A multifunctional analog computing device based on phase change materials

Abstract

The application discloses a multifunctional analog computing device based on a phase change material, and belongs to the technical field of photonic computing. The device is a transmission type multilayer film structure, and comprises, from top to bottom, a first distributed Bragg reflector, a phase change material layer and a second distributed Bragg reflector. The first distributed Bragg reflector and the second distributed Bragg reflector are both composed of high-refractive-index dielectric material films and low-refractive-index dielectric material films arranged alternately. The phase change material layer can reversibly change between amorphous state and crystalline state under external excitation, and has different refractive indexes in different crystalline states. When the phase change material is in different crystalline states, the angle-dependent transmission coefficient of the device for incident light changes, and low-pass filtering transfer function or high-pass filtering transfer function is realized respectively. The low-pass filtering and high-pass filtering functions of the device can be dynamically switched without changing the external light source condition by regulating the state of the phase change material, and different image processing tasks can be completed.

Description

Technical Field

[0001] This invention belongs to the field of photonic computing technology, specifically relating to a multifunctional analog computing device based on phase change materials. Background Technology

[0002] High-speed image processing has significant application value in visual computing and scientific research. With the rapid development of artificial neural networks, machine learning-based electronic vision computing has demonstrated outstanding performance in dynamic visual tasks such as target tracking, detection, and recognition. However, the integration density of silicon-based transistors is gradually approaching its physical limits, leading to a slowdown in the growth of computing power of electronic computing platforms, making it difficult to meet the demands of real-time, high-speed image processing in fields such as autonomous driving, intelligent robotics, and ultrafast dynamic imaging.

[0003] Photonic computing, with its advantages of low loss, high parallelism, ultra-high speed, and all-optical signal transmission, is considered an important technological path to overcome the bottlenecks of electronic computing. In recent years, nonlocal planar optical devices based on nanophotonic structures (such as thin film structures, metasurfaces, and photonic crystals) have been able to achieve all-optical image processing through spatial filtering, avoiding the problems of large size and low integration of traditional 4f optical systems. However, most existing nonlocal planar optical devices have limited functionality, typically only capable of edge extraction; while a few devices can achieve different functions by switching the incident light wavelength, they are significantly limited in biological imaging scenarios (such as fluorescence imaging) that depend on specific excitation wavelengths.

[0004] Therefore, how to develop an integrated non-local planar optical device that can dynamically switch between multiple image processing functions without changing the light source state has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a multifunctional analog computing device based on phase change materials. The device aims to dynamically switch between low-pass filtering (denoising) and high-pass filtering (edge ​​extraction) functions by adjusting the state of the phase change material without changing the external light source conditions, thereby completing different image processing tasks.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a multifunctional analog computing device based on phase change materials. The device is a transmissive multilayer film structure, comprising, from top to bottom: a first distributed Bragg mirror, a phase change material layer, and a second distributed Bragg mirror. Both the first and second distributed Bragg mirrors are composed of alternating high-refractive-index dielectric thin films and low-refractive-index dielectric thin films. The phase change material layer is capable of undergoing a reversible transition between an amorphous and crystalline state under external excitation, and has different refractive indices in different crystalline states. When the phase change material is in different crystalline states, the angle of incident light of the device changes depending on the transmission coefficient, thereby realizing a low-pass filter transfer function or a high-pass filter transfer function, respectively.

[0008] Furthermore, the combination of the high-refractive-index dielectric material and the low-refractive-index dielectric material is selected from any of the following: Ta2O5 and SiO2, Si3N4 and SiO2, TiO2 and SiO2, Nb2O5 and SiO2.

[0009] Furthermore, the phase change material layer is Sb2Se3, GeSe, or Se.

[0010] Furthermore, the thickness of the phase change material layer is 252 nm to 272 nm.

[0011] Furthermore, both the first and second distributed Bragg reflectors include 3-7 film layer pairs, in which the thickness of the high refractive index material layer is 257 nm to 277 nm and the thickness of the low refractive index material layer is 175 nm to 195 nm.

[0012] Furthermore, the device also includes a substrate, which is a 500 μm thick fused silica substrate, on which the second distributed Bragg mirror is formed.

[0013] Furthermore, the high-pass filter transfer function The edge extraction function is implemented as follows:

[0014] (1)

[0015] The low-pass filter transfer function The expression for achieving noise reduction is as follows:

[0016] (2)

[0017] in, The wave vector represents any direction, and n is a positive integer representing the order.

[0018] Furthermore, a reversible switching between amorphous and crystalline states is achieved through thermal annealing. Specifically, the device is placed in a tube furnace and annealed at 300°C for 30 minutes under an argon atmosphere, causing the phase change material layer to transform from an amorphous state to a crystalline state. By controlling the cooling rate or subsequent heat treatment, a reversible transition from crystalline to amorphous state is achieved.

[0019] Secondly, this invention proposes a method for fabricating a multifunctional analog computing device based on phase change materials, comprising the following steps:

[0020] Step 1: On a fused silica substrate, a second distributed Bragg mirror is formed by alternately depositing Ta2O5 and SiO2 layers by magnetron sputtering.

[0021] Step 2: On the second distributed Bragg mirror, a Sb2Se3 layer is deposited by magnetron sputtering as a phase change material layer;

[0022] Step 3: On the phase change material layer, high refractive index material layer and low refractive index material layer are deposited alternately using the same process parameters as in Step 1 to form the first distributed Bragg reflector;

[0023] Step 4: Achieve a reversible phase transition of the Sb2Se3 layer between the amorphous and crystalline states through controlled thermal annealing.

[0024] Thirdly, the present invention provides an optical imaging system, including a light source, an imaging object, an imaging lens, and the aforementioned multifunctional analog computing device; light emitted from the light source is collimated and then illuminates the target to be measured; transmitted or reflected light is imaged by the objective lens and then acts on the device of the present invention; spatial frequency modulation is performed inside the device, and then the imaging system records and outputs the image. In crystalline mode, the output image exhibits a significant edge enhancement effect; in amorphous mode, noise in the output image is effectively suppressed while structural information is preserved.

[0025] Compared with the prior art, the advantages of the present invention are as follows:

[0026] 1. This invention realizes two optical transfer functions, low-pass filtering and high-pass filtering, integrates two functions, image denoising and edge extraction, and expands the application scenarios of a single device;

[0027] 2. This invention does not require changing the light field conditions of the external light source; it achieves dynamic switching of functions simply by controlling the temperature to change the state of the phase change material.

[0028] 3. The present invention has a compact structure, does not require a complex 4f optical system, is easy to integrate, and can realize a miniaturized and integrated optical simulation computing system. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0030] Figure 1 This is a schematic diagram illustrating the function switching of the multifunctional analog computing device based on phase change materials according to the present invention;

[0031] Figure 2 This is a schematic diagram of the structure of the multifunctional simulation computing device based on phase change materials of the present invention;

[0032] Among them, 2-1 consists of seven film layers with a thickness of 267 nm for Ta2O5 and 185 nm for SiO2; 2-2 consists of a 262 nm thick phase change material Sb2Se; and 2-3 consists of a 500 μm thick quartz substrate.

[0033] Figure 3 The graphs show the optical transfer function curves of the analog computing device of the present invention under two states.

[0034] Where a represents the crystalline state and b represents the amorphous state;

[0035] Figure 4 This is an example optical path diagram of the device of the present invention applied to an optical imaging system;

[0036] Figure 5 The experimental results of the device of the present invention in amorphous state (noise reduction) and crystalline state (edge ​​extraction) are shown.

[0037] Figure 6 The results show the repeatability test results of the transfer functions of crystalline and amorphous states under multiple switching experiments;

[0038] Figure 7 The results of the transfer function stability test under different film thickness deviations;

[0039] Figure 8 The figure shows the comparative transfer function curve after replacing Sb2Se3 with GeTe.

[0040] Figure 9 The figure shows the comparative transfer function curve after replacing Sb2Se3 with GeSe. Detailed Implementation

[0041] To clearly and completely describe the technical solution and its specific working process of the present invention, the specific embodiments of the present invention are as follows, in conjunction with the accompanying drawings:

[0042] Example 1

[0043] like Figure 2 As shown, this embodiment provides a multifunctional simulation computing device based on phase change materials. It employs a transmission-type symmetrical multilayer film structure built on a 500 μm thick fused silica substrate. From top to bottom, the device includes: a first distributed Bragg mirror, a phase change material layer, and a second distributed Bragg mirror. Both the first and second distributed Bragg mirrors comprise seven film layer pairs, each consisting of a 267 nm thick Ta₂O₅ layer and a 185 nm thick SiO₂ layer. The phase change material layer is Sb₂Se₃ with a thickness of 262 nm. The phase change material layer can undergo a reversible transition between an amorphous and crystalline state under external excitation, and exhibits different refractive indices in different crystalline states. When the phase change material is in different crystalline states, the device changes its transmission coefficient depending on the angle of incident light, thereby realizing either a low-pass filter transfer function or a high-pass filter transfer function.

[0044] This multifunctional analog computing device has two simulation functions: one is noise reduction using a low-pass filter transfer function, and the other is edge extraction using a high-pass filter transfer function. To achieve these two functions, the device employs a multilayer film structure based on the phase change material Sb₂Se₃. Since the refractive index of Sb₂Se₃ changes with temperature, its optical transfer function can be altered through its own properties without changing the external light source conditions.

[0045] According to the Green's function principle in Fourier optics, to realize the high / low-pass optical transfer function (expressions are (1) and (2) respectively), where (where n is a positive integer representing the order) represents a wave vector in any direction, and multilayer film devices are needed to generate angle-dependent transmission / reflection coefficients.

[0046] (1)

[0047] (2)

[0048] like Figure 1 As shown, this multilayer film structure forms an optical response mechanism similar to a Fabry-Perot resonator. When light is incident on this structure, different incident angles correspond to different transverse wave vector components. The propagation of each spatial frequency component within the multilayer film is subject to angle-dependent transmission modulation, thus forming a nonlocal optical response. By rationally designing the thickness of each layer and the refractive index of the material, the device exhibits different angular transmission characteristics under different phase transition states, thereby constructing the corresponding optical transfer function.

[0049] In practical implementation, when Sb₂Se₃ is in the crystalline state, its high refractive index alters the cavity resonance conditions, enhancing the transmission of large-angle (high spatial frequency) light components while suppressing small-angle (low spatial frequency) components. This results in a high-pass filter-type optical transfer function, enabling image edge extraction. When Sb₂Se₃ is in the amorphous state, its lower refractive index preferentially transmits small-angle light components while suppressing high-angle components, forming a low-pass filter-type optical transfer function, enabling image noise reduction. The optical transfer functions of the device in both Sb₂Se₃ states are as follows: Figure 3 As shown in the figure, the crystalline state exhibits a high-pass filter transfer function ( As its transfer function increases, the amorphous state exhibits a low-pass filter transfer function. The decrease in the transfer function value as its value increases indicates that this device can implement two transfer functions. The high-pass transfer function is for edge extraction, and the low-pass transfer function is for noise reduction. Since image edges are high-frequency information, they can be extracted using the high-pass transfer function, i.e., edge extraction. Small-sized noise in the image is also high-frequency information, and it can be suppressed using the low-pass transfer function, i.e., noise reduction.

[0050] The switching between the two operating states is achieved through a thermally induced phase transition. In this embodiment, the fabricated device is placed in a tube furnace and heated to 300°C under an argon protective atmosphere and held for 30 minutes, which transforms Sb₂Se₃ from an amorphous state to a crystalline state. Through appropriate heat treatment or rapid cooling, the reverse transition from crystalline to amorphous state can be achieved, thus realizing reversible switching of the device's function. This invention does not rely on changes in the wavelength, polarization, or optical path structure of the incident light; different optical computing functions can be achieved solely through material state manipulation.

[0051] Three sets of experiments involving switching between crystalline and amorphous states were repeatedly recorded. Figure 6 As shown, the crystal exhibits a high-pass filter transfer function ( This represents the normalized transverse wave vector. As the value of the transfer function increases, so does the value of the transfer function. Represents the wave number in a vacuum. =2π / λ, where λ is the wavelength of the incident light), and the amorphous state exhibits a low-pass filter transfer function ( As the value of the transfer function decreases (as it increases), the overall trend of the transfer function remains the same, with no performance degradation.

[0052] Example 2

[0053] In this embodiment, Si3N4 (214nm) / SiO2 (156nm), TiO2 (257nm) / SiO2 (189nm), or Nb2O5 (231nm) / SiO2 (164nm) are used instead of Ta2O5 (267nm) / SiO2 (185nm) as the film layer pair materials for the distributed Bragg reflector. Other structural parameters (film thickness, number of periods, phase change material thickness, etc.) are adjusted equivalently based on the refractive index differences. Experimental results show that the above material combinations can achieve reversible switching between high-pass and low-pass filter transfer functions when the phase change material is in different states, proving the universality of the material selection for the distributed Bragg reflector in this invention.

[0054] Example 3

[0055] This embodiment sets up two groups of devices with randomly varying film thicknesses of 5 nm and 10 nm, respectively. Experimental results show that the transfer function of the devices in both cases follows the same trend as the parameter group in Example 1. Figure 7 As can be seen, its transfer function in the crystalline state is always related to... The high-pass transfer function increases with increasing numerical value. Conversely, in the amorphous state, the transfer function increases with increasing numerical value. The value that decreases with increasing values ​​is the low-pass transfer function. Therefore, within the range of film thickness variation given in this invention, devices composed of multilayer films can achieve edge extraction and noise reduction effects in both phase transition states.

[0056] Example 4

[0057] In this embodiment, the phase change material layer is replaced with GeSe, with a thickness of 258 nm. All other structural parameters are the same as in Embodiment 1. Experimental results are as follows: Figure 9 As shown. From Figure 9 As can be seen from this, its transfer function in the crystalline state changes with... The value increases with increasing amplitude, exhibiting a high-pass transfer function; in the amorphous state, it increases with increasing amplitude. The value increases and then decreases, exhibiting a low-pass transfer function. Therefore, it has the effect of extracting high-frequency information from image edges and suppressing high-frequency information of noise.

[0058] Comparative Example 1

[0059] The comparative example uses GeTe phase change material instead of Sb2Se3, with other structural parameters the same as in Example 1. The experimental results are as follows. Figure 8 As shown. From Figure 8 As can be seen from this, its transfer function changes with the state of crystal and amorphous states. The numerical value remains basically unchanged as it increases, and it does not exhibit a low-pass or high-pass transfer function. Therefore, it does not have the effect of extracting high-frequency information from image edges or suppressing high-frequency information of noise.

[0060] Example 5

[0061] This embodiment proposes a method for fabricating a multifunctional analog computing device based on phase change materials, including the following steps:

[0062] (1) The 500μm thick fused silica substrate was ultrasonically cleaned in acetone, isopropanol and deionized water in sequence, and then treated with oxygen plasma to remove organic residues.

[0063] (2) On a fused silica substrate, radio frequency magnetron sputtering was used to alternately deposit Ta2O5 (267nm) and SiO2 (185nm) in an argon atmosphere (pressure 0.5Pa, flow rate 50sccm) for a total of 7 cycles with a target-substrate distance of 55mm to form a second distributed Bragg reflector.

[0064] (3) Using stoichiometric Sb2Se3 target material, a 262nm thick Sb2Se3 layer was deposited by magnetron sputtering at 80W RF power to obtain a smooth and uniform amorphous thin film.

[0065] (4) The first distributed Bragg mirror is deposited using the same process parameters as the second distributed Bragg mirror to form a symmetrical multilayer structure.

[0066] Example 6

[0067] like Figure 4 As shown, this embodiment provides an optical imaging system, including a light source, an imaging object, an imaging lens, and the aforementioned multifunctional analog computing device. Light emitted from the light source is collimated and then illuminates the target. Transmitted or reflected light is imaged by the objective lens and then acts on the device of this invention. Spatial frequency modulation is performed within the device, and the imaging system then records and outputs the image. In crystalline mode, the output image exhibits a significant edge enhancement effect; in amorphous mode, noise in the output image is effectively suppressed while structural information is preserved.

[0068] like Figure 5 As shown, the device of this invention can be applied to biological sample imaging. For unstained cell or tissue samples, in crystalline mode, it can enhance cell boundaries and tissue structure contours, improving structural recognition; in amorphous mode, it can reduce speckle noise and background interference, making the image smoother and clearer. This device can also be used as an optical preprocessing unit, combined with subsequent image recognition algorithms, to improve recognition efficiency and accuracy.

[0069] The above description is merely a preferred embodiment of the present invention and does not limit the scope of the patent. Any modifications, equivalent substitutions, or improvements made to parameters such as material type, number of layers, and thickness within the concept and principles of the present invention should be included within the protection scope of the present invention.

[0070] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0071] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0072] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A multi-functional analog computing device based on phase change materials, characterized in that, The device is a transmissive multilayer film structure, comprising, from top to bottom: a first distributed Bragg mirror, a phase change material layer, and a second distributed Bragg mirror; both the first and second distributed Bragg mirrors are composed of alternating high-refractive-index dielectric thin films and low-refractive-index dielectric thin films; the phase change material layer undergoes a reversible transition between an amorphous and crystalline state under external excitation, and has different refractive indices in different crystalline states; when the phase change material is in different crystalline states, the angle of incident light of the device changes depending on the transmission coefficient, thereby realizing a low-pass filter transfer function or a high-pass filter transfer function respectively.

2. A multi-functional analog computing device based on phase change material as claimed in claim 1 wherein, The combination of the high-refractive-index dielectric material and the low-refractive-index dielectric material is selected from any of the following: Ta2O5 and SiO2, Si3N4 and SiO2, TiO2 and SiO2, Nb2O5 and SiO2.

3. A multi-functional analog computing device based on phase change material as claimed in claim 1 wherein, The phase change material layer is Sb2Se3, GeSe, or Se.

4. The multifunctional analog computing device based on phase change materials as described in claim 1, characterized in that, The thickness of the phase change material layer is 252 nm to 272 nm.

5. A multifunctional simulation computing device based on phase change materials as described in claim 1, characterized in that, Both the first and second distributed Bragg reflectors include 3-7 film layer pairs, with the thickness of the high refractive index material layer in each film layer pair being 257nm to 277nm and the thickness of the low refractive index material layer being 175nm to 195nm.

6. The multifunctional analog computing device based on phase change materials as described in claim 1, characterized in that, The device also includes a substrate, which is a 500 μm thick fused silica substrate, on which the second distributed Bragg mirror is formed.

7. A multifunctional simulation computing device based on phase change materials as described in claim 1, characterized in that, The high-pass filter transfer function implements the edge extraction function, and its expression is as follows: （1） The low-pass filter transfer function performs noise reduction, and its expression is as follows: （2） in, The wave vector represents any direction, and n is a positive integer representing the order.

8. The multifunctional analog computing device based on phase change materials as described in claim 1, characterized in that, The reversible switching between amorphous and crystalline states is achieved through thermal annealing. Specifically, the device is placed in a tube furnace and annealed at 300°C for 30 minutes under an argon atmosphere, causing the phase change material layer to change from amorphous to crystalline. The reversible transition from crystalline to amorphous state is achieved by controlling the cooling rate or subsequent heat treatment.

9. The method for fabricating a multifunctional analog computing device based on phase change materials as described in claim 1, characterized in that, Includes the following steps: Step 1: On a fused silica substrate, a second distributed Bragg mirror is formed by alternately depositing Ta2O5 and SiO2 layers by magnetron sputtering. Step 2: On the second distributed Bragg mirror, a Sb2Se3 layer is deposited by magnetron sputtering as a phase change material layer; Step 3: On the phase change material layer, high refractive index material layer and low refractive index material layer are deposited alternately using the same process parameters as in Step 1 to form the first distributed Bragg reflector; Step 4: Achieve a reversible phase transition of the Sb2Se3 layer between the amorphous and crystalline states through controlled thermal annealing.

10. An optical imaging system, characterized in that, The invention includes a light source, an imaging object, an imaging lens, and a multifunctional analog computing device as described in any one of claims 1-8. The light emitted by the light source is collimated and then illuminates the target to be measured. The transmitted or reflected light is imaged by the objective lens and then acts on the device of the invention. After spatial frequency modulation is completed inside the device, the imaging system records and outputs the image. In crystalline mode, the output image exhibits a significant edge enhancement effect. In amorphous mode, the noise of the output image is effectively suppressed and the structural information is preserved.

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