A 1×N arbitrary splitting ratio optical splitter and method

Abstract

The present invention discloses a 1×N arbitrary splitting ratio optical splitter and method. The optical splitter includes an input waveguide, a first-stage tapered waveguide, a second-stage tapered waveguide, a string-shaped waveguide, an array of receiving waveguides of varying widths, a gradient depth region, an oblique straight waveguide, a bend-compensating waveguide, an auxiliary waveguide, and a straight waveguide. The present invention not only enables all channels to output light with the same energy, but also enables arbitrary light output shapes by adjusting the length and width of the first-stage and second-stage tapered waveguides, as well as the width of the array of tapered receiving waveguides. The structure of the present invention can rapidly increase the number of output channels while maintaining the miniaturization of the overall chip. The introduction of the gradient depth region and edge auxiliary waveguides helps reduce the chip's insertion loss. Furthermore, by adopting a method of dividing the light distribution for stable transmission, the light intensity fluctuations output from each channel of the optical splitter can be kept very small within a large bandwidth.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical splitters, and in particular relates to a broadband, low-loss 1×N arbitrary splitting ratio optical splitter and a method for realizing arbitrary shape light output by using the optical splitter. Background Art

[0002] Optical splitters are essential passive optical components in the rapid development of optical communications. As one of the core components of passive optical fiber networks, they evenly distribute signals to users, making them key to achieving the "last mile" between the network and users. They are widely used in optical communication systems, fiber-optic user networks, passive optical networks (PONs), optical local area networks, and other fields. They are also one of the fundamental functional components for building high-density integrated chips and are widely used in complex photonic systems such as optical switches, wavelength division multiplexing, optical phased arrays, orbital angular momentum light generation, and quantum computing.

[0003] Currently, multichannel optical splitters are primarily fabricated using planar waveguide technology, with three main approaches: cascaded 1×2, MMI multimode interference, and star coupler. The main challenges with cascaded approaches are their large size and relatively complex design. To achieve the desired optical output, each stage requires careful structural design, and the optical splitting error of the previous stage directly affects the optical output of the next stage. While this approach maintains the excellent performance of the cascaded unit, the device size, loss, and design complexity are proportional to the number of output channels. MMI multimode interference achieves multi-channel output through a larger interference region. This approach is widely used to construct complex photonic networks with a limited number of output channels. However, since the number of output channels is proportional to the size of the interference imaging region, achieving a larger number of channels (N>16) results in a bulky device, making it unsuitable for high-density integration. A third approach utilizes a star coupler, utilizing arrayed waveguides to couple light through the free propagation region (FPR) to achieve multi-channel output. The advantage is that when the number of outputs increases significantly, the size of the device does not increase significantly, but the output light energy distribution is usually Gaussian, making it difficult to achieve equal energy in all channels.

[0004] In addition, compared with traditional equal-power dividers, different types of optical power distribution are more suitable for optical systems in certain specific environments, such as in optical feedback systems, nonlinear conversion, quantum computing, or optical signal processing. Therefore, it is very important to be able to design a simple, integrated splitter with diversified outputs. Summary of the Invention

[0005] The purpose of the present invention is to provide a 1×N arbitrary splitting ratio splitter with large bandwidth and low loss, and a method for using the splitter to achieve arbitrary shape light output. While ensuring a compact structure, it solves problems such as high insertion loss and small operating bandwidth. It can also design the required output end light energy distribution according to different needs, laying the foundation for the design of future high-density integrated complex photonic chip systems.

[0006] The technical solution to achieve the above purpose is:

[0007] A 1×N arbitrary splitting ratio optical splitter comprises an input waveguide, a first-stage tapered waveguide, a second-stage tapered waveguide, a chordal waveguide, an array of receiving waveguides of different widths, an oblique straight waveguide, a bend-compensating waveguide, and a straight waveguide. The input waveguide, first-stage tapered waveguide, second-stage tapered waveguide, chordal waveguide, array of receiving waveguides of different widths, an oblique straight waveguide, a bend-compensating waveguide, and a straight waveguide are sequentially connected. The chordal waveguide is used to match the angle of light output from the end of the second-stage tapered waveguide. The bend-compensating waveguide is used to adjust the spacing between channels. A rectangular or other type of light output can be obtained by adjusting the initial width and length, as well as the end width and length, of the first-stage tapered waveguide and the second-stage tapered waveguide. Uniform energy splitting or other types of splitting can be achieved by adjusting the width of the waveguides in the array of receiving waveguides of different widths to split the rectangularly distributed light.

[0008] Furthermore, the first-stage tapered waveguide and the second-stage tapered waveguide are designed asymmetrically to adjust the incident direction of the input light, and are coupled with receiving waveguide arrays of different widths for light splitting, thereby achieving any type of light output with low loss and large bandwidth.

[0009] Furthermore, the angle between the light beam in the second-stage tapered waveguide and the normal line of the side boundary is larger than the angle between the light beam in the conventional MMI structure and the normal line of the side boundary.

[0010] Furthermore, the string-shaped waveguide is connected to the end of the second-stage tapered waveguide, centered at the starting point of the triangle corresponding to the second-stage tapered waveguide. The radius of the corresponding circle is: sqrt((L2+L_ref)^2+Wot3^2 / 4), where L2 is the length of the second-stage tapered waveguide, L_ref is the length required to extend the second-stage tapered waveguide into a triangle, and Wot3 is the width of the end of the second-stage tapered waveguide. This second-stage tapered waveguide can not only achieve a stable rectangular light distribution, but also, by appropriately adjusting the structural parameters, various other types of light distributions, such as single-peak, double-peak, and multi-peak. By coupling and splitting the light using an array of receiving waveguides of the same length and different widths, any type of light output can be achieved.

[0011] Furthermore, the array of receiving waveguides with different widths is composed of a series of tapered waveguides with different widths and the same length.

[0012] Furthermore, it also includes a gradient depth zone, which is connected to the end of the string-shaped waveguide along a circular curve with the receiving waveguide arrays of different widths, so that the mode field of the light after passing through the second-stage tapered waveguide is gradient when it is transmitted in the receiving waveguide arrays of different widths.

[0013] Furthermore, an auxiliary waveguide is included, which is used to collect edge energy of the output light of the second-stage tapered waveguide, so that the collected light is directly sent to the adjacent channel.

[0014] Furthermore, after achieving stable transmission of light in the second-stage tapered waveguide by adjusting the structure, the ratio of the end width to the length is kept unchanged without changing the initial width of the second-stage tapered waveguide. By changing the size of the second-stage tapered waveguide, a similar light distribution can still be obtained, which helps to obtain output with more channels.

[0015] The method for realizing arbitrary-shape light output using the 1×N arbitrary-splitting-ratio optical splitter comprises:

[0016] Step (1): If the desired light output is symmetrically distributed, the first-stage tapered waveguide is set to a symmetrical structure to reduce the divergence angle of the incident light; if the desired light output is asymmetrically distributed, the offset of the end of the first-stage tapered waveguide relative to the symmetry center is adjusted to gradually adjust the incident direction of the input light to achieve asymmetric adjustment;

[0017] Step (2): The second-stage tapered waveguide is arranged to have the same center of symmetry as the first-stage tapered waveguide, and the length, width, and symmetry of the second-stage tapered waveguide are adjusted to achieve stable transmission of light in the structure. The stable transmission of light in the structure is an important factor in achieving stable output of any type of light under a large bandwidth.

[0018] Step (3): Setting the length of the string-shaped waveguide to match the width of the end of the second-stage tapered waveguide, integrating the envelope of the output light using an algorithm, and calculating the different widths of the corresponding receiving waveguides based on the required light intensity distribution; arranging an array of tapered receiving waveguides of the same length and different widths along the end of the string-shaped waveguide, with each receiving waveguide extending through the center of the circle corresponding to the string-shaped waveguide, thereby coupling the stable light distribution in step (2) and dividing the light of different intensities into N channels;

[0019] Step (4): Use a combination of an oblique straight waveguide and a bending compensation waveguide with different radii to achieve waveguide equidistant output.

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

[0021] The present invention can change the output end light energy distribution by adjusting the length and width of the first and second tapered waveguides and the width of the tapered receiving waveguide array, thereby realizing light output of the same or different energy in the channels. Compared with the cascade type and multi-mode interference type splitting solutions, it not only greatly reduces the size of the overall chip and simplifies the design, but also can realize diversified light output under large channels. The auxiliary waveguides and gradient depth zones introduced at the edge are conducive to reducing the additional loss and coupling loss of the chip, so that the insertion loss of the overall chip is very small. In addition, the structure can stably maintain an approximately rectangular distribution or other types of distribution before splitting, so that the light energy fluctuation of each channel of the device can be kept at a low value within a large bandwidth. From a process point of view, the splitter structure of the present invention can utilize the processing technology of the wavelength division multiplexing device AWG widely used in communications, without adding other difficulties in the middle, and is more suitable for technology migration and large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of a 1×N arbitrary splitting ratio type optical splitter and a schematic diagram of a variable splitting ratio component;

[0023] Figure 2 This is the simulation structure diagram of 1×16 with the same output energy;

[0024] Figure 3 This is the simulation structure diagram of the 1×16 output energy curve distribution;

[0025] Figure 4 This is the result diagram of 1×16 output with the same energy and other energy distribution outputs;

[0026] Figure 5 This is a simulation structure diagram of 1×64 with the same output energy;

[0027] Figure 6 This is the output result diagram of the simulation structure with the same 1×64 output energy;

[0028] Figure 7 This is a graph showing how the output results of four randomly selected channels in a 1×64 structure vary with wavelength.

[0029] Markings in the figure: 1-input waveguide; 2-first-stage tapered waveguide; 3-second-stage tapered waveguide; 4-chord waveguide; 5-receiving waveguide array with different widths; 6-gradual depth zone; 7-slanted straight waveguide; 8-bend compensation waveguide; 9-auxiliary waveguide; 10-straight waveguide. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings. This embodiment is applicable to the design of a photonic device with N channels (N≥2, where N is a positive integer).

[0031] See also Figure 1-7 The 1×N arbitrary splitting ratio optical splitter of this embodiment includes an input waveguide 1, a first-stage tapered waveguide 2, a second-stage tapered waveguide 3, a chordal waveguide 4, a receiving waveguide array 5 of varying widths, a slanted straight waveguide 7, a bend-compensating waveguide 8, and a straight waveguide 10, all connected in sequence. Furthermore, to reduce excess chip loss and coupling loss, the optical splitter also includes an auxiliary waveguide 9 and a gradient depth region 6. In this embodiment, the gradient depth region 6 and the receiving waveguide array 5 of varying widths are connected to the end of the chordal waveguide 4 along a circular curve. The receiving waveguide array 5 of varying widths is composed of a series of tapered waveguides of varying widths but the same length.

[0032] In this embodiment, the optical splitter structure is designed using lithium niobate thin film material with a core refractive index of 2.21 and a cladding refractive index of 1.4431. The single-mode rectangular waveguide has dimensions of 1μm × 250nm. The optical splitter structure and waveguide dimensions can also be designed based on other materials, and this is only an example. The initial width of the first-stage tapered waveguide is consistent with the width of the single-mode waveguide, with a terminal width Wot1 of 2.55μm and a length L1 of 5μm. The second-stage tapered waveguide has an initial width Wot2 of 5μm, a terminal width Wot3 of 30μm, and a length L2 of 60μm. The string waveguide is centered at the starting point O where the second-stage tapered waveguide extends into a triangle, and is connected to the end of the second-stage tapered waveguide. The radius is: sqrt((L2+L_ref)^2+Wot3^2 / 4), where L2 is the length of the second-stage tapered waveguide, L_ref is the length of the second-stage tapered waveguide extended into a triangle, and Wot3 is the width of the end of the second-stage tapered waveguide. The structure is as follows: Figure 1 shown.

[0033] In particular, the first-stage tapered waveguide 2 is often used in photonic devices to reduce the divergence angle of the light beam and lower the insertion loss of the device. The present invention retains this function while using it as an important structure to achieve the change of output end light energy.

[0034] Compared with conventional MMI multimode interference devices, the second-stage tapered waveguide 3 increases the angle between the light beam and the normal of the side boundary after passing through the first-stage tapered waveguide 2; according to the Fresnel reflection law, when light is emitted from a denser medium to a less dense medium, when the critical angle (total reflection angle) is reached, the light will undergo total reflection at the interface; therefore, compared with conventional MMI multimode interference devices, the second-stage tapered waveguide 3 in the present invention increases the incident angle of the light beam at the side boundary, thereby increasing the proportion of the light beam that is totally reflected at the side boundary after transmitting through the first tapered waveguide, reducing the transmission loss of the light beam transmitted to the boundary, thereby further reducing the additional loss of the device.

[0035] In particular, the present invention combines the first-stage tapered waveguide 2 and the second-stage tapered waveguide 3, further reducing the device's insertion loss while also serving as a crucial component in achieving the primary function of the entire optical splitter. By adjusting the lengths and initial and terminal widths of the first-stage and second-stage tapered waveguides, various light distribution types can be achieved at the terminal end of the second-stage tapered waveguide. Importantly, by appropriately adjusting these parameters, a nearly rectangular light distribution can be achieved. This rectangular light distribution is caused by multimode interference. Furthermore, while maintaining the first-stage parameters and the initial width of the second-stage tapered waveguide unchanged, proportionally increasing the length and terminal width of the second-stage tapered waveguide can maintain this rectangular light distribution. This approach is crucial for implementing optical splitters with the same energy output and can also be implemented with processing equipment of varying precision. Of course, in addition to maintaining a rectangular light distribution, other types of light distributions can also be achieved through the aforementioned adjustment method. The first-stage and second-stage tapered waveguides can be symmetrical or asymmetrical, and their shapes are not limited to linear tapered waveguides.

[0036] In particular, the first-stage tapered waveguide can adjust the incident angle of the input light in the second-stage tapered waveguide through an asymmetric design, thereby obtaining a stable asymmetric light distribution after transmission through the second-stage tapered waveguide.

[0037] In particular, the second-stage tapered waveguide can not only obtain a rectangular light distribution, but also, after appropriate parameter adjustment, can obtain other types of light distributions such as single-peak, double-peak, and multi-peak. By coupling and splitting the light using receiving waveguide arrays of different widths, any type of light output can be achieved with low loss and large bandwidth.

[0038] In particular, because the divergence angle of light in the first-order and second-order tapered waveguides is related to the refractive index difference, the larger the divergence angle, the smaller the size required to form a stable rectangular light distribution in the first-order and second-order tapered waveguides. Therefore, the structure of the present invention is more conducive to achieving a small size compared to high-refractive-index materials.

[0039] The string-shaped waveguide 4 is designed to match the special angle of the output light at the end of the second-stage tapered waveguide 3, reduce the coupling loss between the mode fields at the connection with the receiving waveguide array 5 of different widths and the loss of mutual conversion between modes in the tapered waveguide, and facilitate the design of spectral chips such as the calculation of phase difference.

[0040] The array of receiving waveguides 5 with varying widths divides the rectangularly distributed light envelope by adjusting the widths of the receiving waveguides in different channels, thereby varying the coupling strength of the rectangular light distribution output, thereby achieving multi-channel light output with the same energy. To reduce mode conversion losses in the tapered waveguides and ensure that the overall device loss does not increase dramatically, the minimum length of the tapered waveguides used for the receiving waveguides in the different channels must be sufficient to ensure that the approximate condition of adiabatic gradual variation is met during light transmission. Because the light envelope output from the end of the second-stage tapered waveguide is rectangular, a large portion of the receiving waveguides in the array of receiving waveguides with varying widths have approximately the same width. Based on the aforementioned second-stage tapered waveguides, they can be scaled up proportionally. Therefore, to achieve more channel output, it is only necessary to ensure that the minimum width of the central channel receiving waveguide approximates that of a single-mode waveguide. This allows for structural design while maintaining a very small size, laying the foundation for integrated operation. Compared to Y-branch cascade and multimode interference-based solutions for achieving multi-channel output, the structure of the present invention can achieve the same amount of light output in a smaller size.

[0041] Compared with the design of a multi-channel splitter using a Rowland circle and waveguide arrays of different widths in an arrayed waveguide grating, the present invention can achieve the same energy output for all channels while ensuring a smaller size and low loss. The Rowland circle structure uses the diffraction envelope of light to split. The light envelope before splitting is Gaussian, resulting in strong energy in the central channel and too low energy in the edge channels, making it difficult to achieve the same energy in all channels. At the same time, since the width of the central waveguide is too small, the coupling between the mode fields near the central channel will be very serious.

[0042] The gradient depth region 6 is designed to ensure that the mode field of the light after passing through the second-stage tapered waveguide is gradually changed when it is transmitted in the receiving waveguide array of different widths. This method can make the light distribution output by the second-stage tapered waveguide more closely match the light mode of the waveguide array of different widths at the rear end. In addition, since the etching depth between different channels is gradually changed, it can be ensured that the light can gradually transition to the waveguide array, realizing low-loss optical transmission.

[0043] The bending compensation waveguide 8 is used to adjust the spacing between the channels. The bending radius of different channels is designed according to the size of the spacing between the output straight waveguides. It should be noted that the minimum bending radius is required to ensure that there is no loss when light is transmitted in the waveguide.

[0044] In particular, the loss-reducing auxiliary waveguide 9 is designed to collect the edge energy of the light output by the second-stage tapered waveguide. After being regulated by the second-stage tapered waveguide, the rectangular light envelope still retains some weak energy at the edges. Therefore, light collection can be achieved by adding two waveguides with adjustable widths to the aforementioned arrayed waveguides of varying widths. The collected light is then directly fed into adjacent channels via a bend-compensating waveguide, thereby reducing overall chip loss. It is important to note that to prevent energy loss due to destructive interference between the light collected by the auxiliary waveguide and the light from adjacent waveguides, the bending radius and overall length of the auxiliary waveguide must be precisely designed, carefully considering factors such as the effective refractive index of waveguides of varying widths and the coupling of different modes that affect phase changes.

[0045] Figure 2-4 The structure and energy output of the 1×16 arbitrary splitting ratio optical splitter are shown; Figure 5-7 The structure and energy output of the 1×64 arbitrary splitting ratio splitter are shown.

[0046] By adjusting the length and width of the first and second tapered waveguides in the optical splitter of the present invention and the width of the tapered receiving waveguide array, the output light energy distribution can be changed to achieve light output of the same or different energy in the channels; compared with the cascade type and the multi-mode interference coupling followed by splitting scheme, the optical splitter of the present invention not only greatly reduces the size of the overall chip and simplifies the design, but also can achieve output energy adjustment of multiple channels; the auxiliary waveguides and gradient depth zones introduced at the edge are conducive to reducing the additional loss and coupling loss of the chip, making the insertion loss of the overall chip very small; in addition, due to the use of a rectangular light distribution method for cutting stable transmission, the channels of the evenly classified device can maintain good uniformity within a large bandwidth; from a process point of view, the optical splitter structure of the present invention can use the processing technology of the wavelength division multiplexing device AWG widely used in communications, without adding other difficulties in the middle, and is more suitable for technology migration and large-scale production.

[0047] The above is merely an illustration of the embodiments of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A 1×N arbitrary splitting ratio type optical splitter, characterized in that: The invention comprises an input waveguide, a first-stage tapered waveguide, a second-stage tapered waveguide, a string-shaped waveguide, an array of receiving waveguides of different widths, an oblique straight waveguide, a bending compensation waveguide, a straight waveguide, and a gradient depth zone; wherein the input waveguide, the first-stage tapered waveguide, the second-stage tapered waveguide, the string-shaped waveguide, an array of receiving waveguides of different widths, an oblique straight waveguide, a bending compensation waveguide, and a straight waveguide are connected in sequence, the string-shaped waveguide is used to match the angle of the output light at the end of the second-stage tapered waveguide, the bending compensation waveguide is used to adjust the interval between each channel, and the channel is connected to the first-stage tapered waveguide, the second-stage tapered waveguide, the string-shaped waveguide, an array of receiving waveguides of different widths, an oblique straight waveguide, a bending compensation waveguide, and a straight waveguide. By adjusting the initial width and length as well as the terminal width and length of the first-stage tapered waveguide and the second-stage tapered waveguide, a rectangular distribution or other types of distribution of light output can be obtained. By adjusting the width of the waveguides in the receiving waveguide arrays of different widths, the light of the rectangular distribution is divided to obtain the same energy splitting or other types of splitting. The gradient depth region and the receiving waveguide arrays of different widths are connected to the end of the string-shaped waveguide along a circular curve, so that the mode field of the light after passing through the second-stage tapered waveguide is gradually changed when it is transmitted in the receiving waveguide arrays of different widths.

2. The 1×N arbitrary splitting ratio type optical splitter according to claim 1, characterized in that: The first-stage tapered waveguide and the second-stage tapered waveguide are designed asymmetrically to adjust the incident direction of the input light, and are coupled with receiving waveguide arrays of different widths for light splitting, thereby achieving any type of light output with low loss and large bandwidth.

3. The 1×N arbitrary splitting ratio type optical splitter according to claim 1, characterized in that: The system also includes an auxiliary waveguide, which is used to collect edge energy of the output light of the second-stage tapered waveguide, so that the collected light is directly sent into the adjacent channel.

4. The 1×N arbitrary splitting ratio type optical splitter according to claim 1, characterized in that: The receiving waveguide array with different widths is composed of a series of tapered waveguides with different widths and the same length.

5. The 1×N arbitrary splitting ratio type optical splitter according to claim 1, characterized in that: The string-shaped waveguide is connected to the end of the second-stage tapered waveguide with the starting point of the triangle corresponding to the second-stage tapered waveguide as the center of the circle; the corresponding circle radius is: sqrt((L2+L_ref)^2+Wot3^2 / 4), where L2 is the length of the second-stage tapered waveguide, L_ref is the length required for the second-stage tapered waveguide to extend into a triangle, and Wot3 is the width of the end of the second-stage tapered waveguide.

6. The 1×N arbitrary splitting ratio type optical splitter according to claim 1, characterized in that: After achieving stable transmission of light in the second-stage tapered waveguide by adjusting the structure, the ratio of the end width to the length is kept unchanged without changing the initial width of the second-stage tapered waveguide. By changing the size of the second-stage tapered waveguide, a similar light distribution can still be obtained, and more channels of output can be obtained.

7. The method for realizing arbitrary shape light output by the 1×N arbitrary splitting ratio type spectrometer according to any one of claims 1 to 6, characterized in that: include: Step (1): If the desired light output is symmetrically distributed, the first-stage tapered waveguide is set to a symmetrical structure to reduce the divergence angle of the incident light; if the desired light output is asymmetrically distributed, the offset of the first-stage tapered waveguide relative to the symmetry center is adjusted to gradually adjust the incident direction of the input light to achieve asymmetrical adjustment; Step (2): Set the symmetry center of the second-stage tapered waveguide to be the same as that of the first-stage tapered waveguide, and adjust the length, width and symmetry of the second-stage tapered waveguide to achieve stable transmission of light in the structure; Step (3): Set the length of the string waveguide to match the width of the end of the second-stage tapered waveguide, integrate the envelope of the output light using an algorithm, and calculate the different widths of the corresponding receiving waveguides based on the required light intensity distribution; arrange an array of tapered receiving waveguides of the same length and different widths along the end of the string waveguide, and each receiving waveguide passes through the center of the circle corresponding to the string waveguide after extension, that is, couple the stable light distribution in step (2) and divide the light of different intensities into N channels; Step (4): Use a combination of oblique straight waveguides and bend compensation waveguides with different radii to achieve waveguide equidistant output.

Images