edge of the chip.

[0010] The port rearrangement array is located in the region from x=b to x=c. This structure is used to rearrange the previous one-dimensional port array into a two-dimensional square matrix to adapt to the subsequent three-dimensional convergence operation.

[0011] The converging array, located in the region from x = 0 to x = b, further converges the optical signals in the two-dimensional rearranged array to sub-wavelength spacing, achieving high-density output in a compact space. The cross-section of each waveguide gradually transitions in this region, continuously transforming from a standard shape at x = b to a heterogeneous cross-section at x = 0. In the waveguide array at x = 0, adjacent waveguides have different cross-sections, reducing propagation mode coupling.

[0012] The emission end adjustment array is located in the area from x=-a to x=0. This section is shorter and is mainly used to adjust the final output light direction. The cross-sectional shape of this section of the waveguide is exactly the same as the corresponding waveguide at x=0.

[0013] Preferably, adjacent waveguides have different cross-sectional shapes to reduce the spatial overlap of the mode fields between adjacent waveguides, thereby reducing the mode field integral value.

[0014] A method for operating a broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array, the method comprising the following steps:

[0015] S1. Optical signal injection: The incident optical signal is coupled into the port coupling array located in the x=d plane in a one-dimensional form from an external light source, such as an optical fiber array, edge coupler, or collimator array;

[0016] S2, one-dimensional to two-dimensional rearrangement: The injected optical signal propagates along the waveguide to the rearrangement section from x=c to x=b. At this stage, the waveguide turns and the spacing is widened, forming a two-dimensional grid structure;

[0017] S3, Convergence: The rearranged two-dimensional array optical signal enters the convergence section from x=b to x=0. The waveguide cross-sectional size and shape gradually change along the transmission direction, reaching the target heterogeneous cross-sectional shape at x=0.

[0018] S4, final emission adjustment: The optical signal enters the emission end adjustment array from x = 0 to x = -a. This section is short and is mainly used to fine-tune the alignment direction.

[0019] S5. Final emission: The optical signal is emitted from the emission end facet located at x = −a. Due to the cross-sectional heterogeneity and spatial compactness of the waveguides in each channel, the emitted light forms a highly directional, low-crosstalk, multi-channel parallel beam array, which can be used for optical phased array emission arrays.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The present invention describes a broadband, subwavelength-cross-section heterogeneous three-dimensional waveguide end-fire array and its operating method. Conventional optical phased arrays (OPAs) are mostly two-dimensional planar structures, and their channel layout is limited by the number of process layers and wiring density. This solution, through three-dimensional waveguide path design, achieves flexible spatial layout while maintaining a compact structure, significantly improving the integration density and meeting the high-density integration requirements of scenarios such as high-channel count and high-resolution lidar.

[0022] 2. The present invention describes a broadband subwavelength cross-section heterogeneous three-dimensional waveguide end-fire array and its working method. In order to achieve subwavelength spacing, two-dimensional end-fire OPA arrays often sacrifice isolation, resulting in enhanced crosstalk and reduced beam quality. In this scheme, adjacent waveguides adopt a heterogeneous cross-section design, and the difference in effective refractive index and mode field distribution is used to reduce modal overlap, reduce the mode field integral value, suppress crosstalk from a physical mechanism, enhance channel isolation, and thereby improve beam shaping accuracy and main lobe pattern purity.

[0023] 3. The present invention describes a broadband subwavelength cross-section heterogeneous three-dimensional waveguide end-fire array and its working method. Traditional OPAs require complex structures or dispersion designs to achieve beam compression and broadband response. The structure of this solution naturally supports subwavelength-level spacing arrangement, and the optical signal is directly end-fired without frequency selectivity restrictions. It has ultra-wideband characteristics and multi-wavelength compatibility, and can be used in scenarios such as wide-spectrum signal processing, multi-band lidar, and optical frequency division multiplexing.

[0024] 4. The present invention describes a broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array and its working method. Some traditional OPA schemes achieve pitch angle control through wavelength tuning, resulting in the coupling of beam direction and wavelength, which limits the independent operation of multiple wavelengths. This scheme directly realizes azimuth and pitch two-dimensional beam steering through a three-dimensional structure combined with independent phase control, avoiding wavelength dependence, supporting multi-wavelength parallel beam control, and improving the system's flexibility in optical phased array transmission / reception scenarios.

[0025] 5. The present invention describes a broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array and its operating method. Traditional OPA structures rely on high-precision planar etching and coupling window alignment, which makes them difficult to manufacture. This solution is adapted to high-resolution additive manufacturing technologies such as two-photon polymerization (TPP) and can form a complete three-dimensional waveguide array in one step. It has a simple manufacturing process, high alignment accuracy, and is compatible with photonic integrated circuits, with the potential for lower cost and higher volume production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] Figure 1 is a 3D schematic diagram of the three-dimensional waveguide in the present invention;

[0028] Figure 2 Schematic diagram of the waveguide cross section at x=c and x=d in the present invention;

[0029] Figure 3 Schematic diagram of the waveguide cross section at x=b in the present invention;

[0030] Figure 4 This is a schematic diagram of generating different cross sections of adjacent waveguides at x=0 in the present invention. DETAILED DESCRIPTION

[0031] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0032] like Figures 1 to 4 As shown, a broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array according to an embodiment of the present invention establishes a right-handed rectangular coordinate system O-XYZ, where the X-axis is defined as the main axis of light propagation. Five key planes perpendicular to the X-axis are set on the X-axis, located at positions x=-a, 0, b, c, and d, respectively. The port cross-section of the three-dimensional waveguide array is defined on each plane. The three-dimensional waveguide array consists of M rows and N columns, with a total of M×N main waveguide units, which are divided into the following functional segments along different regions:

[0033] The port coupling array is located in the region from x=c to x=d. This region is the optical input and output interface of the array and is designed as a one-dimensional uniform waveguide array for efficient coupling with the optical coupler array on the edge of the chip. The cross-sectional shape of this section of waveguide is completely consistent, and the arrangement spacing can match that of a standard optical fiber array or edge coupler. Figure 2 As shown;

[0034] The port rearrangement array is located in the region from x=b to x=c. This section of the structure is used to rearrange the previous one-dimensional port array into a two-dimensional square array to adapt to the subsequent three-dimensional convergence operation. The cross-sections of the waveguides in this section are consistent, and the spacing between the waveguides is usually hundreds of times the working wavelength. Figure 3 As shown;

[0035] The converging array, located in the region from x = 0 to x = b, further converges the optical signals in the two-dimensional rearranged array to sub-wavelength spacing, achieving high-density output in a compact space. The cross-section of each waveguide gradually transitions in this region, continuously transforming from a standard shape at x = b to a heterogeneous cross-section at x = 0. In the waveguide array at x = 0, adjacent waveguides have different cross-sections, reducing propagation mode coupling. Figure 4 A typical heterogeneous unit arrangement is demonstrated: the cross-section of each waveguide is different from that of its four adjacent waveguides above, below, left, and right, forming a minimum repeatable unit that can be laid out in a translational manner to fill a square grid.

[0036] The emission end adjustment array is located in the area from x=-a to x=0. This section is shorter and is mainly used to adjust the final output light direction. The cross-sectional shape of this section of the waveguide is exactly the same as the corresponding waveguide at x=0.

[0037] All broken line connections in the waveguide paths are transitioned using smooth curves, and reasonable spacing is maintained between all waveguides to ensure that there are no physical intersections in the structure.

[0038] Adjacent waveguides have different cross-sectional shapes to reduce the spatial overlap of the mode fields between adjacent waveguides, thereby reducing the mode field integral value. At the same time, due to the difference in effective refractive index caused by different cross-sectional shapes, the crosstalk level between waveguides is reduced.

[0039] A method for operating a broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array, the method comprising the following steps:

[0040] S1. Optical signal injection: The incident optical signal is coupled from an external light source, such as an optical fiber array, edge coupler, or collimator array, into the port coupling array located in the x=d plane in a one-dimensional form. This section of waveguide is arranged regularly, with the same cross-sectional shape and spacing matching the optical fiber or chip port array, achieving efficient and low-loss optical energy injection.

[0041] S2, 1D to 2D rearrangement: The injected optical signal propagates along the waveguide to the rearrangement section from x=c to x=b. During this stage, the waveguides turn and become spaced apart, forming a 2D grid structure. The waveguides maintain the same cross-section, and the topological reconstruction from linear arrangement to matrix arrangement is completed through the rotation and offset of the geometric path.

[0042] S3. Convergence: The rearranged two-dimensional array optical signal enters the convergence section from x=b to x=0. The waveguide cross-sectional size and shape gradually change along the transmission direction, reaching the target heterogeneous cross-sectional shape at x=0. This section gradually compresses the original larger spacing to a subwavelength spacing while controlling the change in mode field morphology to achieve a high-density output arrangement. The heterogeneous cross-section plays a role in suppressing crosstalk in this area. Since the effective refractive index and mode field distribution of each waveguide are different, the coupling between adjacent modes is significantly reduced.

[0043] S4, Final emission adjustment: The optical signal enters the emission end adjustment array from x = 0 to x = -a. This section is short and is mainly used to fine-tune the alignment direction. The waveguide cross-section of this section is the same as that at x = 0, and the path is designed with a slight bend or tilt to adjust the output light direction or far-field interference characteristics.

[0044] S5. Final emission: The optical signal is emitted from the emission end facet located at x = −a. Due to the cross-sectional heterogeneity and spatial compactness of the waveguides in each channel, the emitted light forms a highly directional, low-crosstalk, multi-channel parallel beam array, which can be used for an optical phased array transmit array; based on the reversibility of the optical path, this transmit array can also be used as a receive array.

[0045] Specifically,

[0046] 1. Working principle:

[0047] (1) Structural design support principles

[0048] Coordinate System and Functional Segmentation: A right-handed rectangular coordinate system O−XYZ is established, with the X-axis as the principal axis of light propagation. Five key planes are set along the X-axis at positions x=−a, 0, b, c, and d to define the port cross-section of the three-dimensional waveguide array. The array consists of M rows and N columns of M×N main waveguide elements. These elements are divided into four functional segments: the port coupling array, the port rearrangement array, the convergence array, and the emission end adjustment array. Each segment is connected by smooth curved transition lines to ensure no physical intersections between waveguides.

[0049] Heterogeneous cross-section design: Adjacent waveguides have different cross-sectional shapes. By utilizing the differences in effective refractive index and mode field distribution, the spatial overlap of the mode fields between adjacent waveguides is reduced, the mode field integral value is reduced, and the crosstalk level between waveguides is reduced.

[0050] (2) Principles of optical signal transmission and processing

[0051] Optical signal injection (S1): The incident light signal is coupled one-dimensionally from an external light source such as a fiber array, edge coupler, or collimator array into the port coupling array located in the x = d plane. This waveguide segment is arranged in a regular pattern with a uniform cross-sectional shape and a spacing that matches the fiber or chip port array, achieving efficient and low-loss optical energy injection.

[0052] One-dimensional to two-dimensional rearrangement (S2): The injected optical signal propagates along the waveguide to the rearrangement section from x=c to x=b. The waveguide turns and widens the spacing. Through the rotation and offset of the geometric path, a two-dimensional grid structure is formed, completing the topological reconstruction from linear arrangement to matrix arrangement.

[0053] Convergence (S3): The rearranged 2D array optical signal enters the convergence section from x = b to x = 0. The waveguide cross-sectional size and shape gradually change along the transmission direction, reaching the target heterogeneous cross-sectional shape at x = 0. This section gradually compresses the original large spacing to subwavelength spacing while controlling the change in mode field morphology to achieve a high-density output arrangement. The heterogeneous cross-sectional shape in this region suppresses crosstalk.

[0054] Final emission adjustment (S4): The optical signal enters the emission end adjustment array from x=0 to x=-a. This section is shorter, and the waveguide cross-section shape is the same as that at x=0. The path is designed to be slightly curved or tilted to fine-tune the alignment direction and adjust the output light direction or far-field interference characteristics.

[0055] Final emission (S5): The optical signal is emitted from the emission end facet located at x = −a. Due to the cross-sectional heterogeneity and spatial compactness of the waveguides in each channel, the emitted light forms a highly directional, low-crosstalk, multi-channel parallel beam array, which can be used for optical phased array transmission arrays and, based on the reversibility of the optical path, can also be used as a receiving array.

[0056] 2. Benefits and advantages of design

[0057] (1) Structural design

[0058] Suppressing crosstalk and improving signal quality: Adjacent waveguides adopt a heterogeneous cross-section design, utilizing differences in effective refractive index and mode field distribution to reduce modal overlap, suppressing crosstalk through a physical mechanism, improving channel isolation and optical signal quality, and enhancing beam shaping accuracy and main lobe pattern purity.

[0059] Three-dimensional structure, efficient space utilization: Expanding from the traditional two-dimensional planar structure to a three-dimensional structure, through the three-dimensional waveguide path design, flexible spatial layout can be achieved while maintaining a compact structure, significantly improving the integration density, and meeting the integration density requirements of future high-channel count, high-resolution lidar, etc.

[0060] Subwavelength spacing arrangement: Supports high-density, subwavelength spacing waveguide output arrays without complex structures, providing a basis for applications such as high-resolution imaging.

[0061] (2) Functional performance

[0062] Ultra-wideband characteristics: Since the optical signal is directly emitted from the waveguide, the structure naturally has ultra-wideband characteristics and no frequency selectivity restrictions. It is suitable for scenarios that require broadband operation, such as wide-spectrum signal processing and optical communications.

[0063] Multi-wavelength compatibility: Compatible with multi-wavelength operation, it can achieve independent beam control and broadband scanning at multiple wavelengths. It has good spectrum coverage and wavelength multiplexing potential, and is suitable for applications such as multi-band lidar or optical frequency division multiplexing.

[0064] Two-dimensional large-angle beam scanning capability: The phase on each waveguide can be independently controlled. Combined with the high-density array arrangement with sub-wavelength spacing, it has two-dimensional large-angle beam scanning capability without introducing dispersion wavelength control, avoiding the coupling of beam direction and wavelength, facilitating multi-wavelength parallel beam control, and improving system flexibility.

[0065] Improved beam quality: The half-wavelength array helps to increase the energy concentration of the mainlobe pattern, suppress sidelobe power leakage, and significantly improve beam quality and spatial resolution.

[0066] 3. Manufacturing process

[0067] Strong adaptability and easy manufacturing and integration: It can be directly adapted to high-resolution additive manufacturing technologies such as two-photon polymerization (TPP), has good 3D printing formability and batch manufacturing potential, can form a complete 3D waveguide array in one step, is easy to manufacture, has high alignment accuracy, and is compatible with photonic integrated circuits. Compared with traditional structures that rely on high-precision planar etching and coupling window alignment, it has greater potential for batch production and low-cost implementation.

[0068] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array, characterized in that: A right-handed rectangular coordinate system O−XYZ is established, where the X-axis is defined as the principal axis of light propagation. Five key planes perpendicular to the X-axis are set on the X-axis, located at positions x=−a, 0, b, c, and d, respectively. Each plane defines the port cross-section of the three-dimensional waveguide array. The three-dimensional waveguide array consists of M rows and N columns, with a total of M×N main waveguide units. Different regions are divided into the following functional segments: The port coupling array is located in the region from x=c to x=d. This region is the optical input and output interface of the array and is designed as a one-dimensional uniform waveguide array for efficient coupling with the optical coupler array on the edge of the chip. The port rearrangement array is located in the region from x=b to x=c. This structure is used to rearrange the previous one-dimensional port array into a two-dimensional square matrix to adapt to the subsequent three-dimensional convergence operation. The converging array, located in the region from x = 0 to x = b, further converges the optical signals in the two-dimensional rearranged array to sub-wavelength spacing, achieving high-density output in a compact space. The cross-section of each waveguide gradually transitions in this region, continuously transforming from a standard shape at x = b to a heterogeneous cross-section at x = 0. In the waveguide array at x = 0, adjacent waveguides have different cross-sections, reducing propagation mode coupling. The emission end adjustment array is located in the area from x=-a to x=0. This section is shorter and is mainly used to adjust the final output light direction. The cross-sectional shape of this section of the waveguide is exactly the same as the corresponding waveguide at x=0.

2. The broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array according to claim 1, characterized in that: Adjacent waveguides have different cross-sectional shapes to reduce the spatial overlap of mode fields between adjacent waveguides, thereby reducing the mode field integral value.

3. A method for operating a broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array, which is used for the broadband sub-wavelength cross-section heterogeneous three-dimensional waveguide end-fire array according to any one of claims 1-2, characterized in that: The working method comprises the following steps: S1. Optical signal injection: The incident optical signal is coupled from an external light source, such as an optical fiber array, edge coupler, or collimator array, into the port coupling array located in the x=d plane in a one-dimensional form. This section of waveguide is arranged regularly, with the same cross-sectional shape and spacing matching the optical fiber or chip port array, achieving efficient and low-loss optical energy injection. S2, 1D to 2D rearrangement: The injected optical signal propagates along the waveguide to the rearrangement section from x=c to x=b. During this stage, the waveguides turn and become spaced apart, forming a 2D grid structure. The waveguides maintain the same cross-section, and the topological reconstruction from linear arrangement to matrix arrangement is completed through the rotation and offset of the geometric path. S3, Convergence: The rearranged two-dimensional array optical signal enters the convergence section from x=b to x=0. The waveguide cross-sectional size and shape gradually change along the transmission direction, reaching the target heterogeneous cross-sectional shape at x=0. This section gradually compresses the original large spacing to a subwavelength spacing while controlling the change in mode field morphology to achieve a high-density output arrangement. The heterogeneous cross-sectional area suppresses crosstalk in this region, and since each waveguide has a different effective refractive index and mode field distribution, the coupling between adjacent modes is significantly reduced. S4, Final emission adjustment: The optical signal enters the emission end adjustment array from x = 0 to x = -a. This section is short and is mainly used to fine-tune the alignment direction. The waveguide cross-section of this section is the same as that at x = 0, and the path is designed with a slight bend or tilt to adjust the output light direction or far-field interference characteristics. S5. Final emission: The optical signal is emitted from the emission end facet located at x = −a. Due to the cross-sectional heterogeneity and spatial compactness of the waveguides in each channel, the emitted light forms a highly directional, low-crosstalk, multi-channel parallel beam array, which can be used for an optical phased array transmit array; based on the reversibility of the optical path, this transmit array can also be used as a receive array.

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