On-chip optical element, preparation method thereof and integrated optical element

Abstract

The invention provides an on-chip optical element, a preparation method thereof and an integrated optical element. The on-chip optical element comprises a substrate, an input coupling waveguide located on the substrate, an output coupling waveguide located on the substrate and a modulation structure. The modulation structure comprises a phase change material layer located on the substrate, the phase change material layer is a continuous film layer and comprises a plurality of units, and the refractive indexes of at least two units are different; and the input coupling waveguide and the output coupling waveguide are respectively positioned at the side parts of the modulation structure, so that light rays emitted to the modulation structure through the input coupling waveguide are propagated along a direction parallel to the surface of the phase change material layer. The integrated optical element includes the on-chip optical element.

Description

Technical Field

[0001] This application relates to the field of optical signal processing technology, and in particular to an on-chip optical element and its fabrication method, and an integrated optical element. Background Technology

[0002] With the rapid development of big data, cloud computing, and artificial intelligence, the complexity of artificial intelligence algorithm models has increased dramatically. The traditional architecture based on electronic chips as computing carriers can no longer meet the requirements of algorithm models for computing power and energy efficiency. Since the propagation of light in a medium has natural advantages such as high speed, high parallelism, high bandwidth, and low power consumption, computation based on the limited propagation of light in a medium has received high attention both at home and abroad in recent years.

[0003] Currently, once optical computing devices are manufactured, their performance is fixed and cannot be reconfigured, which limits their applications. Summary of the Invention

[0004] This application provides an on-chip optical element and its fabrication method, as well as an integrated optical element.

[0005] According to a first aspect of the embodiments of this application, an on-chip optical element is provided, the on-chip optical element comprising:

[0006] Substrate;

[0007] The input coupling waveguide is located on the substrate;

[0008] The output coupling waveguide is located on the substrate;

[0009] A modulation structure; the modulation structure includes a phase change material layer located on the substrate, the phase change material layer being a continuous film layer comprising multiple units, at least two of the units having different refractive indices; the input coupling waveguide and the output coupling waveguide are respectively located on the side of the modulation structure, such that light rays incident on the modulation structure through the input coupling waveguide propagate in a direction parallel to the surface of the phase change material layer.

[0010] In one embodiment, the states of the plurality of units include a crystalline state, an amorphous state, and an intermediate state between the crystalline state and the amorphous state, wherein the refractive index of the intermediate state unit is between the refractive index of the crystalline state unit and the refractive index of the amorphous state unit.

[0011] In one embodiment, the phase change material layer is in direct contact with the substrate; the thickness of the phase change material layer ranges from 200 nm to 400 nm.

[0012] In one embodiment, the modulation structure further includes a waveguide structure layer located between the substrate and the phase change material layer, the waveguide structure layer being in direct contact with the phase change material layer; the thickness of the phase change material layer is in the range of 10 nm to 50 nm.

[0013] In one embodiment, the plurality of units are arranged in multiple rows and columns.

[0014] In one embodiment, the material of the phase change material layer includes at least one of Ge2Sb2Te5 and Sb2Se3.

[0015] In one embodiment, the modulation structure further includes a protective layer located on the side of the phase change material layer away from the substrate.

[0016] According to a second aspect of the embodiments of this application, an integrated optical element is provided, the integrated optical element including the on-chip optical element described above.

[0017] According to a third aspect of the embodiments of this application, a method for fabricating an on-chip optical element is provided, the method comprising:

[0018] An intermediate structure is provided, the intermediate structure including a substrate, an input coupling waveguide, an output coupling waveguide and a modulation structure located on the substrate, the modulation structure including a phase change material layer, the input coupling waveguide and the output coupling waveguide being located on the side of the modulation structure respectively; the phase change material layer is a continuous film layer including multiple units, and the initial state of the phase change material layer is amorphous;

[0019] At least one of the units is irradiated with a laser pulse to change the state of the unit.

[0020] In one embodiment, irradiating at least one of the units with a laser pulse includes:

[0021] At least one of the units is irradiated with a first laser pulse, causing the unit irradiated by the first laser pulse to become crystalline; at least one of the units is irradiated with a second laser pulse, causing the unit irradiated by the first laser pulse to become an intermediate state, wherein the refractive index of the intermediate state unit is between the refractive index of the crystalline unit and the refractive index of the amorphous unit; the first laser pulse and the second laser pulse have different energies.

[0022] The main technical effects achieved by the embodiments of this application are:

[0023] The on-chip optical element and its fabrication method provided in this application embodiment, as well as the integrated optical element, have a phase change material layer in the modulation structure of the on-chip optical element that is a continuous film layer, and the state of the phase change material can be switched between multiple states. This allows for the control of the state of multiple units in the phase change material layer to achieve various functions of the on-chip optical element. In other words, reconstruction can be achieved without changing the structure of the on-chip optical element, resulting in a wider range of applications. Since the input coupling waveguide and the output coupling waveguide are located on the side of the modulation structure, the light rays incident on the modulation junction through the input coupling waveguide propagate in a direction parallel to the surface of the phase change material layer. The on-chip optical element can be applied to diffractive neural networks, on-chip scattering optical devices, on-chip diffractive optical devices, on-chip refractive optical devices, etc., offering greater application flexibility. Attached Figure Description

[0024] Figure 1 This is a three-dimensional structural schematic diagram of an on-chip optical element provided in an exemplary embodiment of this application;

[0025] Figure 2 This is a top view of an on-chip optical element provided in an exemplary embodiment of this application;

[0026] Figure 3 This is a partial structural cross-sectional view of an on-chip optical element provided in an exemplary embodiment of this application;

[0027] Figure 4 This is a partial structural cross-sectional view of an on-chip optical element provided in another exemplary embodiment of this application;

[0028] Figure 5 This is a top view of an on-chip optical element provided in another exemplary embodiment of this application;

[0029] Figures 6 to 9 Schematic diagrams of different on-chip optical elements provided in embodiments of this application;

[0030] Figure 10 This is a graph showing the relationship between the refractive index and extinction coefficient of Sb2Se3 in different states and the wavelength of light, provided in an exemplary embodiment of this application.

[0031] Figure 11 This is a flowchart of a method for fabricating an on-chip optical element provided in an exemplary embodiment of this application. Specific Implementation

[0032] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0033] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0034] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0035] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0036] This application provides an on-chip optical element. For example... Figure 1 and Figure 2 As shown, the on-chip optical element includes a substrate 10, an input coupling waveguide 20, a modulation structure 30, and an output coupling waveguide 40 located on the substrate 10.

[0037] like Figure 3 and Figure 4 As shown, the modulation structure 30 includes a phase change material layer 31 located on the substrate 10. The phase change material layer 31 is a continuous film layer, and it includes multiple units 311, with at least two units 311 having different refractive indices. The term "continuous film layer" means that the phase change material layer is a single, unpatterned film layer. See again. Figure 1 and Figure 2The input coupling waveguide 20 and the output coupling waveguide 40 are respectively located on the side of the modulation structure 30, so that the light rays incident on the modulation structure 30 through the input coupling waveguide 20 propagate in a direction parallel to the surface of the phase change material layer 31.

[0038] The on-chip optical element provided in this application embodiment has a continuous phase change material layer in its modulation structure, and the state of the phase change material can be switched between multiple states. This allows for the control of the state of multiple units in the phase change material layer to achieve various functions of the on-chip optical element. In other words, reconstruction can be achieved without changing the structure of the on-chip optical element, resulting in a wider range of applications. Since the input coupling waveguide and the output coupling waveguide are located on the side of the modulation structure, the light rays incident on the modulation junction through the input coupling waveguide propagate in a direction parallel to the surface of the phase change material layer. The on-chip optical element can be applied to diffractive neural networks, on-chip scattering optical devices, on-chip diffractive optical devices, on-chip refractive optical devices, etc., offering greater application flexibility.

[0039] In one embodiment, the states of the multiple units 311 of the phase change material layer 31 include crystalline, amorphous, and intermediate states between the crystalline and amorphous states. The refractive index of the intermediate state unit is between that of the crystalline unit and the amorphous unit. The transmittance of the units 311 in different states of the phase change material layer 31 varies, resulting in different phase shifts when light passes through the units 311. This allows the on-chip optical element to modulate light. By setting the states of the multiple units of the phase change material layer to include crystalline, amorphous, and intermediate states, the modulation of light by the on-chip optical element can be made more precise.

[0040] Furthermore, the states of the plurality of units 311 include multiple intermediate states, and the refractive index of the units 311 in different intermediate states is different. This can further improve the finer modulation of light by the on-chip optical elements.

[0041] In one embodiment, the substrate 10 is an SOI (Silicon On Insulator) substrate, or it may be a lithium slag substrate, or a silicon dioxide substrate. Figure 1 In the embodiment shown, the substrate 10 is an SOI substrate, comprising two silicon film layers 11 and a silicon dioxide film layer 12 located between the two silicon film layers 11.

[0042] In one embodiment, such as Figure 2 and Figure 5 As shown, the orthographic projection of the modulation structure 30 onto the substrate 10 is rectangular. The modulation structure 30 includes four sides, and the input coupling waveguide 20 and the output coupling waveguide 40 are located outside the different sides of the modulation structure 30. Figure 2In the embodiment shown, the input coupling waveguide 20 and the output coupling waveguide 40 are located on the outer sides of two opposite sides of the modulation structure 30. Figure 5 In the embodiment shown, the input coupling waveguide 20 and the output coupling waveguide 40 are located on the outer sides of two adjacent sides of the modulation structure 30.

[0043] In one embodiment, such as Figure 3 As shown, the phase change material layer 31 is in direct contact with the substrate 10. Light incident through the input coupling waveguide 20 propagates to the modulation structure 30, where the modulation structure 30 directly modulates the light. In this embodiment, the modulation structure 30 has a relatively simple structure.

[0044] Furthermore, the thickness of the phase change material layer 31 ranges from 200 nm to 400 nm. This configuration allows the phase change material layer 31 to modulate light more effectively. In some embodiments, the thickness of the phase change material layer 31 can be 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, etc.

[0045] In another embodiment, such as Figure 4 As shown, the modulation structure 30 further includes a waveguide structure layer 32 located between the substrate 10 and the phase change material layer 31, with the waveguide structure layer 32 in direct contact with the phase change material layer 31. With this configuration, light incident through the input coupling waveguide 20 propagates to the waveguide structure layer 32, where the phase change material layer 31 modulates the evanescent wave, causing changes in the amplitude and phase of the light. In some embodiments, the waveguide structure layer 32 can be a planar waveguide structure or other types of waveguide structures.

[0046] Furthermore, the thickness of the phase change material layer 31 ranges from 10 nm to 50 nm. This configuration allows the phase change material layer 31 to modulate light more effectively. In some embodiments, the thickness of the phase change material layer 31 can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc.

[0047] In one embodiment, such as Figure 2 and Figure 5 As shown, the multiple units of the phase change material layer 31 are arranged in multiple rows and columns. This arrangement allows for a more diverse distribution of the refractive index of the phase change material layer 31, thereby enhancing the versatility of on-chip optical components.

[0048] In one embodiment, the orthographic projections of each unit 311 in the phase change material layer 31 onto the substrate 10 have the same shape and the same area. For example, the orthographic projections of each unit 311 onto the substrate 10 may be rectangular, circular, or other shapes. Figure 2 and Figure 5In the embodiment shown, the orthographic projection of each unit 311 onto the substrate 10 is rectangular.

[0049] In one embodiment, such as Figure 5 As shown, there is a gap between two adjacent units 311 in the same row and between two adjacent units 311 in the same column of the on-chip optical element. In other embodiments, there is no gap between two adjacent units 311 in the same row and between two adjacent units 311 in the same column of the on-chip optical element.

[0050] In this embodiment, when there is no gap between two adjacent units in the same row and two adjacent units in the same column of the on-chip optical element, different on-chip optical elements can be formed by adjusting the state of multiple units in the phase change material layer 31. Figures 6 to 9 This diagram illustrates different on-chip optical elements obtained by adjusting the states of multiple units in a phase change material layer. The black lines in the diagram represent waveguide arms.

[0051] In one embodiment, the phase change material layer comprises at least one of Ge2Sb2Te5 and Sb2Se3. The operating wavelength of on-chip optical elements is typically 1050nm or 1550nm. Both Ge2Sb2Te5 and Sb2Se3 have very low extinction coefficients in this operating wavelength range, which helps reduce light loss during propagation. Furthermore, the refractive index difference between different states of Ge2Sb2Te5 and Sb2Se3 is significant in this operating wavelength range, effectively enabling light modulation.

[0052] Preferably, the phase change material layer is made of Sb2Se3. Figure 10 This graph shows the relationship between the refractive index and extinction coefficient of Sb₂Se₃ in different states and the wavelength of light. Curve a represents the relationship between refractive index and wavelength for crystalline Sb₂Se₃, curve b represents the relationship between extinction coefficient and wavelength for crystalline Sb₂Se₃, curve c represents the relationship between refractive index and wavelength for amorphous Sb₂Se₃, and curve d represents the relationship between extinction coefficient and wavelength for amorphous Sb₂Se₃. Figure 10It can be seen that when the wavelength of light is 1050 nm, the refractive index of crystalline Sb₂Se₃ is 4.5, and that of amorphous Sb₂Se₃ is 3.3; when the wavelength of light is 1550 nm, the refractive index of crystalline Sb₂Se₃ is 4, and that of amorphous Sb₂Se₃ is 3.2; at wavelengths of 1050 nm and 1550 nm, the extinction coefficients of both crystalline and amorphous Sb₂Se₃ are close to zero. That is, at wavelengths of 1050 nm and 1550 nm, the difference in refractive index between crystalline and amorphous Sb₂Se₃ is significant, and their extinction coefficients are very small.

[0053] In one embodiment, the modulation structure further includes a protective layer located on the side of the phase change material layer away from the substrate, the orthographic projection of the protective layer onto the substrate covering the orthographic projection of the phase change material layer onto the substrate. The protective layer protects the phase change material layer from oxidation. In some embodiments, the protective layer is made of indium zinc oxide or indium tin oxide, which provides high laser transmittance and reduces laser loss when the phase change material layer is irradiated with a laser.

[0054] This application also provides a method for fabricating an on-chip optical element. For example... Figure 11 As shown, the preparation method includes the following steps 110 and 120.

[0055] In step 110, an intermediate structure is provided, the intermediate structure including a substrate, an input coupling waveguide, an output coupling waveguide and a modulation structure located on the substrate, the modulation structure including a phase change material layer, the input coupling waveguide and the output coupling waveguide being located on the side of the modulation structure respectively; the phase change material layer is a continuous film layer including multiple units, and the initial state of the phase change material layer is amorphous.

[0056] In one embodiment, when the modulation structure includes a waveguide structure layer, the fabrication process of the intermediate structure is as follows:

[0057] First, a waveguide structure layer, an input coupling waveguide, and an output coupling waveguide are formed on the substrate.

[0058] After this step, the resulting structure can be cleaned. In some embodiments, acetone, anhydrous ethanol, and deionized water can be used sequentially for cleaning.

[0059] Subsequently, a photoresist layer is formed, the photoresist layer having an opening in the region where the phase change material layer is to be formed, the opening exposing the waveguide structure layer.

[0060] In one embodiment, the step of forming the photoresist layer may include the following process: first, forming a full-surface photoresist thin film layer, the orthogonal projection of the photoresist thin film layer on the substrate covering the substrate; then, sequentially exposing, developing, and fixing the photoresist thin film layer to obtain the photoresist layer. The photoresist material can be a negative photoresist. The photoresist thin film layer can be formed using a spin coating process, for example, a photoresist spin coater can be used to first spin coat at a speed of 700 rad / s for 9 s, and then spin coat at a speed of 3000 rad / s for 40 s to obtain the photoresist thin film layer. After obtaining the photoresist thin film using the spin coating process, a drying process can be performed, with a drying temperature of 120°C and a drying time of 90 s. When exposing the photoresist thin film, a contact ultraviolet lithography machine can be used, with an exposure dose of 300 J / cm². After exposure, the obtained structure can be dried, with a drying temperature of 120°C and a drying time of 90 s. In the developing step, RD6 developer can be used, and the developing time can be 50 seconds. In the fixing step, deionized water can be used for fixing, and the fixing time can be 60 seconds.

[0061] Subsequently, a phase change material layer is formed, which covers the opening in the photoresist layer.

[0062] In this embodiment, a magnetron sputtering device can be used to form the phase change material layer, and the vacuum degree of the coating chamber of the magnetron sputtering device can be 3×10⁻⁶. -4 The pressure of the coating chamber is 0.8 Pa, the argon flow rate is 30 sccm, the radio frequency power is 30 W, the sputtering time is 100 s, the sputtering rate is 3 angstroms / s, and the thickness of the final phase change material layer is 30 nm.

[0063] The photoresist layer is then removed.

[0064] The photoresist layer can be removed using a microwave plasma stripper. The parameters for the microwave plasma stripper can be set as follows: power 300W, argon flow rate 280sccm, oxygen flow rate 20sccm, and time 30s. After removing the photoresist layer, the resulting structure can be cleaned. The cleaning process is as follows: the obtained structure is first placed in a petri dish containing acetone, and then the petri dish is placed in an ultrasonic cleaner. The parameters for the ultrasonic cleaner can be set as follows: power 30W, and time 180s. After ultrasonic cleaning, it is cleaned again with anhydrous ethanol and deionized water.

[0065] In another embodiment, when the modulation structure comprises only a phase change material layer, the preparation process of the intermediate structure is as follows:

[0066] First, an input coupling waveguide and an output coupling waveguide are formed on the substrate.

[0067] After this step, the resulting structure can be cleaned. In some embodiments, acetone, anhydrous ethanol, and deionized water can be used sequentially for cleaning.

[0068] Subsequently, a photoresist layer is formed, the photoresist layer having openings in the areas where the phase change material layer is to be formed.

[0069] For specific details regarding the steps of forming the photoresist layer, please refer to the above embodiments, and they will not be repeated here.

[0070] Subsequently, a phase change material layer is formed, which covers the opening in the photoresist layer.

[0071] For specific details regarding the steps of forming the phase change material layer, please refer to the above embodiments, and will not be repeated here.

[0072] The photoresist layer is then removed.

[0073] For specific details regarding the step of removing the photoresist layer, please refer to the above embodiments, and will not be repeated here.

[0074] In step 120, at least one of the units is irradiated with a laser pulse to change the state of the unit.

[0075] In one embodiment, the step of irradiating at least one of the units with a laser pulse includes the following process: irradiating at least one of the units with a first laser pulse to make the state of the unit irradiated by the first laser pulse crystalline; irradiating at least one of the units with a second laser pulse to make the state of the unit irradiated by the first laser pulse intermediate, wherein the refractive index of the intermediate state unit is between the refractive index of the crystalline unit and the refractive index of the amorphous unit; the first laser pulse and the second laser pulse have different energies.

[0076] By controlling the number of laser pulses irradiating the cells, the energy of the laser pulses can be precisely controlled, thereby allowing for precise adjustment of the cell's state. Before irradiating the cells of the phase change material layer with laser pulses, the required refractive index distribution of the phase change material layer can be determined based on the data to be processed. Then, the number of laser pulses irradiating each cell can be determined based on this required refractive index distribution. Using laser pulses to change the cell's state is independent of photolithography and etching processes, significantly improving the flexibility of on-chip optical component reconstruction while reducing process errors and phase noise caused by photolithography and etching. Compared to methods using electrical pulses to change the cell's state, complex electrode wiring is not required, simplifying the structure.

[0077] In one embodiment, the step of irradiating at least one of the units with a second laser pulse to change the state of the unit irradiated by the first laser pulse to an intermediate state includes the following process: irradiating different units with multiple second laser pulses of different energies to obtain multiple units in different intermediate states.

[0078] In one embodiment, step 120 can be accomplished through the following process: controlling a light source to generate laser light, digitally modulating the laser light generated by the light source into laser pulses using an arbitrary waveform generator, and focusing the laser pulses onto the surface of the phase change material layer using an objective lens. A piezoelectric displacement stage can be used to control the horizontal movement of the intermediate structure to facilitate programming of different regions of the phase change material layer using laser pulses. The light source can be a 639nm laser diode, and the objective lens can be an 80x objective lens.

[0079] This application also provides an integrated optical element, which includes the on-chip optical element described in any of the above embodiments.

[0080] In one embodiment, the integrated optical element is used to process a single-frame image. The integrated optical element further includes a light source, a beam expander, a digital micromirror, a 4f optical system, and an objective lens. The laser light generated by the light source passes through the beam expander and is then incident on the digital micromirror, where image information is written into it. Afterward, it passes sequentially through the 4f optical system and the objective lens before entering the on-chip optical element. The wavelength of the laser light generated by the light source can be, for example, 1550 nm, 1050 nm, etc.

[0081] In one embodiment, the integrated optical element is used to process multimodal data. The integrated optical element further includes a controller, a light source, a beam splitter, multiple modulators, and multiple photodiodes. The beam splitter splits the input light provided by the light source into multiple sub-beams; the multiple modulators modulate each sub-beam to obtain modulated sub-beams; the on-chip optical element processes the optical data of the multiple modulated sub-beams to obtain multiple output sub-beams; each photodiode detects the output sub-beams and outputs an electrical signal; the controller is connected to the beam splitter, multiple modulators, and multiple photodiodes. The controller acquires the electrical signals output by each photodiode and processes the data, outputs modulation signals to each modulator, and adjusts the number and power of the beams split by the beam splitter.

[0082] In one embodiment, the integrated optical element can be an optical computing module, that is, the integrated optical element is applied in the field of optical computing.

[0083] It should be noted that the dimensions of layers and regions may be exaggerated in the accompanying drawings for clarity. Furthermore, it is understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on the other element, or there may be intermediate layers. Additionally, it is understood that when an element or layer is referred to as being "below" another element or layer, it can be directly below the other element, or there may be more than one intermediate layer or element. Furthermore, it is also understood that when a layer or element is referred to as being "between" two layers or two elements, it can be the only layer between the two layers or two elements, or there may be more than one intermediate layer or element. Similar reference numerals throughout indicate similar elements.

[0084] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0085] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. An on-chip optical element, characterized in that, The on-chip optical element includes: Substrate; The input coupling waveguide is located on the substrate; The output coupling waveguide is located on the substrate; A modulation structure; the modulation structure includes a phase change material layer located on the substrate, the phase change material layer being a continuous film layer comprising multiple units, at least two of the units having different refractive indices; the input coupling waveguide and the output coupling waveguide are respectively located on the side of the modulation structure, such that light rays incident on the modulation structure through the input coupling waveguide propagate in a direction parallel to the surface of the phase change material layer.

2. The on-chip optical element according to claim 1, characterized in that, The states of the plurality of units include crystalline state, amorphous state, and intermediate state between the crystalline state and the amorphous state, wherein the refractive index of the intermediate state unit is between the refractive index of the crystalline state unit and the refractive index of the amorphous state unit.

3. The on-chip optical element according to claim 1, characterized in that, The phase change material layer is in direct contact with the substrate; the thickness of the phase change material layer ranges from 200 nm to 400 nm.

4. The on-chip optical element according to claim 1, characterized in that, The modulation structure further includes a waveguide structure layer located between the substrate and the phase change material layer, the waveguide structure layer being in direct contact with the phase change material layer; the thickness of the phase change material layer is in the range of 10 nm to 50 nm.

5. The on-chip optical element according to claim 1, characterized in that, The multiple units are arranged in multiple rows and columns.

6. The on-chip optical element according to claim 1, characterized in that, The phase change material layer is made of at least one of Ge2Sb2Te5 and Sb2Se3.

7. The on-chip optical element according to claim 1, characterized in that, The modulation structure also includes a protective layer located on the side of the phase change material layer away from the substrate.

8. An integrated optical element, characterized in that, The integrated optical element includes the on-chip optical element as described in any one of claims 1 to 7.

9. A method for fabricating an on-chip optical element, characterized in that, The preparation method includes: An intermediate structure is provided, the intermediate structure including a substrate, an input coupling waveguide, an output coupling waveguide and a modulation structure located on the substrate, the modulation structure including a phase change material layer, the input coupling waveguide and the output coupling waveguide being located on the side of the modulation structure respectively; the phase change material layer is a continuous film layer including multiple units, and the initial state of the phase change material layer is amorphous; At least one of the units is irradiated with a laser pulse to change the state of the unit.

10. The method for fabricating an on-chip optical element according to claim 9, characterized in that, The step of irradiating at least one of the units with a laser pulse includes: At least one of the units is irradiated with a first laser pulse, causing the unit irradiated by the first laser pulse to become crystalline; at least one of the units is irradiated with a second laser pulse, causing the unit irradiated by the first laser pulse to become an intermediate state, wherein the refractive index of the intermediate state unit is between the refractive index of the crystalline unit and the refractive index of the amorphous unit; the first laser pulse and the second laser pulse have different energies.

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