Optical phase change material-based optical power divider with power division ratio capable of being adjusted in large range

Abstract

The invention discloses an optical phase-change material-based optical power divider with a power division ratio adjustable in a large range, which sequentially comprises a substrate layer, an oxide layer, a silicon core layer and a phase-change material layer from bottom to top, and is characterized in that a device structure written by the phase-change material layer comprises an input waveguide, a multimode interference region and an output waveguide, the multimode interference area comprises an asymmetric structure and a sub-wavelength grating structure, the input waveguide is connected with the multimode interference area through a conical structure, the sub-wavelength grating structure is added to the tail end of the multimode interference area, and the multimode interference area is connected with the output waveguide through the conical structure. According to the invention, the material in the surface phase-change material layer is converted from a crystalline state to an amorphous state by using external laser, so that the asymmetry of the structure of the multimode interference region is realized, and the optical power ratios of the two output ports are regulated and controlled to be different. When the laser changes the length of the phase change area, the power distribution ratio of the output port can be correspondingly changed, and therefore large-range power adjustment is achieved.

Description

Technical Field

[0001] This invention belongs to the field of integrated photonics technology, specifically relating to an optical power divider with a wide range of adjustable power ratio based on optical phase change materials. Background Technology

[0002] Optical power dividers based on multi-mode interference (MMI) coupling structures are widely used in optical communication and photonic integrated circuits for power distribution of optical signals due to their simple structure, low insertion loss, and large fabrication tolerance. However, in traditional optical communication or photonic chip systems, commonly used optical power dividers can only achieve a fixed power division ratio; once the device is fabricated, its function is determined and cannot be changed. Currently, the rapid development of fields such as optical computing, artificial neural networks, and reconfigurable photonic integrated circuits has placed new demands on on-chip optical device circuits, such as multifunctionality, reconfigurability, and flexible configuration, which traditional optical waveguide devices struggle to meet.

[0003] In recent years, phase change materials (PCMs) have become a research hotspot in photonic integrated circuits due to their non-volatility, high refractive index contrast, and reversible phase transition properties. The core characteristic of PCMs stems from the reversible conversion between a crystalline state (ordered lattice, high refractive index) and an amorphous state (disordered arrangement, low refractive index). Sb₂Se₃, as an optical PCM with extremely low loss in the optical communication band, possesses significant research and application value in photonic integrated devices due to its excellent refractive index tunability and low loss characteristics. Furthermore, the refractive index of this material is close to that of silicon, allowing PCM patches to be directly integrated on standard silicon-on-insulator (SOI) photonic platforms.

[0004] Existing research employs a thermo-optical modulation scheme to achieve adjustable power division ratios: by altering the local refractive index outside the MMI region using thermo-optical effects, power regulation is achieved. While this scheme offers the advantage of low loss, the power division ratio of a single device is unique and the adjustable range is extremely small. Adjustment power consumption is high, and the function is volatile, requiring multiple devices to cover a wider power division ratio range. Therefore, how to utilize phase change materials to realize an optical power divider with a large adjustable range, low power consumption, and non-volatile function is currently a research focus, and has significant practical implications for promoting the development of neural networks, optical computing, and other fields. Summary of the Invention

[0005] Technical problem to be solved: In view of the above-mentioned technical problems, the present invention provides an optical power divider with a wide range of adjustable power ratio based on optical phase change materials. It aims to utilize the characteristics of phase change materials to realize an adjustable optical power divider with a wide adjustable range, low power consumption and non-volatile function.

[0006] Technical solution: An optical power divider with a wide range of adjustable power ratio based on optical phase change materials, comprising, from bottom to top, a substrate layer, an oxide layer, a silicon core layer, and a phase change material layer. The device structure written in the phase change material layer includes an input waveguide, a multimode interference region, and an output waveguide. The multimode interference region includes an asymmetric structure and a subwavelength grating structure. The input waveguide is connected to the multimode interference region through a tapered structure. A subwavelength grating structure is added at the end of the multimode interference region and connected to the output waveguide through the tapered structure.

[0007] Preferably, the asymmetric structure is trapezoidal, and the phase change material within the asymmetric structure changes from a crystalline state to an amorphous state.

[0008] Preferably, the phase change material layer is deposited on the upper surface of the silicon core layer.

[0009] Preferably, the input waveguide is connected to the multimode interference region via a tapered structure, and the output waveguides at both ends are connected to the multimode interference region via tapered structures.

[0010] Preferably, the height of the substrate layer is 500 μm, the height of the oxide layer is 2 μm, the height of the silicon core layer is 0.22 μm, and the height of the phase change material layer is 0.05 μm; the width of the input waveguide and the length of the output waveguide are 1.2 μm and 5 μm respectively.

[0011] Preferably, the width of the multimode interference region is 5 μm and the length is 28 μm.

[0012] Preferably, the arbitrary power division ratio of the optical power divider is achieved by changing the size of the asymmetric structure in the multimode interference region, and the length adjustment range of the asymmetric structure is 0-25μm.

[0013] Beneficial effects: 1) Compared with traditional optical power dividers, the power ratio adjustment range of the present invention is significantly expanded, and the device can be repeatedly reconfigured after fabrication; 2) The phase change material is non-volatile, the phase state is stable and does not drift over time, and the set power ratio can be maintained for a long time in a power-free state; 3) The device is easy to manufacture and the process is simple, which is conducive to large-scale mass production; 4) The power ratio adjustment operation is simple, the main structure of the multimode interference region remains unchanged, and the power ratio can be controlled by only performing phase state conversion on the phase change material in a specific region. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of an optical power divider with a wide range of adjustable power ratio based on optical phase change materials in an embodiment of the present invention, wherein the shaded area is the region of amorphous phase change material; Figure 2 This is a schematic diagram of an existing optical power divider; Figure 3 This is a schematic diagram of the cross-section at the connection between the input waveguide and the multimode interference region; Figure 4 This is a schematic diagram of the cross-section at the connection between the multimode interference region and the output waveguide; Figure 5 The diagram shows the electric field evolution under power distribution ratios of 40:60, 30:70, 20:80, and 10:90 implemented by the optical power divider of this invention. Figure 6 This invention relates the output optical power distribution ratio between the upper and lower ends of the optical power divider to the length of the laser phase transition region. In the figure, the numbers are: 101, input waveguide; 102, multimode interference region; 102-a, asymmetric structure; 102-b, subwavelength grating structure; 103, output waveguide. Detailed Implementation

[0015] The present invention will be described in detail below with reference to specific embodiments: Figure 2 The diagram shows an existing optical power divider, including an input waveguide, a multimode interference region, and an output waveguide. Due to structural symmetry, this device can only uniformly distribute the input optical power to the two output ports, failing to meet the increasing flexibility requirements of current photonic integration technology. Therefore, to achieve flexible adjustment of the output optical power distribution ratio, this invention proposes... Figure 1 The device structure shown is based on a non-volatile phase change material. It utilizes the refractive index difference between the crystalline and amorphous states of the phase change material to construct an optical waveguide structure and further designs... Figure 1 The asymmetric optical power divider structure shown disrupts the structural symmetry of the multimode interference region by introducing an asymmetric structure into a typical multimode interference-coupled optical power divider. This results in unequal optical power at the two output waveguide ports, and the greater the disruption of structural symmetry, the greater the difference in optical power between the two output ports. Therefore, the output power division ratio of the device can be adjusted by using laser phase-change technology to change the size of the asymmetric structural region. Example 1

[0016] This invention provides an optical power divider with a wide range of adjustable power ratio based on optical phase change materials. See [link to relevant documentation]. Figure 3 and Figure 4 The device structure, from bottom to top, includes a substrate layer, an oxide layer, a silicon core layer, and a phase change material layer. The device structure written in the phase change material layer includes an input waveguide 101, a multimode interference region 102, and an output waveguide 103. The multimode interference region 102 includes an asymmetric structure 102-a and a subwavelength grating structure 102-b. The phase change material in the asymmetric structure 102-a region is in an amorphous state. The subwavelength grating structure 102-b is used to reduce the mode interference length of the multimode interference region, which is beneficial to reducing the overall size of the device.

[0017] The aforementioned phase change material layer is deposited on the upper surface of the silicon core layer.

[0018] The operation to achieve non-uniform port power output involves altering the state of the phase change material in a portion of the multimode interference region to prepare an asymmetric structure 102-a. This region is trapezoidal, and the phase change material within it transitions from a crystalline to an amorphous state. The optical power divider achieves wide-range power ratio control by changing the size of this trapezoidal region, which has an adjustable length range of 0-25 μm.

[0019] The input waveguide 101 is connected to the multimode interference region 102 through a tapered structure, and the output waveguides 103 at both ends are connected to the multimode interference region 102 through a tapered structure.

[0020] The height of the substrate layer is 500 μm, the height of the oxide layer is 2 μm, the height of the silicon core layer is 0.22 μm, and the height of the phase change material layer is 0.05 μm; the width of the input waveguide 101 and the length of the output waveguide 103 are 1.2 μm and 5 μm respectively.

[0021] The trapezoidal length of the input waveguide 101 connected to the multimode interference region 102 is 9.9 μm, the upper base width is 1.2 μm, and the lower base width is 3 μm; the trapezoidal length of the output waveguide 103 connected to the multimode interference region 102 is 13.2 μm, the upper base width is 1.2 μm, and the lower base width is 2.1 μm.

[0022] Figure 5 Figures (a)-(d) show the electric field evolution diagrams of the power division ratios achieved by the optical power divider of the present invention under different asymmetric structural region lengths: 40:60, 30:70, 20:80, and 10:90. The calculation method is the finite difference time domain method (FDTD), and the specific material and structural parameters are as follows: A 50 nm thick layer of phase change material Sb₂Se₃ is deposited on a standard SOI (silicon-on-insulator, SOI) wafer by magnetron sputtering. In addition, to prevent oxidation of the phase change material, an additional 20 nm thick silicon dioxide protective layer is deposited. The input and output waveguides of the device are both 1.2 μm wide, the multimode interference region is 5 μm wide and 28 μm long, the subwavelength grating structure is 6 μm long, the gap between the output waveguides is 0.8 μm, the subwavelength grating period is 600 nm, and the grating duty cycle is 0.5. Example 2

[0023] Embodiment 1 of the present invention provides an optical power divider with a wide range of adjustable power ratio based on optical phase change materials, through the fabrication of... Figure 1The symmetry of the multimode interference region 102 is disrupted by using the asymmetric structure 102-a portion of the multimode interference region 102 shown, resulting in the structure shown. Here, Lr is the length of the altered region. Figure 1 In the middle, Lr = 10μm, the upper base width of the trapezoidal structure is 1μm and the lower base width is 1.3μm; Figure 5 The diagram shows the input optical field transmission evolution of the corresponding structure. Compared to the traditional symmetrical multimode interference coupling structure, a significant redistribution of the optical field is induced by changing the refractive index of the phase transition material in the upper left corner of the multimode interference region. At this point, the output waveguide is still located at the first double image of the multimode interference region, and the optical power output from the lower output waveguide is significantly greater than that from the upper output waveguide. Based on this phenomenon, this embodiment utilizes laser phase transition technology to flexibly change the length of the phase transition region, thereby achieving a wide-range adjustable optical power distribution ratio at the two output ports of the device.

[0024] Further discussion of the specific method for achieving a wide range of adjustable power ratio in the embodiments of the present invention: the multimode region 102-a is an amorphous phase change material. An external laser is used to perform a laser phase change operation on the crystalline phase change material in the multimode region 102, causing part of the phase change material to transform from a crystalline to an amorphous state. This increases the size of the asymmetric structure of 102-a, thereby achieving the effect of gradually changing the power ratio at the two ports from 50:50 to 10:90. The relationship between the power ratio at the upper and lower output ports and the length of Lr is as follows: Figure 6 As shown. Furthermore, laser phase-change technology can also transform phase-change materials from an amorphous state to a crystalline state, corresponding to the reconfigurable nature of the device's function. Simultaneously, the phase-change material exhibits good phase-change cycle characteristics, meaning the device can be used repeatedly, and its output power ratio can be switched repeatedly. Compared to traditional optical power dividers (with a fixed power ratio for a single device), the device of this invention has a significant advantage in adjusting the optical power ratio.

[0025] In this embodiment of the invention, the length of the asymmetric structure can be changed at any time as needed and can be reused. Compared with the optical power dividers currently used, the device of the present invention has the advantages of adjustable optical power division ratio, non-volatile function, repeated use, and low processing cost.

[0026] In summary, the present invention has at least the following beneficial effects: In the optical power divider provided by this invention, based on a low-loss phase-change waveguide, an asymmetric structure is introduced in the multimode interference region, and laser phase-change technology is used to achieve flexible adjustment of the device's output optical power distribution ratio. Furthermore, the device in this embodiment has a large output optical power adjustment range, a simple structure, and low additional loss due to laser phase-change processing, thus possessing high application potential.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An optical power divider with a wide range of adjustable power ratio based on optical phase change materials, characterized in that: The structure consists of a substrate layer, an oxide layer, a silicon core layer, and a phase change material layer, from bottom to top. The device structure written in the phase change material layer includes an input waveguide, a multimode interference region, and an output waveguide. The multimode interference region includes an asymmetric structure and a subwavelength grating structure. The input waveguide is connected to the multimode interference region through a tapered structure. A subwavelength grating structure is added at the end of the multimode interference region and connected to the output waveguide through the tapered structure.

2. The optical power divider with a wide range of adjustable power ratio based on optical phase change materials according to claim 1, characterized in that: The asymmetric structure is trapezoidal, and the phase change material within the asymmetric structure changes from a crystalline state to an amorphous state.

3. The optical power divider with a wide range of adjustable power ratio based on optical phase change materials according to claim 1, characterized in that: The phase change material layer is deposited on the upper surface of the silicon core layer.

4. The optical power divider with a wide range of adjustable power ratio based on optical phase change materials according to claim 1, characterized in that: The output waveguides at both ends are connected to the multimode interference region through a tapered structure.

5. The optical power divider with a wide range of adjustable power ratio based on optical phase change materials according to claim 1, characterized in that: The substrate layer has a height of 500 μm, the oxide layer has a height of 2 μm, the silicon core layer has a height of 0.22 μm, and the phase change material layer has a height of 0.05 μm; the input waveguide and the output waveguide have a width of 1.2 μm and a length of 5 μm.

6. The optical power divider with a wide range of adjustable power ratio based on optical phase change materials according to claim 1, characterized in that: The width of the multimode interference region is 5 μm and the length is 28 μm.

7. The optical power divider with a wide range of adjustable power ratio based on optical phase change materials according to claim 1, characterized in that: The arbitrary power ratio of the optical power divider can be achieved by changing the size of the asymmetric structure in the multimode interference region. The length of the asymmetric structure can be adjusted from 0 to 25 μm.

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