Photonic crystal and preparation method thereof

Abstract

The invention discloses a photonic crystal and a preparation method thereof. According to an exemplary embodiment, the preparation method of the photonic crystal comprises the following steps: depositing a protective layer on a grating; depositing a phase change material film on the protective layer to obtain a photonic crystal; the photonic crystal is heated to convert the resonance position of the photonic crystal. According to the preparation technology disclosed by the invention, the light-substance interaction enhancement advantage of the plasmon continuous domain bound state (BIC) is fully utilized, the resonance position of the metasurface structure can be regulated and controlled by virtue of the dynamic adjustable function of the phase change material, the regulation and control range can cover different wavelength intervals and different incident angles at the same time, and the preparation efficiency is improved. Meanwhile, the method also has the outstanding advantages of simplicity and convenience in operation and good universality to a material system.

Description

Technical Field

[0001] This application relates to the field of laser technology, and more specifically, various exemplary embodiments relate to photonic crystals and methods for preparing photonic crystals. Background Technology

[0002] Metasurfaces are two-dimensional planar functional materials composed of a series of precisely designed subwavelength artificial structural units arranged periodically or aperiodically. Their thickness is typically much smaller than the operating wavelength, representing a key technological advancement in the evolution of metamaterials from three-dimensional bulk structures to two-dimensional planar structures. Unlike natural materials that rely on the inherent physical properties of their atoms and molecules to control electromagnetic waves, metasurfaces, through artificially designed dimensions, morphology, rotation angles, spatial arrangements, and materials, overcome the inherent limitations of natural materials in electromagnetic response. They can control key parameters such as amplitude, phase, polarization state, and propagation direction of electromagnetic waves across the entire spectrum, including visible light, infrared, microwaves, terahertz, and millimeter waves.

[0003] Compared to traditional optical manipulation methods, the two-dimensional planar nature of metasurfaces allows their thickness to be compressed to the nanometer scale in the optical band, and even in the microwave or terahertz band. Metasurfaces enable the fabrication of miniaturized, lightweight, and integrated devices, providing a new path for the miniaturization, arraying, and multifunctionalization of electromagnetic wave manipulation technology. With the continuous advancement of micro-nano fabrication technology, metasurfaces have become a research hotspot in the interdisciplinary fields of optical engineering, electromagnetics, and materials science. Furthermore, metasurfaces have demonstrated enormous application potential in emerging fields such as biosensing, quantum communication, and energy harvesting, becoming one of the core supporting materials driving next-generation technological innovation. Summary of the Invention

[0004] The subject matter of the independent claims is provided according to several aspects. Further aspects are defined in the dependent claims. Embodiments that do not fall within the scope of the claims should be interpreted as examples that aid in understanding this disclosure.

[0005] According to a first aspect of this disclosure, a method for preparing a photonic crystal is provided, which may include: depositing a protective layer on a grating; depositing a phase change material thin film on the protective layer to obtain a photonic crystal; and heating the photonic crystal to convert the resonant position of the photonic crystal.

[0006] According to a second aspect of this disclosure, a photonic crystal is provided, which may include: a substrate; a first thin film formed on the substrate; a grating metasurface formed on the first thin film; a protective layer formed on the grating metasurface; and a phase change material thin film formed on the protective layer. Attached Figure Description

[0007] Figure 1A schematic flowchart illustrating a photonic crystal fabrication method according to an exemplary embodiment of the present disclosure is shown.

[0008] Figure 2 A schematic diagram illustrating the changes in photonic crystal structure according to exemplary embodiments of the present disclosure;

[0009] Figure 3 A schematic diagram of a metal grating structure according to an exemplary embodiment of the present disclosure is shown;

[0010] Figure 4 A schematic diagram showing the surface height of a metal grating structure according to an exemplary embodiment of the present disclosure;

[0011] Figure 5A A schematic diagram of the surface of a photonic crystal before heating, according to an exemplary embodiment of the present disclosure;

[0012] Figure 5B A schematic diagram of the surface of a photonic crystal after heating, according to an exemplary embodiment of the present disclosure;

[0013] Figure 6 An example block diagram of an example optical device according to an exemplary embodiment of the present disclosure is shown.

[0014] The same or substantially the same elements, operations, and steps shown in the various figures may be indicated by the same reference numerals. For clarity, not every element, operation, or step is shown in every figure. Detailed Implementation

[0015] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. It should be understood that this disclosure should not be construed as limiting to the exemplary embodiments described herein, but rather that it can be implemented in various other forms, provided only for a more thorough and complete understanding of the present application. It should also be understood that the accompanying drawings are given by way of example only and are not intended to limit the precise form of the embodiments or to limit the scope of protection of the present application.

[0016] The following embodiments are exemplary. Although the specification refers to "a," "an," or "some" embodiments in various places, this does not necessarily mean that each reference refers to the same embodiment, or that a specific feature applies only to a single embodiment. Individual features of different embodiments may also be combined to provide other embodiments. Moreover, when specific features, structures, or characteristics are described in conjunction with embodiments, whether explicitly described or not, such features, structures, or characteristics will be applied to other embodiments to the extent that those skilled in the art possess the knowledge to do so. It should be understood that although terms such as "first" and "second" may be used to describe various elements, these elements should not be limited by these terms. These terms are merely used to distinguish one element from another.

[0017] In this disclosure, the terms "at least one of A or B", "at least one of A and B", and "A and / or B" mean [A], [B], or [A and B]. In this disclosure, "A, B, and / or C" means [A], [B], [C], [A and B], [A and C], [B and C], or [A, B, and C].

[0018] The core functions of traditional metasurfaces, such as wavefront manipulation of electromagnetic waves, polarization state conversion, precise beam focusing, directional beam deflection, and high-resolution holographic imaging, rely on their static geometry and intrinsic material properties. Therefore, their functional design requires parameter iteration through simulation or calculation before device fabrication, ultimately solidifying the optimal design scheme. This may involve specific geometric shapes, dimensional parameters, and specific substrate and structural material combinations. Once the device is fabricated using micro / nano fabrication processes, the metasurface forms an irreversible, fixed structure, and its optical properties are fixed. It can only achieve the specific functions designed for it within a preset single operating frequency band, under specific incident conditions, or under limited operating conditions, and cannot be adaptively adjusted according to the dynamic changes in actual application scenarios.

[0019] The inherently fixed fabrication characteristics of traditional metasurfaces result in a strong scene-dependent functionality. Their performance degrades drastically once deviated from pre-defined operating conditions, making them inflexible when facing complex and ever-changing application requirements. To utilize metasurface technology in different scenarios, engineers must either fabricate new devices or employ strategies such as stacking or arraying multiple devices. However, these strategies not only increase system size, weight, and manufacturing costs but also introduce additional problems such as mechanical wear and switching delays. This limitation makes it difficult for traditional metasurfaces to meet the flexible application scenarios requiring dynamic tunability, multifunctional integration, and adaptive response.

[0020] To address the problems existing in the prior art, this disclosure proposes a dynamically tunable plasmonic continuous domain bound state (BIC) fabrication technique based on phase change materials. This technique fully utilizes the enhanced light-matter interaction inherent in BICs and leverages the dynamically tunable function of phase change materials to achieve control over the resonant position of the metasurface structure. The control range can simultaneously cover different wavelength ranges and different incident angles. Photonic crystals with BIC grating structures prepared using this technique only require a simple external stimulus—heating—to trigger the phase transition process of the material, thereby achieving dynamic switching of the photonic crystal's own state. This state switching directly alters the structural parameters of the internal BIC grating, ultimately achieving dynamic control over the resonant position and BIC angle of the photonic crystal. This characteristic not only effectively overcomes the shortcomings of traditional photonic crystal metasurface structures that are fixed and can only achieve static control, but also ensures that the photonic crystal maintains stable performance over a wide range of incident angles. In addition, the preparation process disclosed herein has the outstanding advantages of being easy to operate and having good universality to material systems.

[0021] Figure 1 A schematic flowchart of a photonic crystal fabrication method 100 according to an exemplary embodiment of the present disclosure is shown. The flowchart clearly presents the step-by-step construction process from a base substrate to a complete photonic crystal structure. Optimized process parameters and operational details for each step are given in the exemplary embodiment. It should be noted that these details are only for clear description purposes, and those skilled in the art can fine-tune the specific operational details when using the scheme of the present disclosure. Figure 2 This diagram illustrates the structural changes of a photonic crystal during the fabrication process of an exemplary embodiment of this disclosure. It visually demonstrates the stacking, patterning, and morphological evolution of material layers at different process stages. Those skilled in the art will understand that a photonic crystal with a pre-defined optical function and a complete structure can be referred to as a finished product, while a photonic crystal that has not yet completed all process steps and has only formed a partial structure can be referred to as a semi-finished product. For ease of explanation and not for limiting the disclosure, the aforementioned semi-finished or finished products may also be collectively referred to as samples in this disclosure. This terminology is merely for concise expression and does not affect the limitations on the fabrication process and structural characteristics. The following, in conjunction with… Figure 1 as well as Figure 2 The preparation method of this disclosure and the structure of the photonic crystal obtained by the preparation method are described in detail.

[0022] See Figure 1In step 110 of preparation method 100, a substrate for the photonic crystal can be prepared first. In some embodiments, the substrate can be a high-purity pure silicon substrate. Before use, the pure silicon substrate can be cleaned to remove organic contaminants, oxide layers, or microparticle impurities from the surface. Specifically, the pure silicon substrate can first be immersed in a high-purity acetone solution for 5 minutes to clean it, utilizing the strong organic solvent properties of acetone to efficiently dissolve oil, resin, and other organic impurities adhering to the substrate surface. Then, the cleaned substrate is successively immersed in an isopropanol solution and then in pure water for 5 minutes each to remove residual acetone and wash away various impurity particles, thus ensuring that the substrate surface is free of residual contaminants. After cleaning, the substrate can be removed and dried, and then placed on a high-precision hot plate for baking. The temperature of the hot plate can be adjusted to 120°C, and the substrate can be baked at a constant temperature for 30 minutes to remove water molecules and trace amounts of residual solvent adsorbed on the substrate surface, ensuring that the substrate surface is dry and clean. Through step 110, a final form can be formed as shown in the image. Figure 2 The substrate structure shown in 210, as previously described, can be a silicon substrate.

[0023] Next, in step 120, a first thin film material for the reflective layer can be prepared on the substrate using physical deposition technology. In some embodiments, the first thin film material can be a metal thin film, specifically gold (Au), silver (Ag), or aluminum (Al), with gold being the preferred material for preparing the first thin film. For clarity, this disclosure uses gold as an example for specific illustration. In some embodiments, a gold (Au) target can be deposited using an electron beam metal deposition system. This system uses a high-energy electron beam to bombard a high-purity gold (Au) target in a high-vacuum environment. During this process, the kinetic energy of the electron beam is converted into heat energy, causing the local temperature of the target to rise rapidly to the evaporation temperature, thereby causing gold atoms or molecules to escape rapidly from the target surface. The escaped gold atoms or molecules are then uniformly deposited onto the pretreated substrate surface. By controlling the deposition time and electron beam power, a first metal thin film meeting the target requirements can be formed. Figure 2As shown in Figure 220, after completing this preparation step, the semi-finished photonic crystal may include a bottom substrate and a first thin film material tightly covering the substrate. Here, the first thin film material can be a metal thin film, specifically a gold thin film, and the thickness of the metal thin film can be controlled to be 50 nanometers. In some embodiments, in order to solve the problems of film peeling and cracking that may occur during long-term use due to poor natural adhesion between gold and silicon substrate, a titanium metal layer can be grown first by metal evaporation technology before growing the gold thin film to form a strong chemical bond with both the silicon substrate and the gold thin film. Its thickness can be, for example, 5 nanometers. In this case, a composite metal thin film structure consisting of a 5 nm thick titanium transition layer and a 50 nm thick gold functional layer can be deposited using an electron beam evaporation system. Compared with a pure gold thin film, this composite structure has the effect of improving the bonding strength between the thin film and the substrate.

[0024] In step 130, to accurately fabricate the patterned structure of the second thin film material on the formed first thin film material, a layer of photoresist can be first deposited on the first thin film material. In some embodiments, the photoresist can be polymethyl methacrylate (PMMA). In some embodiments, PMMA photoresist can be prepared on a gold thin film using a spin-coating method. Specifically, a 495-A5 (4000r, 60s) 205nm PMMA photoresist can be spin-coated onto the gold thin film, where 495-A5 is the photoresist type, 4000r is the spin-coating speed of 4000 rpm, and 60s is the spin-coating duration. These two parameters are process parameters for spin-coating to prepare the film, and 205nm is the wavelength for detecting the film thickness. The patterned structure of the second thin film material is formed through step 130. Figure 2 The semi-finished photonic crystal shown in 230 can include, from bottom to top, a substrate layer (which can be silicon), a first thin film material layer (which can be gold) and a photoresist layer. It can be seen that the layers are tightly bonded together and there are no obvious gaps.

[0025] In step 140, the sample formed above can be subjected to electron beam lithography (EBL) to expose a preset pattern of the second thin film material on the photoresist. This pattern can be the pattern of the grating structure of the finished photonic crystal. In some embodiments, an electron beam with an accelerating voltage of 10 kV can be used for exposure; during exposure, the electron beam can scan the photoresist surface along the preset grating pattern path, and the photoresist area irradiated by the electron beam undergoes chemical changes, laying the foundation for subsequent development and fixing processes. Figure 2 As shown in Figure 240, the photoresist layer of the semi-finished photonic crystal after exposure will form a specific pattern prototype. The chemical properties of the exposed area and the unexposed area will be significantly different, providing conditions for subsequent patterning.

[0026] Next, in step 145, the sample can be developed and fixed to remove areas of the photoresist exposed by the electron beam and ensure pattern stability, thereby converting the exposed pattern prototype into an actual physical pattern. In some embodiments, a developer suitable for PMMA photoresist can be selected, and the sample is immersed in the developer for 40 seconds for development; after development, the sample is transferred to a fixer and immersed for 30 seconds for fixing. The structure of the semi-finished photonic crystal after development and fixing is as follows... Figure 2 As shown in Figure 250, a physical groove structure that is completely consistent with the preset grating pattern is formed on the photoresist layer. This structure will serve as a template for the subsequent deposition of the second thin film.

[0027] In step 150, a second thin film can be deposited, which can constitute the functional body of the grating. In some embodiments, the grating patterned sample after development and fixing can be placed in an electron beam evaporation (EBD) system, and the same electron beam metal deposition technology as the first thin film can be used to deposit the film to form a uniform metal film. The material of the second metal film can also be gold, silver, or aluminum. In some embodiments, the material of the second metal film can be the same as that of the first metal film. For ease of explanation, gold will be used as the film material in the following description. The settings of parameters such as the vacuum environment and deposition power of the electron beam evaporation system can be consistent with those in step 120. In some embodiments, the thickness and width range of the deposited second metal film can be selected according to the designed grating period to ensure that the resonant wavelength of the photonic crystal meets the design requirements. For example, the thickness range of the metal film can be 40-70 nanometers, preferably 40 nanometers; the width range can be 150-170 nanometers. See also Figure 2 After the deposition of the second thin film, a second thin film material (e.g., a gold thin film) is formed in the exposed area of ​​the first thin film and on the top surface of the remaining photoresist protrusions. Those skilled in the art will understand that although the illustration only shows a second thin film material on the top surface of the photoresist, a second thin film material may also exist on the side of the photoresist during actual deposition. In this case, the semi-finished photonic crystal exhibits a complex structure with multiple superimposed layers.

[0028] Next, in step 160, the photoresist can be removed using a solvent extraction process, leaving only the second metal film deposited on the first thin film to form an independent grating array, thus obtaining a complete grating structure. In some embodiments, the obtained sample can be placed in a high-purity acetone solution for solvent extraction; during the solvent extraction process, the acetone solution can be stirred appropriately to accelerate the dissolution of the photoresist and ensure complete removal. Through the solvent extraction process, the photoresist and the second thin film material attached to the photoresist are removed, leaving only the second gold film deposited on the first gold film, forming a regularly arranged grating structure. Figure 2 As shown in Figure 270, the semi-finished photonic crystal consists only of a substrate (which can be silicon), a first thin film material (which can be gold), and a second thin film material (which can be gold) that forms the grating structure. At this point, the grating structure already possesses basic optical functions. Figure 3 A schematic diagram of a metal grating structure according to an exemplary embodiment of the present disclosure is shown. It can be seen that the prepared metal grating structure has a clear outline, good morphological features, and is arranged in a regular periodic pattern. The semi-finished crystal prepared in step 160 (i.e....) Figure 2 The grating structure formed on the surface of the 270 semi-finished crystal can be combined with... Figure 3 The structures shown are consistent. Figure 4 A schematic diagram showing the surface height of a metal grating structure according to an exemplary embodiment of the present disclosure is provided. It can be seen that the height of the metal grating is approximately 40 nm and is uniformly distributed, consistent with the original design target. The above observation results also demonstrate the good operability of the fabrication method of the present disclosure. In some embodiments, the semi-finished photonic crystal can be observed using an atomic force microscope (AFM) to obtain... Figure 3 or Figure 4 The schematic diagram shown illustrates how observing the sample during the preparation process ensures that the photonic crystal preparation process is executed correctly.

[0029] In step 170, a protective layer can be grown on the obtained sample to protect the metal grating structure. In some embodiments, silicon dioxide (SiO2) can be deposited on the semi-finished photonic crystal using inductively coupled plasma-enhanced chemical vapor deposition (ICPECVD) to obtain the protective layer. During the deposition operation, the ICPECVD system can be controlled at 80 degrees Celsius, and the SiO2 protective layer can be grown by controlling the runtime. In some embodiments, the runtime can be controlled to 15 seconds to grow the protective layer. Figure 2 As shown in Figure 280, after the protective layer is deposited, a dense protective layer is formed on both the second thin film material (the grating body) and the exposed surface of the first thin film material.

[0030] In step 180, a phase change material thin film can be grown on the protective layer. The introduction of the phase change material is the core of realizing the dynamically tunable characteristics of the photonic crystal, and the transition between its crystalline and amorphous states can significantly change the optical parameters of the photonic crystal. In some embodiments, the phase change material can be antimony trisulfide (Sb₂S₃). In some embodiments, the patterned sample with the protective layer can be placed in a magnetron sputtering (MS) system, and the phase change material thin film can be prepared using magnetron sputtering technology. Using magnetron sputtering technology, argon gas (Ar) is introduced into a vacuum chamber as the sputtering gas. The electromagnetic field generated by the radio frequency power supply causes electrons to collide with argon atoms, ionizing them into a large number of argon ions. These argon ions are accelerated under the influence of the electric field to bombard the Sb₂S₃ target material. After the target atoms are sputtered out, they are deposited on the sample surface to form a phase change material thin film. The operating conditions of the magnetron sputtering system can be set to an argon flow rate of 10 standard cubic centimeters per minute (sccm), a chamber pressure of 7 millitors (mtorr), and a sputtering RF power of 50 W. Under these conditions, phase change material thin films can be obtained by controlling the running time. In some embodiments, the running time can be 5 minutes and 21 seconds. Through step 180, the following can be obtained: Figure 2 The photonic crystal product or semi-finished product shown in 290 further has a uniformly covered phase change material film formed on the protective layer. In some embodiments, the thickness of the phase change material film can be 10 nm-25 nm, preferably 10 nm. After the addition of the phase change material, the resonance position of the grating structure will change significantly and become fixed, for example, it can be changed from the original 590 nm to 673-710 nm. Those skilled in the art will understand that the photonic crystal structure after the addition of the phase change material is the final structure of the photonic crystal obtained according to the preparation method of this disclosure, but the subsequent heating process can still dynamically adjust the resonance position of the grating structure by changing the crystal structure of the phase change material in the photonic crystal. Therefore, those skilled in the art will understand that... Figure 2 The photonic crystal shown in 290 can be referred to as a finished product or a semi-finished product.

[0031] Next, in step 190, the sample with a complete structure can be heated to trigger a crystalline transformation of the phase change material through thermal excitation, thereby achieving dynamic control of the resonance position. In some embodiments, the sample can be placed on the heating plate of a high-precision heating stage for heating. The temperature can be precisely controlled by the heating stage to ensure the stability and repeatability of the phase change process. The core purpose of heating is to precisely switch the phase change material between the amorphous, intermediate, and crystalline states, thereby achieving tunability of the resonance position. In some embodiments, the temperature of the heating stage can be set to 250°C. The sample can be heated on the 250°C hot plate for 1 minute, at which point the phase change material can transform from the amorphous state to the intermediate state, and the resonance position can be redshifted to approximately 732-760 nm. If the sample is heated on the 250°C hot plate for 3 minutes, the phase change material can transform from the amorphous state to the crystalline state, and the resonance position can be redshifted again to approximately 778-810 nm. In addition, in some embodiments, the temperature of the heating stage can be raised to more than 250°C to transform the crystalline phase change material back into an amorphous state, thereby bringing its resonance position back to the range of about 673-710nm and achieving cyclic control of the resonance position. Figure 5A The diagram shows the surface of the sample before heating. At this time, the phase change film material has not undergone phase change and is in a non-crystalline state. From the microscopic morphology, the surface presents a smooth state with uniformity and no obvious texture. Figure 5B The diagram shows the surface of the sample after it has been heated on a heating stage and transformed into a crystalline state. At this point, the phase change film material has undergone a complete phase change, and the surface forms obvious textures or crystal grain morphology, with the appearance of a chemical-level crystal domain structure. This change in microstructure is the fundamental reason for the change in its optical properties.

[0032] The grating structure disclosed herein, after incorporating a phase change material (10-25 nm thick), adjusts the resonant position from the original 590 nm to the range of 673-710 nm. When the phase change material is heated to an intermediate state, the resonant position can redshift to approximately 732-760 nm. Upon further heating and transformation into a crystalline state, the resonant position can redshift further to approximately 778-810 nm, exhibiting a significant tuning effect. During the transition of the phase change material from an amorphous to a crystalline state, the optical field localization capability of the photonic crystal is significantly enhanced, and the dispersion relation near the Γ point becomes smoother. This characteristic makes the continuous domain bound state (BIC) insensitive to changes in the incident light angle, greatly improving the flexibility of photonic crystal applications. Simultaneously, with the redshift of the resonant position after the phase transition, the BIC angle of the local optical field also expands from the original 1°-5° range to the 10°-15° range, enabling the photonic crystal to adapt to a wider range of incident angle conditions in practical applications. As can be seen, the preparation method disclosed herein, by cleverly combining phase change materials with grating structures, can achieve dynamic control of the BIC position and maintain stable local optical field characteristics over a large angle range. This successfully overcomes the inherent limitation of previous photonic crystal metasurfaces that could only statically control structural parameters, providing key technical support for the application of photonic crystals in dynamic optical devices.

[0033] Figure 6 A block diagram of an example optical device 600 according to an exemplary embodiment of the present disclosure is shown. This exemplary optical device, based on a dynamically tunable continuous-domain bound-state photonic crystal prepared according to the present disclosure, integrates functional modules such as signal input, processing, output, modulation, and monitoring, forming a complete functional system. (Reference) Figure 6 The optical device 600 may include an input unit 610, a photonic crystal 620, an output unit 630, a control unit 640, and a monitoring and feedback unit 650. These units can be connected via optimized optical paths or circuits. The photonic crystal 620 serves as the core functional carrier and optical field control core of the optical device. It can be fabricated using the methods described above and possesses dynamically tunable continuous-domain bound-state characteristics. It can flexibly adjust optical parameters according to actual needs and can serve as the functional basis for various high-performance optical devices such as lasers, sensors, and filters, providing the device with high-sensitivity and high-stability optical field control capabilities.

[0034] The input unit 610 serves as the entry point for signal or energy interaction between the device and external systems, enabling efficient coupling and preprocessing of external signals. The input unit 610 can receive various input signals, such as external pump energy (e.g., laser pumping), driving electrical signals, and incident light signals. Through built-in optical components (e.g., lenses, polarizers, filters), it achieves mode matching with the photonic crystal unit 620, ensuring compatibility between the input signal mode and the operating mode of the photonic crystal 620. Simultaneously, the input unit 610 can perform necessary preprocessing operations on the input signals, such as signal coupling, collimation, polarization adjustment, and wavelength filtering, removing noise components and optimizing signal quality. This allows external signals to enter the photonic crystal unit 620 efficiently and with low loss, participating in core optical processes (e.g., light field enhancement, resonant filtering, signal modulation).

[0035] Output unit 630 can serve as an external port for exporting the functional results of the device. It can optimize the optical signal or converted electrical signal processed by photonic crystal unit 620 to meet the interface requirements of external systems. Output unit 630 can have built-in suitable optical or electrical processing components, capable of performing mode conversion, signal amplification, waveform shaping, or filtering on the signal output by the photonic crystal, effectively reducing signal transmission loss and distortion, and ensuring that the strength, purity, and stability of the output signal meet application requirements.

[0036] The control unit 640 can be the core for dynamically adjusting the characteristics of the optical device 600, and can adjust the optical parameters of the photonic crystal according to actual needs. The control unit 640 can receive external commands (such as the target resonance wavelength set by the user) or the status signal output by the monitoring feedback unit 650, and change the key parameters of the photonic crystal unit 620 (such as the crystal state of the phase change material, the equivalent refractive index of the grating structure, etc.) through various control methods such as electro-optic effect, thermo-optic effect, magneto-optic effect, acousto-optic effect, or surface sensitive layer effect, thereby dynamically controlling the output characteristics of the device (such as output wavelength, light intensity, polarization state, etc.). In some embodiments, the control unit 640 can integrate a heating module, and by heating the dynamically tunable continuous domain bound state photonic crystal of this disclosure, the crystal state switching of the phase change material can be realized, thereby dynamically changing its resonance position.

[0037] The monitoring feedback unit 650 serves as the core for sensing and closed-loop control of the device's operating status. It monitors the device's operating status in real time, providing precise feedback signals to the control unit to ensure stable device operation. The monitoring feedback unit 650 can incorporate various high-precision sensors (such as optical power sensors, spectrometers, temperature sensors, and light field distribution detectors) to collect key operating status parameters of the photonic crystal unit 620 or the entire device in real time, including output optical power, operating wavelength, device temperature, light field distribution, spectral drift, and resonant frequency. Subsequently, the monitoring feedback unit 650 converts these physical state signals into processable electrical signals. After analysis and calibration by its internal signal processing module, these signals are fed back to the control unit 640, forming a closed-loop control circuit. This allows the control unit to adjust its control strategy in real time based on the actual operating status, compensating for signal drift or external interference. Simultaneously, the monitoring feedback unit 650 can also transmit key status signals to external systems for status warnings and fault diagnosis, improving the device's reliability and maintainability.

[0038] In this disclosure, although the steps of operation are described in a specific order, this should not be construed as requiring such operations to be performed in the specific order or sequence shown, or requiring the performance of all shown operations to obtain the desired result. In some cases, changing the order of steps or omitting certain steps is advantageous. Similarly, although several specific implementation details are included in the foregoing discussion, these details should not be construed as limiting the scope of this disclosure, but rather as descriptions of features specific to particular embodiments. Certain features described in the context of a single embodiment may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0039] The basic principles of this disclosure have been described above in conjunction with embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0040] The block diagrams of devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0041] Furthermore, in the apparatus, devices, and methods disclosed herein, the components or steps can be disassembled and / or recombined. Such disassembly and / or recombination should be considered equivalent solutions to this disclosure.

[0042] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0043] The above description has been given for illustrative and descriptive purposes and is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

[0044] Although the subject matter has been described in language specific to structural features and / or methodological actions, it should be understood that the subject matter defined in the appended claims is not limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as examples of implementing the claims.

Claims

1. A method for preparing a photonic crystal, comprising: Deposit a protective layer on the grating; A photonic crystal is obtained by depositing a phase change material thin film on the protective layer; The photonic crystal is heated to change the resonant position of the photonic crystal.

2. The photonic crystal fabrication method according to claim 1, wherein, Depositing a protective layer on a grating includes: depositing silicon dioxide on the grating by inductively coupled plasma-enhanced chemical vapor deposition to form a protective layer on the grating.

3. The photonic crystal fabrication method according to claim 1, wherein, Depositing a phase change material thin film on the protective layer to obtain a photonic crystal includes: depositing antimony trisulfide on a grating on which the protective layer has been deposited using a magnetron sputtering system to obtain a photonic crystal.

4. The photonic crystal fabrication method according to claim 1, wherein, Heating the photonic crystal to change its resonant position includes: The photonic crystal is heated for a first time to obtain an intermediate state photonic crystal with a first resonant position, or the photonic crystal is heated for a second time to obtain a crystalline state photonic crystal with a second resonant position. The first resonance position is between 732-760nm; the second resonance position is between 778nm-810nm; and before heating, the resonance position of the photonic crystal is between 673nm-710nm.

5. The photonic crystal fabrication method according to claim 1, further comprising: A first thin film material is deposited on a substrate; Photoresist is applied onto the first thin film material; Forming a grating pattern on the photoresist; A second thin film material is used to form a thin film on the pattern of the grating to obtain a semi-finished grating; The semi-finished grating is melted and removed to obtain the grating.

6. The photonic crystal fabrication method as described in claim 5, wherein, The formation of a grating pattern on photoresist includes exposure using electron beam lithography to form a grating pattern on the photoresist; The method of forming a thin film on the pattern of the grating using a second thin film material to obtain a semi-finished grating includes forming a thin film on the pattern of the grating by distilling the second thin film material using an electron beam metal coating system to obtain a semi-finished grating. The process of dissolving and removing the semi-finished grating to obtain the grating includes placing the semi-finished grating in acetone for dissolution and removal to obtain the grating.

7. The method for preparing a photonic crystal as described in claim 5 or 6, wherein, The substrate is made of pure silicon; The first thin film material includes at least one of gold, titanium, silver, or aluminum; The second thin film material includes at least one of gold, silver, or aluminum; The photoresist is polymethyl methacrylate photoresist.

8. A photonic crystal, comprising: Substrate; A thin film layer is formed on the substrate; A grating metasurface is formed on the thin film layer; A protective layer is formed on the grating metasurface; as well as A phase change material thin film is formed on the protective layer.

9. The photonic crystal as described in claim 8, wherein, The thin film layer comprises 5nm titanium and 50nm gold; The protective layer comprises 10 nm of silicon dioxide; The phase change material film includes 10 nm of antimony trisulfide.

10. An optical device comprising the photonic crystal as described in claim 8 or 9.

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