Light beam splitter structure and array thereof

Abstract

The invention discloses an optical beam splitter structure and an array thereof, a beam splitter body is asymmetrically arranged about a central axis, an asymmetrical multimode interference beam splitter is adopted, asymmetrical light intensity distribution is generated in a multimode interference area, asymmetrical interference degree and power distribution in a power distribution area are adjusted, and non-uniform beam splitting is realized. High-difficulty machining is avoided, and insertion loss is low. The adjustable beam splitting ratio is realized by adjusting the asymmetric structure form of the multimode interference beam splitter. A multi-stage array formed by cascading asymmetric multimode interference beam splitters is adopted, one beam of laser energy is distributed to N output ports, light intensity distribution output by the waveguide array is non-uniform amplitude distribution, and high processing tolerance and wide bandwidth are achieved. According to the method, the diffraction effect generated by uniform amplitude distribution output by the waveguide array is solved, and the optical power of the lithium niobate optical phased array is concentrated towards a main lobe, so that the main lobe power and the side lobe suppression ratio are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical processing devices, and particularly relates to an optical beam splitter structure and its array. Background Technique

[0002] Optical Phased Array (OPA) is a fully solid-state beam scanning technology with high-speed scanning ability and anti-interference performance. Sidelobes are non-main lobe radiations generated by the optical phased array in the far field, which not only consume the main lobe power of the output beam but also lead to a decrease in beam quality and a reduction in scanning accuracy. How to reduce the sidelobe suppression ratio of the output beam is one of the main problems in improving the performance of OPA.

[0003] Existing optical phased arrays use multiple cascades of optical beam splitters with an energy distribution ratio of 1:1 to distribute the input beam to the waveguide array. The optical beam splitter with an energy ratio of 1:1 makes the energy amplitude of the output beam of the waveguide array present a rectangular distribution. There is an amplitude truncation at the edge of this rectangular amplitude beam energy, that is, there is an energy value jump. The amplitude truncation phenomenon causes diffraction of the far-field light wave, resulting in a reduction in the main lobe power of the far field of the optical phased array and a decrease in the sidelobe suppression ratio.

[0004] Therefore, designing a non-uniform optical beam splitter and its array to generate a non-uniform amplitude distribution can solve the problem of amplitude truncation at the edge of the rectangular amplitude beam energy and weaken the diffraction effect of the far-field light wave caused by amplitude truncation, thereby improving the main lobe energy and far-field sidelobe suppression ratio of the optical phased array.

[0005] Currently, the implementation methods of non-uniform optical beam splitters and their arrays are as follows: Non-uniform optical power splitter of multimode interference coupler: The literature "Ultra-compact low-loss variable-ratio 1×2 power splitter with ultra-low phase deviation based on asymmetric ladder-shaped multimode interference coupler," Optics Express, 2020, 28, 34137-34146 proposed a non-uniform optical power splitter based on a multimode interference coupler. By removing a part of the area on one side of the multimode interference region, the structural symmetry of the multimode interference region is broken, resulting in an asymmetric light intensity distribution and realizing a non-uniform optical power splitter. However, the splitting ratio of this scheme is positively correlated with the removed area, and the removed area directly determines the insertion loss of the device. Therefore, when a large splitting ratio is achieved, there is a large insertion loss. The existing non-uniform optical power splitter array adopts a non-uniform optical power splitter array with Y-branches. By cascading the head and tail, a non-uniform amplitude distribution of multiple channels is realized. However, in this scheme, the asymmetric profile of the asymmetric Y-branch power splitter is a Bessel curve, which has a large processing difficulty and insertion loss, and the cascaded power splitter array has a problem of narrow bandwidth. Summary of the Invention

[0006] The object of the present invention is to provide an optical power splitter structure and its array to overcome the problems of high insertion loss and narrow bandwidth in the existing optical power splitter structure.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: An optical power splitter structure includes a power splitter body, which includes an input channel, a power distribution region, and an output channel connected in sequence. The input channel, the power distribution region, and the output channel are arranged along the central axis; the power splitter body is asymmetrically arranged with respect to the central axis, and the output channel includes a first output channel and a second output channel.

[0008] Preferably, only two of the input channel, the power distribution region, and the output channel are symmetrically arranged with respect to the central axis at the same time.

[0009] Preferably, the power distribution region includes a third region, and the upper and lower sides of one end of the third region close to the input channel are a first region and a second region respectively.

[0010] Preferably, the cross-sectional area shapes of the first region and the second region are rectangular, square, triangular, trapezoidal, or circular.

[0011] Preferably, the cross-sectional areas of the first region and the second region are different, the input channel is symmetrically arranged about the central axis, and the first output channel and the second output channel are symmetrically distributed about the central axis.

[0012] Preferably, the cross-sectional areas of the first region and the second region are equal, and the third region is symmetrically arranged along the central axis; when the input channel is symmetrically arranged about the central axis, the first output channel and the second output channel are asymmetrically arranged about the central axis; when the input channel is asymmetrically arranged about the central axis, the first output channel and the second output channel are symmetrically arranged about the central axis.

[0013] An optical beam splitter structure array includes an optical beam splitter with uniform beam splitting, a first beam splitter array, and a second beam splitter array; the first-order beam splitter is an optical beam splitter with uniform beam splitting, the first beam splitter array and the second beam splitter array are respectively cascaded at the output end of the optical beam splitter with uniform beam splitting, and the first beam splitter array and the second beam splitter array are symmetric about the central symmetry line of the array.

[0014] Preferably, the first beam splitter array and the second beam splitter array are the same, and the first beam splitter array is formed by cascading a plurality of the above-mentioned optical beam splitter structures end to end.

[0015] Preferably, the first beam splitter array includes a second-order cascaded optical beam splitter structure, the output end of the second-order cascaded optical beam splitter structure is cascaded with a third-order cascaded optical beam splitter structure, and the output end of the third-order cascaded optical beam splitter structure is sequentially cascaded with a plurality of optical beam splitter structures.

[0016] Preferably, the beam splitting ratio of the optical beam splitter with uniform beam splitting at the first order is 0.5, the beam splitting ratio of the second-order cascaded optical beam splitter structure is in the range of 0.5 - 0.8, the beam splitting ratio of the third-order cascaded optical beam splitter structure is in the range of 0.5 - 0.7, and the beam splitting ratio of the optical beam splitter structure closer to the central symmetry line is less than that of the optical beam splitter structure farther from the central symmetry line; the beam splitting ratios of the optical beam splitter structures connected to the rear end of the third-order cascaded optical beam splitter structure are all less than 0.6.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: An optical beam splitter structure of the present invention, the beam splitter body includes an input channel, a power distribution region and an output channel connected in sequence, and the input channel, the power distribution region and the output channel are arranged along the central axis; the beam splitter body is asymmetrically arranged about the central axis. By breaking the structural symmetry of the multimode interference beam splitter and adopting an asymmetric multimode interference beam splitter, an asymmetric light intensity distribution is generated in the multimode interference region, and the asymmetric interference degree and power distribution in the power distribution region are adjusted, so that an adjustable beam splitting ratio can be realized, and the structure is simple, avoiding difficult processing; compared with the traditional non-uniform beam splitter with unilateral resection, which has a large insertion loss when realizing a large beam splitting ratio, the present invention has a lower insertion loss.

[0018] Preferably, the shapes of the first output channel and the second output channel are inverted cones, which is beneficial to reducing the loss between the first output channel, the second output channel and the power distribution region.

[0019] A beam splitter structure array can realize an adjustable beam splitting ratio by adjusting the asymmetric structural form of the multimode interference beam splitter. An asymmetric multimode interference beam splitter cascaded multi-stage array is adopted to distribute the energy of a laser beam to N output ports, so that the light intensity distribution output by the waveguide array is a non-uniform amplitude distribution. This method solves the diffraction effect caused by the uniform amplitude distribution output by the waveguide array, makes the optical power of the lithium niobate optical phased array concentrate on the main lobe, thereby significantly improving the main lobe power and side lobe suppression ratio; compared with the traditional non-uniform beam splitter array using Y-branch beam splitters in cascade, which has high processing difficulty and narrow bandwidth problems, the present invention has high processing tolerance and wide bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0021] Figure 1 It is an optical beam splitter structure for realizing non-uniform light splitting proposed in the present invention.

[0022] Figure 2 It is an optical beam splitter array structure for non-uniform light splitting proposed in the present invention.

[0023] Figure 3 It is a schematic diagram of an optical beam splitter structure with a non-uniform structure provided in Embodiment 1.

[0024] Figure 4It is the electric field distribution of a non-uniform optical beam splitter provided in Embodiment 1 and the optical intensity distributions of two output ports.

[0025] Figure 5 It is the one-dimensional normalized optical intensity distributions of two output ports of a non-uniform optical beam splitter provided in Embodiment 1; Figure 6 It is a schematic diagram of the structure of a non-uniform optical beam splitter provided in Embodiment 2.

[0026] Figure 7 It is the electric field distribution of a non-uniform optical beam splitter provided in Embodiment 2 and the optical intensity distributions of two output ports.

[0027] Figure 8 It is the one-dimensional normalized optical intensity distributions of two output ports of a non-uniform optical beam splitter provided in Embodiment 1; Figure 9 It is a schematic diagram of the structure of a non-uniform optical beam splitter provided in Embodiment 3.

[0028] Figure 10 It is the electric field distribution of a non-uniform optical beam splitter provided in Embodiment 3 and the optical intensity distributions of two output ports.

[0029] Figure 11 It is the one-dimensional normalized optical intensity distributions of two output ports of a non-uniform optical beam splitter provided in Embodiment 3; Figure 12 It is a schematic diagram of the waveguide structure of a non-uniform optical beam splitter provided in Embodiments 1, 2, and 3.

[0030] Figure 13 It is a beam splitter array structure with a Gaussian amplitude distribution provided in Embodiment 4.

[0031] Figure 14 It is a Gaussian amplitude distribution and a uniform amplitude distribution provided in Embodiment 4.

[0032] Figure 15 It is the one-dimensional near-field intensity distribution of a Gaussian amplitude distribution and a uniform amplitude distribution provided in Embodiment 4.

[0033] Figure 16 It is the far-field distribution of a Gaussian amplitude distribution and a uniform amplitude distribution provided in Embodiment 4.

[0034] Figure 17 It is the relationship between the beam splitting ratio and wavelength of a non-uniform beam splitter provided in Embodiment 4.

[0035] Figure 18 It is the simulation results and measured results of a Gaussian amplitude distribution provided in Embodiment 4.

[0036] Figure 19 It is the beam splitting ratio distribution of the beam splitters in the 16-channel beam splitter array provided in Embodiment 4.

[0037] In the figure: 1 - input channel, 2 - power distribution region, 3 - output channel, 4 - central symmetry line of the structure, 21 and 22 - removal regions, 23 - asymmetric power distribution region, 5 - optical beam splitter with uniform light splitting, 6 - optical beam splitter structure, 6010 - second-stage cascaded optical beam splitter structure, 6020 - third-stage cascaded optical beam splitter structure, 601 - first beam splitter array, 602 - second beam splitter array, 7 - central symmetry line of the array, 8 - loaded waveguide layer, 9 - thin film lithium niobate layer, 10 - buried layer, 11 - substrate layer. Detailed implementation manners

[0038] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0040] In the specific implementation manner of the present invention, an optical beam splitter structure is provided, such as Figure 1As shown, it includes an input channel 1, a power distribution area 2, and an output channel 3 connected in sequence. The power distribution area 2 includes a third area 23. On the upper and lower sides of one end of the third area 23 close to the input channel 1 are a first area 21 and a second area 22 respectively. The first area 21 and the second area 22 are removal areas, that is, two parts are removed at one end of the third area 23 to form the first area 21 and the second area 22 respectively; the output channel 3 includes a first output channel 31 and a second output channel 32; the input channel 1, the power distribution area 2, and the output channel 3 are arranged along the central axis 4; the beam splitter body is asymmetrically arranged with respect to the central axis 4, that is, the input channel 1, the power distribution area 2, and the output channel 3 are not symmetrically arranged along the central axis 4 at the same time.

[0041] The cross-sectional area shapes of the first area 21 and the second area 22 are specifically rectangles, squares, triangles, trapezoids, or circles.

[0042] In the specific implementation manner of the present application, as Figure 3 , Figure 9 shown, when the cross-sectional areas of the first area 21 and the second area 22 are equal, the third area 23 is a structure symmetric along the central axis 4. The input channel 1 is located on one side of the central axis 4 of the structure, or the first output channel 31 and the second output channel 32 are asymmetrically distributed along the central axis 4. More preferably, the asymmetric distribution of the first output channel 31 and the second output channel 32 along the central axis 4 of the structure includes that the positions of the first output channel 31 and the second output channel 32 are asymmetrically distributed along the central axis 4 of the structure, and the widths of the first output channel 31 and the second output channel 32 are different, resulting in an asymmetric distribution along the central axis 4 of the structure.

[0043] As Figure 6 shown, when the cross-sectional areas of the first area 21 and the second area 22 are different, the third area 23 is an asymmetric structure along the central axis 4 of the structure. The input channel 1 is located on the central axis 4 of the structure, and the first output channel 31 and the second output channel 32 are symmetrically distributed along the central axis 4 of the structure.

[0044] The positions of the first area 21 and the second area 22 can be located at any position within the power distribution area 2.

[0045] The equality of the cross-sectional areas of the first area 21 and the second area 22 includes two cases. The cross-sectional areas of the first area 21 and the second area 22 are equal and equal to 0, and the cross-sectional areas of the first area 21 and the second area 22 are equal and not equal to 0, that is, S21 = S22 = 0 and S21 = S22 ≠ 0; The shapes of the first area 21 and the second area 22 can be the same shape or different shapes.

[0046] The cross-sectional shapes of the input channel 1 and the output channel 3 are inverted cones, which is beneficial to reducing the loss between the input channel 1 and the output channel 3 and the power distribution region 2.

[0047] When the first region 21 and the second region 22 are the same, the third region 23 has structural symmetry, generating a symmetric interference phenomenon; at this time, the input channel 1 is located on the structural central symmetry axis 4, making the first output channel 31 and the second output channel 32 asymmetrically distributed along the structural central axis 4, resulting in different optical energies output by the first output channel 31 and the second output channel 32, realizing a beam splitter structure with non-uniform beam splitting. Further, by changing the positions of the first output channel 31 and the second output channel 32, an adjustable beam splitting ratio is achieved. At this time, the input channel 1 is offset from the structural central symmetry axis 4, and the first output channel 31 and the second output channel 32 are symmetrically distributed along the structural central axis 4, making the optical energy asymmetrically distributed within the third region 23, resulting in different optical energies output by the first output channel 31 and the second output channel 32, realizing a beam splitter structure with non-uniform beam splitting. Further, by changing the position of the input channel 1, an adjustable beam splitting ratio is achieved.

[0048] When the first region 21 and the second region 22 are different, the structural symmetry of the third region 23 is broken, generating an asymmetric interference phenomenon, resulting in different optical energies output by the first output channel 31 and the second output channel 32 that are symmetrically distributed about the structural central axis 4, realizing a beam splitter structure with non-uniform beam splitting. Further, by changing the areas of the first region 21 and the second region 22, the degree of asymmetric interference and power distribution in the third region 23 are adjusted to achieve an adjustable beam splitting ratio.

[0049] Based on the above-mentioned beam splitter structure array, as Figure 2 shown, it includes a beam splitter 5 with uniform beam splitting, and several cascaded beam splitters 6 with non-uniform beam splitting, which are cascaded by connecting the 3-order beam splitters end to end, and have one input port and eight output ports. The cascading order can be 3-order, but is not limited to 3-order.

[0050] The eight output ports of a beam splitter structure array output a non-uniform amplitude distribution, including an asymmetric amplitude distribution and a symmetric amplitude distribution, where the symmetric amplitude distribution includes Gaussian distribution, Taylor distribution, and Chebyshev distribution.

[0051] More preferably, the method for realizing the symmetric amplitude distribution is: The first-order beam splitter is a beam splitter 5 with uniform beam splitting, which is used to output two beams with the same amplitude. The first beam splitter array 601 and the second beam splitter array 602 are respectively connected to the output end of the beam splitter 5 with uniform beam splitting, and the first beam splitter array 601 and the second beam splitter array 602 are symmetric about the array central symmetry line 7.

[0052] The first beam splitter array 601 is formed by cascading a plurality of the above-mentioned beam splitters with non-uniform beam splitting structures 6 end to end. The second-order beam splitter is a beam splitting structure 6010 with non-uniform beam splitting, and the third-order beam splitters are beam splitting structures 6020 and 6021 with non-uniform beam splitting respectively cascaded at the output end of the beam splitting structure 6010 with non-uniform beam splitting.

[0053] The beam splitting ratio of the first-order beam splitter 5 with uniform beam splitting is 0.5. The beam splitting ratio of the cascaded beam splitting structure 6010 in the second order is in the range of 0.5 - 0.8. The beam splitting ratios of the cascaded beam splitting structures 6020 and 6021 in the third order are in the range of 0.5 - 0.7, and the beam splitting ratio of the beam splitting structure 6021 closer to the central symmetry line 7 is less than that of the beam splitting structure 6020 farther from the central symmetry line 7. The beam splitting ratios of the beam splitting structures connected to the rear end of the cascaded beam splitting structure 6020 in the third order are all less than 0.6, that is, the beam splitting ratios of the cascaded beam splitting structures 6 in the fourth order and higher orders are all less than 0.6.

[0054] Embodiment 1 As Figure 3 shown, this embodiment proposes a beam splitting structure for realizing non-uniform beam splitting, including an input channel 1, a power distribution region 2, and an output channel 3.

[0055] The input channel 1 is offset 3 μm upward relative to the central axis 4 of the structure.

[0056] The areas of both the first region 21 and the second region 22 removed are 0, and the power distribution region 2 is rectangular; The output channel 3 includes a first output channel 31 and a second output channel 32, and the first output channel 31 and the second output channel 32 are symmetrically distributed along the central axis 4 of the structure.

[0057] The shapes of the first output channel 31 and the second output channel 32 are inverted cones, which is beneficial to reducing the loss between the first output channel 31, the second output channel 32 and the power distribution region 2.

[0058] Since the input channel 1 is offset relative to the central axis 4 of the structure, the structural symmetry of the input channel 1 about the central axis 4 of the structure is broken, and an asymmetric interference phenomenon is generated in the power distribution region 2, resulting in different optical energies output from the first output channel 31 and the second output channel 32, and realizing the beam splitting function of non-uniform beam splitting. Further, by changing the offset amount of the input channel 1 relative to the central axis 4 of the structure, the asymmetric interference degree and power distribution in the power distribution region 2 are adjusted to realize an adjustable beam splitting ratio.

[0059] Figure 4 is the electric field distribution of a beam splitter with a non-uniform structure and the optical intensity distributions of two output ports provided in this embodiment. FromFigure 4 It can be seen that since the input channel 1 is located on one side of the structural central axis 4, the structural symmetry of the input channel 1 with respect to the structural central axis 4 is broken, resulting in an asymmetric interference phenomenon in the power distribution region 2, causing different optical energies to be output from the first output channel 31 and the second output channel 32, and realizing the beam splitting function of non-uniform beam splitting.

[0060] Figure 5 It is the one-dimensional optical intensity distribution of the two output ports of a non-uniformly structured optical beam splitter provided in this embodiment. The input channel 1 is offset upward by 3 μm relative to the structural central axis 4, and the beam splitting ratio of the two output channels is 0.84.

[0061] Embodiment 2 As Figure 6 shown, this embodiment proposes an optical beam splitter structure for realizing non-uniform beam splitting, including an input channel 1, a power distribution region 2, and an output channel 3.

[0062] The input channel 1 is located on the structural central axis 4, and the input channel 1 is symmetrically arranged with respect to the central axis 4; The power distribution region 2 includes a first region 21, a second region 22, and a third region 23, where the first region 21 and the second region 22 are removal regions; the first region 21 is rectangular in shape and is located in the upper left corner of the power distribution region 2; the second region 22 is triangular in shape and is located in the lower left corner of the power distribution region 2; The output channel 3 includes a first output channel 31 and a second output channel 32, and the first output channel 31 and the second output channel 32 are symmetrically distributed along the structural central axis 4.

[0063] The first output channel 31 and the second output channel 32 are in an inverted conical shape, which is beneficial to reducing the loss between the first output channel 31, the second output channel 32 and the power distribution region 2.

[0064] Since the first region 21 and the second region 22 are removed, the structural symmetry of the third region 23 is broken, resulting in an asymmetric interference phenomenon, causing different optical energies to be output from the first output channel 31 and the second output channel 32, and realizing the beam splitting function of non-uniform beam splitting. Further, by changing the areas of the first region 21 and the second region 22, the degree of asymmetric interference and power distribution in the third region 23 are adjusted to realize an adjustable beam splitting ratio.

[0065] Figure 7 It is the electric field distribution and the optical intensity distribution of the two output ports of a non-uniformly structured optical beam splitter provided in this embodiment. From Figure 4It can be seen that since the first region 21 and the second region 22 are removed, the structural symmetry of the third region 23 is broken, resulting in an asymmetric interference phenomenon, causing different optical energies to be output from the first output channel 31 and the second output channel 32, and realizing the beam splitting function of non-uniform beam splitting.

[0066] Figure 8 They are the one-dimensional light intensity distributions of the two output ports of a non-uniform structure optical beam splitter provided in this embodiment. The length and width of the first region 21 are 20 μm and 2.6 μm respectively, the length and height of the second region 22 are 18 μm and 2.5 μm respectively, and the beam splitting ratio of the two output channels is 0.66.

[0067] Embodiment 3 As Figure 9 shown, this embodiment proposes an optical beam splitter structure for realizing non-uniform beam splitting, including an input channel 1, a power distribution region 2, and an output channel 3.

[0068] The input channel 1 is symmetric about the structural central axis 4.

[0069] The areas of the first region 21 and the second region 22 removed are both 0, and the power distribution region 2 is rectangular; The output channel 3 includes a first output channel 31 and a second output channel 32, and the first output channel 31 and the second output channel 32 are asymmetrically distributed along the structural central axis 4. The first output channel 31 is located 4 μm above the central axis 4, and the second output channel 32 is located 2.6 μm below the structural central axis 4.

[0070] The shapes of the first output channel 31 and the second output channel 32 are inverted cones, which is beneficial to reducing the loss between the first output channel 31, the second output channel 32 and the power distribution region 2.

[0071] Since the first output channel 31 and the second output channel 32 are asymmetrically distributed about the structural central axis 4, the structural symmetry of the first output channel 31 and the second output channel 32 about the structural central axis 4 is broken, resulting in different optical energies being output from the first output channel 31 and the second output channel 32, and realizing the beam splitting function of non-uniform beam splitting. Further, by changing the distances of the first output channel 31 and the second output channel 32 relative to the structural central axis 4, an adjustable beam splitting ratio can be achieved.

[0072] Figure 10It is the electric field distribution of a non-uniform structure optical beam splitter and the optical intensity distributions of two output ports provided in this embodiment. Since the first output channel 31 and the second output channel 32 are asymmetrically distributed with respect to the structural central axis 4, the structural symmetry of the first output channel 31 and the second output channel 32 with respect to the structural central axis 4 is broken, resulting in different optical energies output from the first output channel 31 and the second output channel 32, and realizing the beam splitting function of non-uniform beam splitting.

[0073] Figure 11 It is the one-dimensional optical intensity distribution of two output ports of a non-uniform structure optical beam splitter provided in this embodiment. The first output channel 31 is located 4 μm above the structural central axis 4, and the second output channel 32 is located 2.6 μm below the central axis 4. The beam splitting ratio of the two output channels is 0.56.

[0074] Figure 12 It is a schematic diagram of the waveguide structure of a non-uniform structure optical beam splitter provided in Embodiments 1, 2, and 3, which successively includes a loaded waveguide layer 8, a thin film lithium niobate layer 9, a buried layer 10, and a substrate layer 11 from top to bottom. The material of the loaded waveguide layer 8 is silicon nitride, which is loaded on the surface of the thin film lithium niobate layer 9 through a deposition process, with a thickness of 300 nm and a width of 1 μm, which is beneficial to restricting the fundamental modes TE0 and TM0. The thin film lithium niobate layer 9 is a slab waveguide with a thickness of 300 nm and a tangential direction of X-cut. The material of the buried layer 10 is silicon dioxide, with a thickness of 4.7 μm, and the material of the substrate 11 is silicon, with a thickness of 525 μm, which plays a supporting role.

[0075] Embodiment 4 This embodiment proposes an optical beam splitter array that realizes a Gaussian amplitude distribution, as Figure 13 shown, including an optical beam splitter 5 with uniform beam splitting and a plurality of cascaded optical beam splitters 6 with non-uniform beam splitting, which are symmetrically distributed along the array central axis 7.

[0076] The optical beam splitter array with a Gaussian amplitude distribution in this embodiment has 1 input port and 16 output ports, which is realized by cascading the optical beam splitter 4 times.

[0077] The first-order optical beam splitter is an optical beam splitter 5 with uniform beam splitting, which is used to output two beams with the same amplitude, providing a prerequisite for a centrally symmetric Gaussian amplitude distribution.

[0078] The second-order optical beam splitter is two non-uniform beam splitting optical beam splitters 6 with the same beam splitting ratio, which are respectively connected to the two output ends of the optical beam splitter 5 with uniform beam splitting in the first order.

[0079] By analogy, the fourth-order optical beam splitter has eight optical beam splitters 6 with non-uniform beam splitting. The input ends of the eight optical beam splitters 6 with non-uniform beam splitting are respectively connected to the output ends of the third-order optical beam splitter 6 with non-uniform beam splitting, and they are in one-to-one correspondence.

[0080] The eight optical beam splitters 6 with non-uniform beam splitting have 16 output ports, which are symmetrically distributed along the central axis 7. Therefore, the output Gaussian amplitude distribution is: .

[0081] As Figure 14 shown, it shows the uniform amplitude distribution and Gaussian amplitude distribution of 16 channels. The normalized amplitudes of the uniform amplitude distribution are all 1, while the amplitude at the central position of the Gaussian amplitude distribution is 1, and the amplitudes on both sides are centrosymmetrically distributed. The closer to the edge, the smaller the amplitude, and the minimum is 0.28.

[0082] As Figure 15 shown, it shows the one-dimensional near-field intensity distribution under the uniform amplitude distribution and Gaussian amplitude distribution. It can be seen from Figure 19 that the beam splitter with an energy ratio of 1:1 makes the amplitude of the output beam energy of the waveguide array present a rectangular distribution. There is an amplitude truncation at the edge part of this rectangular amplitude beam energy, that is, there is an energy value jump. The amplitude truncation phenomenon causes the far-field light wave to produce a diffraction phenomenon, resulting in a reduction in the main lobe power of the far field of the optical phased array and a reduction in the side lobe suppression ratio. The Gaussian amplitude distribution solves the amplitude truncation existing at the edge part of the array waveguide under the uniform amplitude distribution, weakens the diffraction phenomenon caused by the amplitude truncation, makes the optical energy of the waveguide array concentrate on the main lobe, and thus significantly improves the main lobe energy and side lobe suppression ratio.

[0083] As Figure 16 shown, it shows the normalized far-field distribution under the uniform amplitude distribution and Gaussian amplitude distribution. It can be seen from the figure that the maximum side lobe suppression ratio of the uniform distribution is only 13 dB, while the maximum side lobe suppression ratio of the Gaussian amplitude distribution is as high as 30 dB.

[0084] As Figure 17 shown, it shows the relationship between the non-uniform beam splitter with different beam splitting ratios and the wavelength. It can be seen from Figure 17 that the beam splitting ratio of the non-uniform beam splitter remains unchanged with the change of wavelength. The results show that the asymmetric beam splitter and its array proposed by the present invention have a bandwidth of more than 100 nm.

[0085] As Figure 18 shown, it shows the simulation results and measured results of the Gaussian amplitude distribution of 16 channels. The measured data is basically consistent with the simulation data, and the error range is small. The results show that the asymmetric beam splitter and its array proposed by the present invention have high processing tolerance and insertion loss.

[0086] As Figure 19As shown, the beam splitting ratio distributions of the beam splitters in the 8-channel beam splitter array implemented by 3-stage cascading and the 16-channel beam splitter array implemented by 4-stage cascading are shown. The results show that the beam splitting ratios of the uniform beam splitter arrays are all 0.5, while the beam splitting ratios of the beam splitters in the beam splitter array with Gaussian amplitude distribution proposed in the present invention are between 0.5 and 0.8. Among them, the beam splitting ratio of the uniform optical beam splitter (5) at the first order is 0.5, the beam splitting ratio of the optical beam splitter structure (6) cascaded at the second order is in the range of 0.5 - 0.8, the beam splitting ratio of the optical beam splitter structure (6) cascaded at the third order is in the range of 0.5 - 0.7, and the beam splitting ratios of the optical beam splitter structures (6) cascaded at the fourth order and higher orders are all less than 0.6. For several optical beam splitter structures (6) cascaded at the third order and higher orders, the beam splitting ratio of the optical beam splitter structure (6) inside the central symmetry line (7) of the array is less than that of the optical beam splitter structure (6) outside.

[0087] By breaking the structural symmetry of the multimode interference beam splitter and adopting an asymmetric multimode interference beam splitter, the present invention generates an asymmetric light intensity distribution in the multimode interference region. Further, by adjusting the asymmetric structural form of the multimode interference beam splitter, an adjustable beam splitting ratio is achieved. Compared with the asymmetric Y-branch beam splitter, the non-uniform beam splitter proposed in the present invention solves the problems of high processing difficulty and high insertion loss.

[0088] A multi-stage array cascaded with an asymmetric multimode interference beam splitter distributes the energy of a laser beam to N output ports, so that the light intensity distribution output by the waveguide array is a non-uniform amplitude distribution. This non-uniform amplitude distribution solves the amplitude truncation existing at the edge part of the array waveguide under the uniform amplitude distribution, weakens the diffraction phenomenon caused by the amplitude truncation phenomenon, and makes the optical power of the optical phased array concentrate on the main lobe, thereby significantly improving the main lobe power and the sidelobe suppression ratio.

[0089] Waveguide: A structure used to confine and guide light waves to propagate along a specific path. The working principle of a waveguide is usually based on the total reflection of electromagnetic waves at the waveguide interface.

[0090] Waveguide array: Multiple waveguides are arranged at a certain spacing.

[0091] Optical phased array: Generally composed of a beam splitter, a phase shifter and a radiator. A laser beam is divided into multiple beams by a beam splitter. After each beam is modulated by a phase shifter, it is radiated into free space by the radiator. By adjusting the phase shifter to change the phase difference of each beam, the scanning angle of the beam can be controlled.

[0092] Sidelobe: The main lobe is the region with the highest radiation intensity in the antenna pattern, usually pointing to the maximum radiation direction of the antenna. The sidelobe is other lobe outside the main lobe, with radiation intensity lower than that of the main lobe, also known as the minor lobe or side lobe. The existence of sidelobes will cause signal leakage. Therefore, when designing an antenna, it is necessary to suppress the generation of sidelobes.

[0093] Sidelobe suppression ratio: The ratio of the maximum value of the main lobe to the maximum value of the sidelobe, usually expressed in decibels (dB), is an important parameter to measure the performance of an optical phased array.

[0094] Crosstalk between adjacent waveguides: The phenomenon that the optical signal in one optical waveguide affects the optical signal in the adjacent optical waveguide due to the coupling effect of the electromagnetic field. In an optical phased array, crosstalk affects the phase calibration of the waveguide array and generates sidelobes in the far field.

[0095] Phase mismatch: The phenomenon that the phase relationship between two or more waveguide modes is not completely synchronous. This phenomenon can be used to suppress the crosstalk between adjacent waveguides.

[0096] Multimode interference effect: The phenomenon of beam splitting or merging of optical waves in different modes in an optical waveguide due to interference.

[0097] Multimode interference optical splitter: It consists of an input waveguide, a multimode interference region, and an output waveguide. After the optical field is injected into the multimode interference region through the input waveguide, constructive interference between multiple modes generates the multimode interference effect, and one or more images of the input field will be periodically generated along the propagation direction of the guided wave. Through this effect, the device can achieve power splitting of light.

[0098] Symmetric multimode interference optical splitter: It has one input waveguide, one multimode interference region, and multiple output waveguides. The multimode interference region is a vertically symmetric rectangular structure, which can divide a beam of light into multiple uniform beams of light.

[0099] 1×2 symmetric multimode interference optical splitter: It has one input waveguide, one multimode interference region, and two output waveguides. The multimode interference region is a vertically symmetric rectangular structure, which can divide a beam of light into two uniform beams of light.

[0100] Asymmetric multimode interference optical splitter: An excision operation is performed on the symmetric multimode interference region to make the multimode interference region a vertically asymmetric structure, generating an asymmetric light intensity distribution in the multimode interference region and outputting multiple beams of light with different light intensities. Further, by adjusting the asymmetric structure form of the multimode interference optical splitter, an adjustable splitting ratio can be achieved.

[0101] 1×2 asymmetric multimode interference optical splitter: Based on the asymmetric multimode interference optical splitter, there are only two output waveguides.

[0102] Beam splitting tree: Usually composed of cascaded optical beam splitters, it can split a beam of light into multiple beams of light, and these beams of light are distributed in a certain proportion in terms of energy distribution.

[0103] Uniform beam splitting tree: Composed of cascaded symmetric multimode interference optical beam splitters, it outputs beams of the same amplitude.

[0104] Non-uniform beam splitting tree: Composed of cascaded asymmetric multimode interference optical beam splitters, it outputs beams with not completely the same amplitude.

[0105] 1×N uniform beam splitting tree: Composed of multiple cascaded 1×2 symmetric multimode interference optical beam splitters connected end to end, it splits a beam of light into N beams of the same amplitude.

[0106] 1×N non-uniform beam splitting tree: Composed of multiple cascaded 1×2 asymmetric multimode interference optical beam splitters connected end to end, it distributes a beam of light to N output ports in a certain proportion. The amplitude distribution of the N output ports is determined by the beam splitting ratios and the cascading order of the cascaded multiple 1×2 optical beam splitters with adjustable beam splitting ratios.

[0107] Amplitude distribution: Along the direction of the waveguide array, it is the form of the output optical energy distribution of the waveguide array.

[0108] Uniform amplitude distribution: Along the direction of the waveguide array, the output optical energy of the waveguide array is the same.

[0109] Gaussian amplitude distribution: Along the direction of the waveguide array, the output optical energy distribution of the waveguide array presents a Gaussian-type amplitude distribution.

[0110] The above embodiments are used to explain the present invention, rather than limit the present invention. Any modification and change made within the spirit and protection scope of the claims of the present invention fall within the protection scope of the present invention.

Claims

1. An optical beam splitter structure, characterized in that, It includes a beam splitter body which includes an input channel (1), a power distribution area (2), and an output channel (3) connected in sequence. The input channel (1), the power distribution area (2), and the output channel (3) are arranged along the central axis (4); the beam splitter body is asymmetrically arranged with respect to the central axis (4), and the output channel (3) includes a first output channel (31) and a second output channel (32).

2. The optical splitter structure according to claim 1, wherein Among the input channel (1), the power distribution area (2), and the output channel (3), only two of them are symmetrically arranged with respect to the central axis (4) at the same time.

3. The optical splitter structure according to claim 1 or 2, characterized in that The power distribution area (2) includes a third area (23), and on the upper and lower sides of one end of the third area (23) close to the input channel (1) are a first area (21) and a second area (22) respectively.

4. The optical splitter structure according to claim 3, wherein, The cross-sectional area shapes of the first area (21) and the second area (22) are rectangle, square, triangle, trapezoid or circle.

5. The optical beam splitter structure according to claim 4, wherein, The cross-sectional areas of the first area (21) and the second area (22) are different. The input channel (1) is symmetrically arranged with respect to the central axis (4), and the first output channel (31) and the second output channel (32) are symmetrically distributed with respect to the central axis (4).

6. The optical splitter structure according to claim 3, characterized in that The cross-sectional areas of the first area (21) and the second area (22) are equal, and the third area (23) is symmetrically arranged along the central axis (4); when the input channel (1) is symmetrically arranged with respect to the central axis (4), the first output channel (31) and the second output channel (32) are asymmetrically arranged with respect to the central axis (4); when the input channel (1) is asymmetrically arranged with respect to the central axis (4), the first output channel (31) and the second output channel (32) are symmetrically arranged with respect to the central axis (4).

7. An optical beam splitter structure array, characterized in that, It includes a light beam splitter (5) for uniform beam splitting, a first beam splitter array (601), and a second beam splitter array (602); the first-order beam splitter is the light beam splitter (5) for uniform beam splitting. The first beam splitter array (601) and the second beam splitter array (602) are respectively cascaded at the output end of the light beam splitter (5) for uniform beam splitting, and the first beam splitter array (601) and the second beam splitter array (602) are symmetric with respect to the array center symmetry line (7).

8. The beam splitter structure array according to claim 7, characterized in that, The first beam splitter array (601) and the second beam splitter array (602) are the same. The first beam splitter array (601) is formed by cascading a plurality of beam splitter structures (6) described in claim 1 end to end.

9. A beam splitter structure array according to claim 8, wherein, The first beam splitter array (601) includes a second-order cascaded beam splitter structure (6010). The output end of the second-order cascaded beam splitter structure (6010) is cascaded with a third-order cascaded beam splitter structure (6020), and the output end of the third-order cascaded beam splitter structure (6020) is sequentially cascaded with a plurality of beam splitter structures.

10. A beam splitter structure array according to claim 9, characterized in that, The beam splitting ratio of the beam splitter (5) with uniform beam splitting at the first stage is 0.

5. The beam splitting ratio of the cascaded beam splitter structure (6010) at the second stage is in the range of 0.5 - 0.

8. The beam splitting ratio of the cascaded beam splitter structure (6020) at the third stage is in the range of 0.5 - 0.7, and the beam splitting ratio of the beam splitter structure closer to the central symmetry line (7) is less than that of the beam splitter structure farther from the central symmetry line (7); the beam splitting ratios of the beam splitter structures connected to the rear end of the cascaded beam splitter structure (6020) at the third stage are all less than 0.6.

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