All-optical waveguide device and array for phase change polymorphic storage and calculation

Abstract

The invention discloses a phase change polymorphic storage and calculation all-optical waveguide device and array, which comprises a bottom substrate layer and a top optical waveguide layer, the optical waveguide layer comprises a covering protection layer, a phase change material layer, a waveguide dielectric layer and a shallow etching layer, and the covering protection layer and the phase change material layer are integrated above the center of the waveguide dielectric layer. According to the invention, by utilizing the characteristic that the amorphous phase and the crystal phase of the phase-change material indium antimony tellurium have obvious transmissivity difference in an optical communication wave band, the transmissivity of the device is driven to gradually change through a controllable adjustment mode of gradually non-crystallizing an interface, so that multi-logic-state storage of a single device is realized; and the matrix calculation of the silicon-based all-optical waveguide is realized by constructing a silicon optical waveguide device array.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-based photon storage, and particularly relates to an all-optical waveguide device and array for phase change multi-state storage and computing. Background Art

[0002] Silicon-based photonic devices have a wide range of applications. Especially in the next-generation computing architecture, silicon photonics technology can significantly improve the data transmission rate between processors, memories, and storage units, and solve the bandwidth bottleneck problem in traditional electronic architectures. All-optical neural networks utilize the characteristics of light to perform key matrix operations in neural networks, which can greatly accelerate artificial intelligence (AI) workloads and significantly reduce power consumption at the same time.

[0003] Integrating phase change memory cells on a silicon photon platform, such as germanium antimony telluride Ge 2 Sb 2 Te 5 (GST), based on the large transmittance change between its crystalline phase and amorphous phase, can achieve all-optical multi-state storage and neuromorphic matrix operations. However, on the one hand, both the crystalline phase and amorphous phase of germanium antimony telluride are semiconducting, and its switching ratio is small. Therefore, it is difficult to improve its multi-state storage density, and it is difficult to further increase the scale of matrix calculations based on multiple logic states. On the other hand, the phase change process of germanium antimony telluride is random, resulting in poor consistency in the programming process of multiple logic states. Therefore, the accuracy in matrix calculations based on multiple logic states cannot be further improved, restricting its application. Summary of the Invention

[0004] In order to overcome the above defects existing in the prior art, the present invention provides an all-optical waveguide device and array for phase change multi-state storage and computing. By utilizing the significant transmittance difference between the amorphous phase and crystalline phase of the phase change material indium antimony telluride in the optical communication band, and through a controllable adjustment method of stepwise amorphization at the interface, the transmittance of the device is gradually changed, thereby realizing multi-logic state storage of a single device, and realizing its silicon-based all-optical waveguide matrix calculation by constructing a silicon optical waveguide device array.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] An all-optical waveguide device for phase change multi-state storage and computing, comprising a substrate layer and an optical waveguide layer. The optical waveguide layer includes a covering protection layer, a phase change material layer, a waveguide dielectric layer, and a shallow etching layer. The covering protection layer and the phase change material layer are integrated above the center of the waveguide dielectric layer, and the shallow etching layer is located on the substrate layer;

[0007] The phase change material of the phase change material layer is In x Sb y Te z, where 45 ≤ x ≤ 55, 15 ≤ y ≤ 20, 30 ≤ z ≤ 35, and x + y + z = 100; the phase change material In x Sb y Te z The amorphous phase has semiconductor characteristics, and the crystalline phase has metallic characteristics. Based on the phase change material In x Sb y Te z The all-optical waveguide device has a switching ratio of more than 2.5 dB;

[0008] The In x Sb y Te z By taking the whole as the crystalline phase as the initial state and adjusting the volume ratio of the crystalline phase and the amorphous phase in the device by gradually amorphizing from the interface, the transmittance of the device changes continuously and quantitatively controllably, so as to realize quantitatively controllable multi-state storage in a single device.

[0009] The method for the phase change material layer to undergo interface gradual amorphization phase change is to load a laser pulse signal, and the degree of amorphization of the phase change material is regulated by adjusting the power and pulse width of the laser pulse. Different degrees of amorphization (volume ratio of the crystalline phase and the amorphous phase) correspond to different transmittances of the device, and each transmittance corresponds to an identifiable logic state; the change amplitude of the volume of the amorphous phase in the device can be regulated by adjusting the change step of the power and pulse width, and further the transmittance difference between adjacent logic states can be regulated.

[0010] Furthermore, the power range of the laser pulse signal is from 20 mW to 200 mW, and the pulse width range is from 100 fs to 100 ms; the pulses required for gradual amorphization should set the power and pulse width to increase gradually from small to large according to the device situation, and the step size is adjusted according to the number of identifiable logic states required. The smaller the step size, the smaller the change in transmittance, and the more the number of identifiable logic states in a single device.

[0011] When the phase change material is in a completely amorphous phase, it corresponds to the open state of the device. When the phase change material is in a completely crystalline phase, it corresponds to the closed state of the device. When the phase change material is in a completely amorphous phase, a high-power laser pulse signal or high-temperature annealing operation can be loaded to make the phase change material undergo complete crystallization and switch to the closed state.

[0012] The bottom substrate layer is silicon dioxide, with a thickness ≥ 50 nm; the shallow etching layer 4 is silicon, with a thickness of 100 nm ≤ thickness ≤ 200 nm; the waveguide dielectric layer is a silicon waveguide or a silicon nitride waveguide, with a thickness of 200 nm ≤ thickness ≤ 350 nm; the covering protective layer is indium tin oxide, with a thickness ≥ 5 nm.

[0013] The all-optical waveguide device for phase change multi-state storage and calculation can use any one of a ridge optical waveguide device, a planar optical waveguide device, and a strip optical waveguide device.

[0014] When the all-optical waveguide device for phase-change multi-state storage and computing is a ridge optical waveguide device, the waveguide dielectric layer in the middle and on both sides of the shallow etching layer has a convex structure, and a phase-change material layer and a covering protective layer are arranged on the middle waveguide dielectric layer. An all-optical waveguide device array for phase-change multi-state storage and computing is used for optical signal processing and matrix-vector multiplication operation;

[0015] The all-optical waveguide device array is composed of m×n all-optical waveguide devices. The devices form an adjustable optical waveguide matrix of m columns multiplied by n rows. The logic state of each device serves as a weight in the matrix. Each device can be logically reconfigured through the above-mentioned multi-logic-state controllable and reversible regulation. After reconfiguration, each device can be individually written with a new weight, and a new matrix can be constructed in a local or overall area for new calculation and solution.

[0016] By adjusting the volume ratio of the crystal phase and the amorphous phase in the device in a step-by-step phase change manner starting from the self-interface, the transmittance of the device changes continuously in a quantitatively controllable manner, and stable recognition of more than 4-bit continuous logic states is achieved in a single device.

[0017] Advantages of the present invention:

[0018] The present invention proposes an all-optical waveguide device for phase-change multi-state storage and computing. The amorphous phase of the phase-change material indium antimony telluride has semiconductor characteristics, and the crystal phase has metal characteristics. The phase change between the two is a "semiconductor-metal" transition, which has a larger recognition window than the "semiconductor-semiconductor" transition of traditional phase-change materials. Therefore, the device has a larger switching ratio.

[0019] The present invention proposes an all-optical waveguide device for phase-change multi-state storage and computing. By setting the parameters of the laser pulse, the phase-change material indium antimony telluride can be gradually amorphized along the interface, so as to quantitatively and controllably adjust the volume ratio of the amorphous phase and the crystal phase of the phase-change material layer; under this condition, the transmittance of the device changes continuously and controllably, so as to achieve controllable multi-logic-state recognition in a single device.

[0020] The present invention proposes an all-optical waveguide device array for phase-change multi-state storage and computing. Each device has a large switching ratio and continuously quantitatively adjustable logic states. Therefore, it can either construct a dedicated array of a specific matrix or adjust a variable matrix according to actual needs; each device can be repeatedly erased and written, and has strong adjustability and information processing capabilities. By inputting an optical signal into the array and setting the input optical signal according to the optical loss situation of each device, the output optical signal after passing through the matrix is the operation result. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a ridge all-optical waveguide phase-change storage device.

[0022] Figure 2 It is a schematic diagram of multiple logic states of an all-optical waveguide phase change memory device.

[0023] Figure 3 It is a schematic diagram of an all-optical waveguide phase change memory device array. Specific implementation manners

[0024] The present invention will be further described in detail below with reference to the accompanying drawings.

[0025] Figure 1 It is a schematic structural diagram of a ridge-shaped all-optical waveguide phase change memory device. The structural unit of the shown device includes a covering protection layer 1, a phase change material layer 2, a waveguide dielectric layer 3, a shallow etching layer 4, and a bottom substrate layer 5. The phase change material layer 2 and the covering protection layer 1 are integrated above the center of the waveguide dielectric layer 3.

[0026] Figure 2 It is a schematic diagram of multiple logic states of an all-optical waveguide phase change memory device. The pulse width of the pulse is preset by precisely regulating the pulse power through a variable optical attenuator to control the gradual amorphization of the phase change material, and further control the volume ratio of the amorphous phase region and the crystal phase region in the device, so that the transmittance changes gradually and continuously. This figure shows the logic states of 20-bit (>4 bits) continuous and stable recognition.

[0027] Figure 3 It is a schematic diagram of an all-optical waveguide phase change memory device array. The array is an m×n array composed of optical waveguide phase change memories, and each row-column intersection is an all-optical waveguide phase change memory device. The logic state stored in each all-optical waveguide phase change memory device serves as the weight of the matrix, thus constructing a complete matrix. According to the optical loss situation of each device in the matrix, the input optical signal X is set, and the optical signal Y after passing through the matrix is read to complete the matrix operation.

[0028] The present invention will be further illustrated below with specific embodiments as examples.

[0029] Embodiment

[0030] The structure of the optical waveguide phase change memory described herein is as Figure 1 shown. In some regions of the silicon dioxide protection layer on the top of the silicon optical waveguide sample, air grooves are formed above the silicon waveguide through etching for the hetero-integration of indium antimonide telluride thin film deposition and the silicon waveguide. The thickness of the silicon waveguide is 220 nm, the shallow etching depth is 150 nm, and the waveguide width is 450 nm. Next, AZ5214E photoresist is spin-coated on the sample, and through photolithography exposure and development, the window for depositing the phase change material is opened. The indium antimonide telluride thin film and the indium tin oxide protection layer are deposited by magnetron sputtering, and finally the photoresist is removed to realize the hetero-integration of the indium antimonide telluride phase change thin film and the silicon-on-insulator optical waveguide, thereby obtaining an indium antimonide telluride optical waveguide phase change memory.

[0031] Reversible switching operation of the all-optical waveguide phase-change memory device can be achieved by adjusting the waveform and power of the loaded laser pulse. In the as-deposited device, the indium antimonide telluride thin film is amorphous. Annealing treatment is first carried out to obtain the crystal phase, and the device is in the off state at this time. The extinction ratio of the device is defined as ER = 10log 10 (T 0 / T C ), where ER is the extinction ratio (Extinction Ratio), T 0 is the transmission value measured in real time, and T C is the transmission value after the device is annealed (i.e., the thin film is entirely in the crystal phase). By using the all-optical pump-probe experimental platform to adjust the waveform and power of the loaded laser pulse, an extinction ratio of ~2.52 dB is obtained for the all-optical waveguide phase-change memory.

[0032] For multi-logic state programming of the all-optical waveguide phase-change memory, by precisely regulating the pulse power with a variable optical attenuator and presetting the pulse width of the laser pulse, the volume ratio of the crystal phase and amorphous phase regions of the phase-change material layer can be effectively regulated, enabling a gradual and continuous change in the transmittance, that is, multiple intermediate logic values are configured between the fully off "0" state and the fully on "1" state. Stable identification of more than 4 bits of logic values is achieved through dynamic control of the number and amplitude normalization transmission display of the pulses. At the same time, five repeated experiments are carried out, demonstrating good repeatability and consistency during the fine-tuning process.

[0033] Taking the refractive index of each all-optical waveguide phase-change memory device as the weight value of the matrix, a certain amount of light is absorbed according to its specific phase configuration. When the phase-change layer is in the crystal phase, most of the incident light is absorbed, representing the "0" state; while when the phase-change layer is in the amorphous phase, most of the light is transmitted, thus representing "1". By controllably switching the ratio of the amorphous state and the crystalline state in the all-optical waveguide phase-change memory cell, intermediate transmission states can be selected. In the entire m×n matrix vector multiplication operation, the input vector is an optical signal encoded and sent to different matrices for input, and parallel operations are achieved under an optical signal of a given wavelength, and the output optical signal is the operation result.

Claims

1. An all-optical waveguide device for phase change polymorphic storage and computing, characterized in that: The optical waveguide layer comprises a substrate layer (5) and an optical waveguide layer, wherein the optical waveguide layer comprises a cover protection layer (1), a phase change material layer (2), a waveguide medium layer (3) and a shallow etching layer (4) which are arranged in sequence, wherein the cover protection layer (1) and the phase change material layer (2) are integrated above the center of the waveguide medium layer (3), and the shallow etching layer (4) is located on the substrate layer (5); The phase change material of the phase change material layer (2) is In x Sb y Te z , wherein 45≤x≤55, 15≤y≤20, 30≤z≤35, and x+y+z=100; the phase change material In x Sb y Te z The amorphous phase has semiconductor characteristics, the crystalline phase has metallic characteristics, and the phase change material In x Sb y Te z The all-optical waveguide device has a switching ratio of more than 2.5dB.

2. The all-optical waveguide device for phase change polymorphic storage and computing according to claim 1, characterized in that: In x Sb y Te z By taking the overall crystalline phase as the initial state and adjusting the volume ratio of the crystalline phase to the amorphous phase in the device by gradually amorphizing starting from the interface, the transmittance of the device undergoes a quantitatively controllable continuous and step-by-step change, thereby achieving quantitatively controllable multi-state storage in a single device.

3. The all-optical waveguide device for phase change polymorphic storage and computing according to claim 2, characterized in that: The method for causing the phase change material layer (2) to undergo a gradual amorphous phase change at the interface is to load a laser pulse signal; The degree of amorphization of the phase change material is controlled by adjusting the power and pulse width of the laser pulse. Different degrees of amorphization correspond to different transmittances of the device, and each transmittance corresponds to a recognizable logic state. The volume change amplitude of the amorphous phase in the device is controlled by adjusting the change step of the power and pulse width, thereby controlling the transmittance difference between adjacent logic states.

4. The all-optical waveguide device for phase change polymorphic storage and computing according to claim 3, characterized in that: The power range of the laser pulse signal is 20mW to 200mW, and the pulse width range is 100fs to 100ms. The pulse required for gradual amorphization should be set according to the device situation, with the power and pulse width gradually increasing from small to large. The step size is adjusted according to the required number of recognizable logic states. The smaller the step size, the smaller the transmittance change, and the more recognizable logic states in a single device.

5. The all-optical waveguide device for phase change polymorphic storage and computing according to claim 1, characterized in that: When the phase change material is in a completely amorphous phase, the device is in an open state, and when the phase change material is in a completely crystalline phase, the device is in a closed state. When the phase change material is in a completely amorphous phase, a high-power laser pulse signal or a high-temperature annealing operation can be loaded to make the phase change material completely crystallize and switch to a closed state.

6. The all-optical waveguide device for phase change polymorphic storage and computing according to claim 1, characterized in that: The bottom substrate layer (5) is silicon dioxide with a thickness of ≥50nm; the shallow etching layer (4) is silicon with a thickness of 100nm≤≤200nm; the waveguide medium layer (3) is a silicon waveguide or a silicon nitride waveguide with a thickness of 200nm≤≤350nm; and the covering protection layer (1) is indium tin oxide with a thickness of ≥5nm.

7. The all-optical waveguide device for phase change polymorphic storage and computing according to claim 1, characterized in that: The all-optical waveguide device for phase-change polymorphic storage and computing may use any one of a ridge optical waveguide device, a planar optical waveguide device and a strip optical waveguide device.

8. The all-optical waveguide device for phase change polymorphic storage and computing according to claim 7, characterized in that: When the all-optical waveguide device for phase-change polymorphic storage and calculation is a ridge-shaped optical waveguide device, the middle and both sides of the shallow etched layer (4) are waveguide medium layers (3) with convex structures, and a phase-change material layer (2) and a covering protection layer (1) are arranged on the middle waveguide medium layer (3).

9. An all-optical waveguide device array for phase change polymorphic storage and computing, characterized in that: The array is used to perform optical signal processing and matrix-vector multiplication operations; The all-optical waveguide device array is composed of m×n all-optical waveguide devices according to any one of claims 1 to 6, and the devices form an adjustable optical waveguide matrix of m columns and n rows. The logic state of each device serves as a weight in the matrix, and each device can be reconstructed in logic state through the above-mentioned controllable and reversible regulation of multiple logic states. After reconstruction, each device can be written with a new weight individually, and a new matrix can be constructed in a local or overall area to perform a new calculation solution.

10. The all-optical waveguide device array for phase change polymorphic storage and computing according to claim 9, characterized in that: By adjusting the volume ratio of the crystalline phase to the amorphous phase in the device through a gradual phase change starting from the interface, the transmittance of the device can undergo a quantitatively controllable continuous and step-by-step change, achieving stable recognition of more than 4-bit continuous logic states in a single device.

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