A preparation method and product of laser erasable frequency selective surface

Abstract

The present invention belongs to the technical field related to electromagnetic structures and laser processing, and discloses a method for preparing a laser-erasable frequency selective surface, comprising: depositing a high-resistance memory phase change film layer and a transmittance protective layer on the surface of an insulating substrate; reversibly inducing a phase change in the deposited memory phase change film layer by pulsed lasers with different resistance phase change parameters; and producing the desired frequency selective surface product by direct writing with laser scanning or mask projection processing. Through the present invention, the preparation, modification, and reconstruction functions of the frequency selective surface can be realized in an efficient, controllable, and reliable manner. The product produced has non-volatility and strong stability, and the resonant unit graphic size and array can be repeatedly modified to ensure the preparation accuracy and quality of the frequency selective surface for complex curved surfaces. At the same time, the resonant frequency and transmission passband of the frequency selective surface can be changed over a large range. The preparation method also has the advantages of being pollution-free and causing no damage to the surface of the insulating substrate.

Description

Technical Field

[0001] The present invention belongs to the technical field related to electromagnetic structures and laser processing, and more specifically, relates to a preparation method and product of a laser-erasable frequency selective surface. Background Art

[0002] A frequency selective surface (FSS) is a single-screen or multi-screen periodic array structure composed of a large number of resonant units. It is composed of periodically arranged metal patch units or periodically arranged aperture units on a metal screen. Its basic electromagnetic characteristics are characterized by its selectivity for electromagnetic waves of different operating frequencies, polarization states, and incident angles. Radomes loaded with FSSs are widely used in stealth applications for fighter aircraft, satellites, and shipborne radar antenna covers because they can significantly reduce the radar cross-section of a vehicle, effectively lowering the probability of detection by enemy radar. FSSs can be divided into four basic types based on their transmission performance: bandpass, bandstop, highpass, and lowpass.

[0003] Currently, the mainstream method for preparing FSS is to load a metal film layer on an insulating substrate and prepare a resonant unit pattern array through photolithography or laser etching technology. For the former, early patents such as CN108123228B, US5650249A, and CN110247192B all disclose methods for preparing curved frequency selective surface arrays based on photolithography technology. This technology removes the metal film layer through mask exposure and development and etching to prepare a unit pattern array. However, this method requires the preparation of a mask shell that is conformal to the substrate during the process of making an FSS with complex surfaces. This method has high cost, poor precision, and a long production cycle. At the same time, the preparation process also generates chemical waste liquids that pollute the working environment.

[0004] Regarding the latter, early patents such as CN110587143A and CN108767484A disclose methods for preparing curved FSS based on laser etching. These methods apply a high-power laser beam directly to a metal layer, removing the metal film layer by ablation to create an array of resonant unit patterns. This technology can produce FSS with complex curves without the need for a mask and without causing chemical contamination. However, it cannot avoid damage to the insulating substrate surface and the contamination of optical lenses and the surrounding environment by ablation dust and smoke. Furthermore, during the laser etching of tens of thousands of unit patterns, if the etched dimensional accuracy and quality do not meet design requirements, they cannot be repaired and must be scrapped, resulting in increased production costs and reduced production efficiency.

[0005] Therefore, the existing frequency selective surface preparation process has the following major defects or deficiencies: First, its preparation accuracy needs to be further improved, and it is difficult to ensure that the dielectric substrate under the metal layer is not damaged during the preparation process; second, this type of process has a low fault tolerance during the preparation process, and once a mistake occurs, it cannot be repaired. At the same time, the preparation process will cause pollution problems such as smoke, dust, and chemical liquids. Third, more importantly, regardless of whether the FSS is prepared by photolithography or laser etching, once the preparation is completed, its operating frequency point is single, the frequency selection performance cannot be changed, and there is a lack of flexibility. Consequently, the resonant frequency point and transmission passband cannot be changed. That is, after the production is completed, the shape, size, and arrangement of the resonant unit cannot be changed. Summary of the Invention

[0006] In response to the above-mentioned deficiencies or needs in the prior art, the present invention aims to provide a method and product for preparing a laser-erasable frequency selective surface, wherein the method cleverly utilizes memory phase change materials to achieve reversible phase change characteristics under pulsed laser induction conditions. Pulsed lasers of varying power densities are used to reversibly induce phase change in the memory phase change film layer deposited on the insulating substrate, thereby enabling efficient and controllable high-precision, high-quality preparation of the frequency selective surface and reconstruction of its frequency selection characteristics. Furthermore, the metal-free resonant unit array constructed by the present invention can exist stably for a long time under passive conditions, possessing greater frequency conversion stability and resistance to external interference. Furthermore, when the array size and shape need to be changed, a pulsed laser of appropriate power density is used to induce phase change again, enabling smooth changes in the resonant frequency and transmission characteristics, thereby achieving the "erasing" function for the FSS pattern array.

[0007] To achieve the above object, according to one aspect of the present invention, a method for preparing a laser-erasable frequency selective surface is provided, characterized in that the method comprises the following steps:

[0008] Step 1: Using thin film deposition technology, a high-resistance memory phase change film layer and a transmissive protective layer are sequentially deposited on the surface of the insulating substrate;

[0009] Step 2: using a laser scanning method to allow a pulsed laser to pass through the transmissive protective layer to selectively irradiate the high-resistance memory phase change film layer, and causing the temperature of the irradiated area to reach the phase change threshold temperature, thereby forming a patterned low-resistance phase change film layer array structure; or

[0010] First, the entire high-resistance memory phase change film layer is converted into a low-resistance film layer, and then a pulsed laser is passed through the transmissive protective layer to selectively irradiate the low-resistance film layer, and the temperature of the irradiated area reaches the melting threshold temperature and is rapidly cooled, thereby forming a patterned high-resistance phase change film layer array structure;

[0011] Step three: Use laser scanning to directly write the patch-type resonant unit pattern array composed of the patterned low-resistance phase change film layer array structure, or use laser scanning to directly write the slot-type resonant unit pattern array composed of the patterned high-resistance phase change film layer array structure, thereby obtaining a frequency selective surface with a stable resonant frequency and transmission passband.

[0012] As a further preference, in step one, the high-resistance memory phase change film layer is preferably a pseudo-binary alloy material composed of germanium telluride (GeTe) and antimony telluride (Sb2Te3), and can be selected from any one or a combination of the following substances: GeTe, Ge2Sb2Te5, Ge1Sb2Te4, Ge1Sb4Te7.

[0013] As further preferred, in step 1, the transmissive protective layer is preferably a passive material having a transmissive wavelength in the range of 300 nm to 1200 nm, and is further preferably SiO 2 .

[0014] As a further preferred embodiment, in step 2, the laser used in the laser scanning method is preferably a pulsed laser with a wavelength in the range of 300nm to 1200nm and a pulse width of no more than nanoseconds; after being focused by the three-dimensional laser scanning system, it is preferred that a power density of 1×10 17 W / m 3 to 10×10 17 W / m 3 , the focused light spot has different shapes such as circular, square, linear, etc.

[0015] As a further preferred embodiment, in step 2, the pulse laser preferably has the following low-resistance phase transition induction parameters: pulse width is no more than nanoseconds, power density is 1×10 17 W / m 3 to 7.5×10 17 W / m 3 , and accordingly convert the irradiated area of ​​the high-resistance memory phase change film layer into a low-resistance state; or the pulse laser preferably has the following high-resistance phase change inducing parameters: pulse width is no more than nanoseconds, power density is 8×10 17 W / m 3 to 10×10 17 W / m 3 , and accordingly the irradiated area of ​​the low-resistance film layer is transformed into a high-resistance state.

[0016] As a further preference, in step three, a three-dimensional laser scanning system is preferably used to control the focused pulse laser to scan along the trajectory of the memory phase change film layer on a plane or curved surface, directly writing the patch-type resonant unit pattern array composed of the patterned low-resistance phase change film layer array structure, or the slot-type resonant unit pattern array composed of the patterned high-resistance phase change film layer array structure, and obtaining a frequency selective surface.

[0017] As a further preferred embodiment, in step 3, a mask projection processing method may be used to replace the laser scanning direct writing method, wherein:

[0018] A corresponding mask plate is prepared according to the resonant unit pattern array and attached to the surface of the memory phase change film layer. Then, a pulsed laser is used to pass through the transparent area and protective layer of the mask plate to swing and irradiate the corresponding area of ​​the memory phase change film layer, and pattern writing is performed on the patch-type or slot-type FSS resonant unit pattern array composed of low-resistance film layer units or high-resistance film layer units to form a frequency selective surface with a stable resonant frequency and transmission passband.

[0019] As a further preference, for the frequency selective surface prepared as described above, when an error occurs in directly writing the resonant unit pattern array, it is preferred to output a pulsed laser with corresponding phase change parameters through the transmissive protective layer, and utilize the reversible phase change characteristics of the memory phase change film material to erase and modify the directly written resonant unit pattern array, thereby realizing the function of modifying the resonant unit pattern.

[0020] As a further preference, for the frequency selective surface prepared as above, when its surface electromagnetic transmission characteristics need to be changed, it is preferred to output a pulsed laser with corresponding phase change parameters through the transmissive protective layer, and utilize the reversible phase change characteristics of the memory phase change film layer material to partially or completely erase the directly written resonant unit pattern array; then, a pulsed laser with corresponding phase change parameters is used to pass through the transmissive protective layer to directly rewrite the required patterned phase change film layer array structure, thereby realizing the function of changing the surface electromagnetic output characteristics.

[0021] According to another aspect of the present invention, a corresponding frequency selective surface product is also provided.

[0022] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0023] (1) The present invention cleverly utilizes memory phase change materials to achieve reversible phase change characteristics under pulse laser induction conditions. Pulsed lasers with different power densities are used to reversibly induce phase change in the memory phase change film layer deposited on the insulating substrate, thereby achieving erasable and non-volatile functions and strong stability.

[0024] (2) Through the present invention, in the process of writing tens of thousands of resonant unit patterns with pulsed laser, if an error occurs or the dimensional accuracy does not meet the design requirements, the "erasable" function can be used to repair and change it, so that low-cost and waste-free FSS preparation can be achieved; in addition, the "erasable" function can flexibly and variably change the shape, size and arrangement of the phase change resonant unit pattern, thereby realizing the function of changing the resonant frequency and transmission passband of the frequency selective surface. After the processing is completed, the film tissue characteristics and micromorphology can remain stable for a long time, and arbitrary pattern shapes and sizes can be erased and written multiple times, thus having the function of reconstructing the electromagnetic transmission characteristics of the frequency selective surface.

[0025] (3) The present invention also uses thin film deposition technology to coat a memory phase change film layer on any insulating substrate (quartz, sapphire, silicon wafer, ceramic, silicon nitride, epoxy resin, etc.) to form a composite material with a memory phase change film layer; by using a three-dimensional laser scanning system, the preparation of FSS frequency selective surfaces with arbitrary complex curves can also be achieved;

[0026] (4) The present invention does not generate dust, smoke and chemical liquid during the FSS preparation process, does not pollute the optical lens and the working environment, and does not cause any damage to the surface of the insulating substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an overall process flow chart of the laser erasable frequency selective surface preparation method according to the present invention;

[0028] Figure 2 1 is a schematic structural diagram of depositing a memory phase change film layer and a transmissive protective layer on an insulating substrate according to a preferred embodiment of the present invention;

[0029] Figure 3 Schematic diagram of a method for performing a region-selective low-resistance induced phase transition on a high-resistance amorphous memory phase change film layer using a laser three-dimensional scanning device according to a preferred embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of using a laser three-dimensional scanning device to perform a region-selective high-resistance induced phase transition on a low-resistance crystalline memory phase change film layer according to a preferred embodiment of the present invention;

[0031] Figure 5 is a schematic diagram of patterning a memory phase change film using a mask device according to a preferred embodiment of the present invention;

[0032] Figure 6a Schematic diagram of a pulsed laser inducing a memory phase change film through a three-dimensional laser scanning device to change the shape of a patch-type FSS resonant pattern according to a preferred embodiment of the present invention;

[0033] Figure 6b Schematic diagram of a pulsed laser inducing a memory phase change film through a three-dimensional laser scanning device to change the shape of a slot-type FSS resonant pattern according to a preferred embodiment of the present invention;

[0034] Figure 7a Schematic diagram of a preferred embodiment of the present invention, wherein a pulsed laser is passed through a three-dimensional laser scanning device to induce a memory phase change film to change the size of a patch-type FSS resonant pattern;

[0035] Figure 7b Schematic diagram of a pulsed laser inducing a memory phase change film through a three-dimensional laser scanning device to change the size of a slot-type FSS resonant pattern according to a preferred embodiment of the present invention;

[0036] Figure 8 is a schematic diagram of a pulsed laser inducing a memory phase change film through a three-dimensional laser scanning device to change the FSS resonant pattern mode according to a preferred embodiment of the present invention;

[0037] Figure 9 Schematic diagram of a pulsed laser inducing a memory phase change film through a three-dimensional laser scanning device to achieve FSS unit reconstruction according to a preferred embodiment of the present invention;

[0038] Figure 10a Schematic diagram of a pulsed laser through a three-dimensional laser scanning device inducing a memory phase change film to correct an "under-write" condition of an FSS unit according to a preferred embodiment of the present invention;

[0039] Figure 10b Schematic diagram of a pulsed laser through a three-dimensional laser scanning device inducing a correction of an "over-writing" condition of an FSS unit in a memory phase change film according to a preferred embodiment of the present invention;

[0040] Figure 11 This is a schematic diagram of a preferred embodiment of the present invention, in which a pulsed laser is used to induce a memory phase change film through a three-dimensional laser scanning device to achieve FSS preparation of complex surfaces. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0042] Figure 1This is a flow chart of the overall process for fabricating a laser-erasable frequency-selective surface according to the present invention. This invention addresses the shortcomings or defects of the prior art analyzed in the "Background Art" section above by cleverly utilizing the reversible phase transition of memory phase-change materials under pulsed laser induction. By employing pulsed lasers of varying power densities to reversibly induce phase transitions in a memory phase-change film deposited on an insulating substrate, this method achieves high-precision, high-quality fabrication of frequency-selective surfaces and a novel method for reconfiguring their frequency-selective characteristics.

[0043] The following will be combined Figure 1 Let’s explain them one by one in detail.

[0044] Step 1: Using thin film deposition technology, a high-resistance memory phase change film layer 2 and a transmissive protective layer 3 are sequentially deposited on the surface of the insulating substrate 1.

[0045] More specifically, if Figure 2 As shown, the carrier used in the present invention to prepare FSS adopts thin film deposition technology, which may preferably include magnetron sputtering, ion beam sputtering, pulsed laser deposition, chemical vapor deposition or molecular beam epitaxy and other thin film deposition technologies, and a high-resistance state memory phase change film layer 2 is plated on the surface of an insulating substrate 1 (for example, including quartz, sapphire, silicon wafer, ceramic, silicon nitride, epoxy resin, etc.), and a transmissive protective layer 3 can be further plated on the high-resistance state memory phase change film layer 2. The function of the transmissive protective layer 3 is to protect the high-resistance state memory phase change film layer 2 to prevent it from being contaminated by the environment and being volatilized and lost during laser induction.

[0046] Step 2: Using a laser scanning method, a pulsed laser is passed through the transmissive protective layer 3 to selectively irradiate the high-resistance memory phase change film layer 2 in a regional manner, and the temperature of the irradiated area reaches the phase change threshold temperature, thereby forming a patterned low-resistance phase change film layer array structure 11; or the high-resistance memory phase change film layer 2 in the entire area is first converted into a low-resistance film layer, and then a pulsed laser is passed through the transmissive protective layer 3 to selectively irradiate the low-resistance film layer in a regional manner, and the temperature of the irradiated area reaches the melting threshold temperature and is rapidly cooled, thereby forming a patterned high-resistance phase change film layer array structure 12.

[0047] More specifically, see Figure 3 The method for rapidly converting the memory phase change film from a high resistance state to a low resistance state is to use a three-dimensional laser scanning system 6 to output a pulse width of no more than nanoseconds and a pulse laser power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3The pulsed laser 5 in a wide range passes through the transmissive protective layer 3 and selectively irradiates the memory phase change film layer in a regional manner, so that the temperature of the irradiated area reaches the phase change threshold temperature, inducing the high-resistance memory phase change film layer 2 to quickly convert into the low-resistance film layer 4, thereby realizing the preparation of the patterned low-resistance memory phase change film layer array structure 11 and achieving the patch-type FSS function.

[0048] For the preparation of gap-type FSS, see Figure 4 First, the three-dimensional laser scanning system 6 outputs a pulse width no greater than nanoseconds and a power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulse laser 5 converts the high-resistance memory phase change film layer 2 in the entire area into a low-resistance film layer 4, and then uses the three-dimensional laser scanning system 6 to output a pulse width of no more than nanoseconds and a pulse laser power density of 8×10 17 W / m 3 to 10×10 17 W / m 3 The pulsed laser 9 passes through the transmissive protective layer 3 and selectively irradiates the low-resistance film layer 4 in a regional manner, so that the temperature of the irradiated area reaches the melting threshold temperature and is rapidly cooled down, inducing it to quickly convert from a low-resistance state to a high-resistance state film layer 8, thereby realizing the preparation of a high-resistance phase change film layer array structure 12 and achieving the gap-type FSS function.

[0049] Step three, use laser scanning to directly write the patch-type resonant unit pattern array composed of the patterned low-resistance phase change film layer array structure 11, or use laser scanning to directly write the slot-type resonant unit pattern array composed of the patterned high-resistance phase change film layer array structure 12, thereby obtaining a frequency selective surface with a stable resonant frequency and transmission passband.

[0050] According to a preferred embodiment of the present invention, a mask projection method can be used to replace the laser scanning direct writing method to realize the FSS preparation process of the laser induced memory phase change film layer. Figure 5 For the patch-type FSS array, first, a corresponding mask 10 is prepared according to the desired resonant unit pattern array structure, and attached to the surface of the high-resistance memory phase change film layer 2 and the transmissive protective layer 3. Then, the mask is scanned by a three-dimensional laser scanning system 6, and the output pulse width is no more than nanoseconds and the power density is 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulsed laser 5 passes through the light-transmitting area of ​​the mask plate 10 and the transmissive protective layer 3, and performs swing scanning irradiation on the high-resistance memory phase change film layer 2, inducing the film layer to switch from a high-resistance state to a low-resistance state, thereby preparing a patch-type FSS array 13.

[0051] For the slot-type FSS array, it is still necessary to prepare the corresponding mask 10 according to the required pattern. First, the three-dimensional laser scanning system 6 is used to output a pulse width no greater than nanoseconds and a power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulse laser 5 is used to swing and scan the high-resistance memory phase change film layer 2 in the entire area, so that it is completely converted into a low-resistance film layer 4. Then, the laser scanning system 6 outputs a pulse width of no more than nanoseconds and a pulse laser power density of 8×10 17 W / m 3 to 10×10 17 W / m 3 The pulsed laser 9 passes through the light-transmitting area of ​​the mask plate 10 and the transmissive protective layer 3, and swings and irradiates the corresponding area of ​​the low-resistance film layer 4, inducing it to switch from a low-resistance state to a high-resistance state, thereby preparing a slot-type FSS array.

[0052] The method for preparing a frequency selective surface according to the present invention also has the following multiple functions, including pattern modification, array reconstruction, unit correction, etc. Each of these functions will be explained in detail below.

[0053] (1) FSS pattern modification

[0054] (1) Changing the shape of the resonance pattern

[0055] Reference Figure 6a and 6b , the resonant unit pattern shape of the patch type FSS with attached memory phase change film layer is modified. The specific steps are to use a three-dimensional laser scanning system 6 to output a pulse width of no more than nanoseconds and a power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulsed laser 5 is used to irradiate the arc connection position of the resonance unit pattern 14, so that the irradiated area changes from the high-resistance film layer to the low-resistance film layer 4, forming a ring-shaped resonance unit 15. Similarly, a pulse width of no more than nanoseconds and a power density of 8×10 17 W / m 3 to 10×10 17 W / m 3 The pulse laser 9 is reversely modified to change the resonant unit pattern 15 back to the resonant unit pattern 14. The resonant unit pattern of the gap-type FSS with a memory phase change film layer is modified. The specific steps are to use a three-dimensional laser scanning system 6 to output a pulse width of no more than nanoseconds and a power density of 8×10 17 W / m 3to 10×10 17 W / m 3 The pulsed laser 9 within the range irradiates the arc connection position of the resonance unit pattern 16, so that the irradiated area changes from the low-resistance film layer 4 to the high-resistance film layer 8, forming a ring-shaped resonance unit 17. Similarly, a pulse width of no more than nanoseconds and a power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulse laser 5 is used to perform reverse modification, changing the resonance unit pattern 17 back to the resonance unit pattern 16.

[0056] (2) Changing the resonant pattern size

[0057] Reference Figure 7a and 7b , the resonant unit pattern size of the patch type FSS with attached memory phase change film layer is modified. The specific steps are to use a three-dimensional laser scanning system 6 to output a pulse width no greater than nanoseconds and a power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulsed laser 5 irradiates the edge of the narrow ring resonant unit pattern 18, so that the irradiated area changes from the high-resistance film layer 2 to the low-resistance film layer 4, forming a wide ring resonant unit pattern 19. Similarly, a pulse width of no more than nanoseconds and a power density of 8×10 17 W / m 3 to 10×10 17 W / m 3 The pulse laser 9 is reversely modified to change the resonant unit pattern 19 back to the resonant unit pattern 18. The size of the resonant unit pattern of the gap-type FSS with attached memory phase change film is modified. The specific steps are to use the three-dimensional laser scanning system 6 to output a pulse width of no more than nanoseconds and a power density of 8×10 17 W / m 3 to 10×10 17 W / m 3 The pulsed laser 9 within the range irradiates the edge of the narrow ring resonant unit pattern 20, so that the irradiated area changes from the low-resistance film layer 4 to the high-resistance film layer 8, forming a wide ring resonant unit pattern 21. Similarly, a pulse width of no more than nanoseconds and a power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulse laser 5 is used to perform reverse modification, and the resonance unit pattern 21 is changed back to the resonance unit pattern 20.

[0058] (3) Change the resonance pattern mode

[0059] Reference Figure 8 , the resonant unit pattern mode of the patch type FSS with attached memory phase change film is modified. The specific steps are to use the laser scanning system 6 to output a pulse width of no more than nanoseconds and a pulse laser power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulsed laser 5 within the range irradiates the border connection of the square ring resonant pattern 22, and the irradiated area changes from the high-resistance film layer 2 to the low-resistance film layer 4, forming a grid-type resonant unit pattern 23. At this time, the filtering performance of the FSS array changes, achieving functional conversion. The above operation can be achieved by pulse width no greater than nanoseconds and pulse laser power density output at 8×10 17 W / m 3 to 10×10 17 W / m 3 The pulse laser 9 within the range performs a reverse operation to change the mesh resonant unit pattern mode 23 back to the square ring resonant unit pattern mode 22.

[0060] (2) Other functions

[0061] (1) FSS array reconstruction

[0062] Reference Figure 9 The specific steps are to first use a three-dimensional laser scanning system 6 to output a pulse width of no more than nanoseconds and a power density of 8×10 17 W / m 3 to 10×10 17 W / m 3 The pulse laser 9 within the range irradiates the original resonant unit pattern 24, so that the irradiated area changes from the low-resistance film layer 4 to the high-resistance film layer 8, and the entire film layer is restored to the high-resistance film layer 2, realizing the erasing function; then the laser scanning system 6 is used to output a pulse width of no more than nanoseconds and a pulse laser power density of 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulsed laser 5 within the range is used to reconstruct the low-resistance array unit, reconstructing the resonant unit into a square ring 25, and obtaining an FSS array with different resonant frequencies and transmission passbands, thus realizing the FSS reconstruction function. Similarly, the laser reverse phase change process can also be used to reconstruct the gap-type FSS unit with a memory phase change film layer.

[0063] (2) FSS unit correction

[0064] Reference Figure 10a and 10b , is the implementation process of the correction of the patch type FSS resonant unit with the memory phase change film layer. When the patch type FSS resonant unit pattern is wrong during the preparation process, different processing solutions should be implemented according to the error type. When "writing is insufficient", refer to Figure 10a The laser scanning system 6 is used to output pulse width no more than nanoseconds and the pulse laser power density is 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulse laser 5 within the range is used to supplement the remaining area so that the error resonance unit pattern 26 is corrected to the normal resonance unit pattern 27; when "overwriting", refer to Figure 10b The laser scanning system 6 is used to output pulse width no more than nanoseconds and the pulse laser power density is 8×10 17 W / m 3 to 10×10 17 W / m 3 Pulsed laser light 9 within the range of the laser diode is used to irradiate and erase the excess area, correcting the faulty resonant unit pattern 28 to a normal resonant unit pattern 29. Similarly, a laser reverse phase change process can be used to correct the gap-type FSS resonant unit with a memory phase change film layer. This method allows for repeated erasure and rewriting, significantly improving the fabrication accuracy and fault tolerance of the FSS array.

[0065] See Figure 11 The above embodiment can use a three-dimensional laser scanning device to selectively induce the memory phase change film layer deposited on the curved substrate to achieve laser erasing preparation of the curved FSS.

[0066] According to another preferred embodiment of the present invention, in step 1, the high-resistance memory phase change film layer is preferably a pseudo-binary alloy material composed of germanium telluride (GeTe) and antimony telluride (Sb2Te3), and can be selected from any one or a combination of the following substances: GeTe, Ge2Sb2Te5, Ge1Sb2Te4, Ge1Sb4Te7. This type of material has two structural forms, crystalline and amorphous, and can achieve rapid state switching under external stimulation, accompanied by changes in a series of physical properties such as refractive index and conductivity. Among them, GeTe is the material with the most significant change in conductivity before and after state switching among this type of materials, and has broad development prospects in the design and preparation of frequency selective surfaces.

[0067] Specifically, GeTe has two relatively stable crystalline phases: amorphous a-GeTe and crystalline c-GeTe (including rhombohedral and cubic phases). Under appropriate external temperature stimulation, it can rapidly transform between the amorphous and crystalline states. Due to the significant electrical differences between amorphous a-GeTe and crystalline c-GeTe—the square resistance of amorphous a-GeTe films is approximately 106Ω, while that of crystalline c-GeTe is approximately 10Ω, with a variation of 4-5 orders of magnitude—then it can achieve high-resistance and low-resistance state conversion. When the external temperature is above 175°C but below the melting point of 720°C, the amorphous a-GeTe film begins to transform into a crystalline c-GeTe film. Only when the external temperature reaches above the melting point of 720°C and is rapidly cooled will the crystalline c-GeTe film transform into amorphous a-GeTe.

[0068] In addition, the deposited memory phase change material can preferably be doped to meet the actual use requirements of different applications. The doping elements include silver, nitrogen, etc. The substrates that can be used include quartz, sapphire, silicon wafers, ceramics, silicon nitride, epoxy resin and other materials suitable for the deposition of memory phase change films. The optional methods for preparing the carrier include thin film deposition technologies such as magnetron sputtering, ion beam sputtering, pulsed laser deposition, chemical vapor deposition or molecular beam epitaxy, as well as thin film attachment technology using flexible substrate transfer, to deposit the memory phase change material or memory phase change doping material on the surface of the substrate to form a carrier for preparing FSS.

[0069] More specifically, in the process of inducing the low-resistance state of the memory phase change film layer using a pulsed laser, the pulsed laser power, repetition frequency, pulse width, scanning speed and repetition times are combined to selectively scan the film area. It is necessary to ensure that the power density of the pulsed laser is between the low-resistance phase change threshold and the melting threshold of the memory phase change film layer. After optimization, the power density is preferably 1×10 17 W / m 3 to 7.5×10 17 W / m 3 Laser pulses can transform a high-resistance film layer into a low-resistance film layer with higher purity. Alternatively, when using a pulsed laser to induce a high-resistance state in a memory phase change film layer, the pulsed laser power, repetition frequency, pulse width, scanning speed, and repetition times are combined to selectively scan the film area. It is necessary to ensure that the power density of the pulsed laser is between the melting threshold and the vaporization threshold of the memory phase change film layer and that it can be cooled instantly. After optimization, a power density of 8×10 17 W / m 3 to 10×10 17 W / m 3 Laser pulses can convert the low-resistance film layer into a high-resistance film layer with higher purity.

[0070] According to another preferred embodiment of the present invention, in step 2, the pulse laser preferably has the following low-resistance phase transition parameters: pulse width is no more than nanoseconds, power density is 1×10 17 W / m 3 to 7.5×10 17 W / m 3 , and accordingly convert the irradiated area of ​​the high-resistance memory phase change film layer into a low-resistance state; or the pulse laser preferably has the following high-resistance phase change parameters: pulse width is no more than nanoseconds, power density is 8×10 17 W / m 3 to 10×10 17 W / m 3 , and accordingly the irradiated area of ​​the low-resistance film layer is transformed into a high-resistance state.

[0071] According to another preferred embodiment of the present invention, in step three, a three-dimensional laser scanning system is preferably used to control the focused pulse laser to scan along the trajectory of the memory phase change film layer on a plane or curved surface, directly writing the patch-type resonant unit pattern array composed of the patterned low-resistance phase change film layer array structure, or the slot-type resonant unit pattern array composed of the patterned high-resistance phase change film layer array structure, and obtaining a frequency selective surface.

[0072] Furthermore, laser writing system equipment may include, for example, a pulsed laser light source, a beam shaping system, a dynamic focusing system, a 3D scanning system, a scanning focusing device, and a high-precision displacement device. The laser light source can utilize a laser with a central wavelength of 300nm to 1200nm and a pulse width of nanoseconds to femtoseconds. Different writing process parameters are selected based on the type of pulsed laser light source. The beam shaping system can shape the light spot to various shapes, such as circular, square, or linear. The 3D scanning system can be composed of different scanning devices based on different scanning methods. For example, laser-induced processing can be performed using 3D galvanometer scanning, rotating mirror scanning, or focusing mirror-translation stage linkage processing.

[0073] According to another preferred embodiment of the present invention, in step three, a mask projection processing method can preferably be used to replace the laser scanning direct writing, wherein a corresponding mask plate is prepared according to the resonance unit pattern array and attached to the surface of the memory phase change film layer, and then a pulsed laser is used to pass through the light-transmitting area and the protective layer of the mask plate to swing and irradiate the corresponding area of ​​the memory phase change film layer, and patterned writing is performed on the patch type resonance unit pattern array composed of the patterned low-resistance phase change film layer array structure or the slot type resonance unit pattern array composed of the patterned high-resistance phase change film layer array structure to form a frequency selective surface with a stable resonance frequency and a transmission passband.

[0074] More specifically, the laser projection device consists of a laser light source, a beam shaping system, a three-dimensional deflection scanning system, a focusing system, and a mask system. The mask system primarily includes an FSS pattern mask plate, which is designed and manufactured with aberration correction and covers the memory phase change film layer. This effectively avoids distortion during beam projection, thereby ensuring the dimensional and shape accuracy of the FSS array produced by laser patterning. The laser light source outputs a pulsed laser with a pulse width no greater than nanoseconds. The focusing system obtains the required pulsed laser power density, and the mask system is deflected and scanned by the three-dimensional deflection scanning system. The focused laser beam is then used to directly pattern the memory film layer through the FSS mask plate, inducing phase change, thereby achieving rapid preparation of the FSS resonant pattern.

[0075] In combination with the above description, the basic principle of the method of the present invention is to deposit a high-resistance memory phase change film layer instead of a metal film layer on the surface of a flat or curved insulating substrate, use a pulse laser with a pulse width of no more than nanoseconds, output a suitable pulse laser power density, and irradiate the memory phase change film layer to make the film layer temperature reach the phase change threshold temperature, inducing it to quickly convert from a high-resistance state to a low-resistance state, and use a three-dimensional laser scanning system to control the scanning trajectory of the focused pulse laser beam, directly write a resonant unit graphic structure array, and realize the preparation function of a flat or complex curved frequency selective surface. Once the pulse laser makes an error or a large error in the process of writing the resonant unit graphic structure array, a pulse laser with a pulse width of no more than nanoseconds can be used to output a suitable power density to irradiate the resonant unit graphic structure array with the error or large error, so that the temperature of the phase change film layer reaches the melting threshold temperature and quickly cools down, inducing the memory phase change film layer to reverse phase change, and quickly recovering from the low resistance state to the original high resistance state, thereby achieving the purpose of erasing the resonant unit graphic structure array with the error or large error; then a pulse laser with a pulse width of no more than nanoseconds is used to output a power density that makes the film layer temperature reach the phase change threshold temperature, and rewrite the resonant unit graphic structure array that meets the graphic size accuracy requirements, thereby realizing a repeatable modification function. When it is necessary to reconstruct the resonant frequency point and transmission passband of the frequency selective surface, several reconstruction modes can be used:

[0076] Reconstruction mode ①: A three-dimensional laser scanning system is used to control a focused pulsed laser with a pulse width no greater than nanoseconds. The output is a pulsed laser power density that can make the phase change film layer reach the phase change threshold temperature, or a power density that can make the phase change film layer reach the melting threshold temperature and quickly cool it. This selectively induces a positive or reverse phase change in a part of the memory phase change film layer, writes or erases part of the structure of the resonant unit pattern, and modifies the resonant unit pattern.

[0077] Reconstruction mode ②: A three-dimensional laser scanning system is used to control a focused pulsed laser with a pulse width no greater than nanoseconds. The output pulsed laser power density can make the phase change film layer reach the phase change threshold temperature, thereby increasing the size of the resonant unit pattern; or the output power density can make the phase change film layer reach the melting threshold temperature and rapidly cool it, thereby reducing the size of the resonant unit pattern.

[0078] Reconstruction mode ③: A three-dimensional laser scanning system is used to control a pulsed laser of no more than nanoseconds, and the output can make the phase change film layer reach the melting threshold temperature and quickly cool it, inducing the memory phase change film layer to reverse phase change, restoring the original high-resistance state, and erasing the entire written resonant unit graphic structure array; then a pulsed laser with a pulse width of no more than nanoseconds is used to output a pulsed laser power density that can make the phase change film layer reach the phase change threshold temperature, inducing the memory phase change film layer to quickly switch from a high-resistance state to a low-resistance state, and the pulsed laser scanning trajectory is controlled by the three-dimensional laser scanning system to rewrite another resonant unit graphic structure array, thereby realizing the resonant working point preparation function of the FSS frequency selective surface that reconstructs the complex surface.

[0079] Reconstruction mode ④: Using a pulsed laser with a pulse width no greater than nanoseconds, the output can make the phase change film layer reach the phase change threshold temperature. This induces the memory phase change film layer in the area surrounding the patch-type conductive pattern to quickly switch from a high-resistance state to a low-resistance state, constructing a grid array structure with a different filtering function from the patch-type FSS, and realizing the electromagnetic transmission characteristic conversion function.

[0080] The above reconstruction mode uses a patch-type frequency selective surface resonator as an example. The write operation corresponds to the forward low-resistance phase transition of the memory phase change film, and the erase operation corresponds to the reverse high-resistance phase transition. The corresponding mode also applies to slot-type frequency selective surface resonators. In this case, the write operation corresponds to the reverse high-resistance phase transition of the memory phase change film, and the erase operation corresponds to the forward low-resistance phase transition.

[0081] Several specific embodiments are given below to facilitate understanding of the present invention.

[0082] Example 1: Nanosecond laser induced germanium telluride thin film to achieve phase change function.

[0083] (1) The surface of the sapphire substrate was ultrasonically cleaned with detergent, acetone, and deionized water for 40 minutes each, and then dried with nitrogen.

[0084] (2) The sapphire substrate was subjected to radio frequency sputtering deposition in a magnetron sputtering apparatus. The sputtering target used was a high-purity germanium telluride target. The sputtering power was 30 W, the sputtering time was 20 min, the sputtering pressure was 0.5 Pa, and the obtained film thickness was 300 nm.

[0085] (3) A three-dimensional galvanometer laser scanning system was used to scan and induce the amorphous germanium telluride film. The light source used was an infrared nanosecond laser with a wavelength of 1064 nm. The laser repetition frequency was adjusted to 1.7 kHz, the pulse width was 40 ns, and the power density was 1.5×10 17 W / m 3 The scanning spot was elliptical, the scanning speed was 17 mm / s, the filling method was orthogonal lines, the line spacing was 0.01 mm, and the number of scans was 1. XRD tests were performed on the samples before and after the laser exposure, and it was found that the pulsed laser under this set of parameters can effectively induce the phase transformation of high-resistance amorphous germanium telluride thin films into low-resistance crystalline films.

[0086] (4) A three-dimensional galvanometer laser scanning system was used to scan and induce the low-resistance crystalline germanium telluride film. The light source used an infrared nanosecond laser with a wavelength of 1064 nm. The laser repetition frequency was adjusted to 200 kHz, the pulse width was 5 ns, and the power density was 8.5×10 17 W / m 3 The scanning spot was elliptical, the scanning speed was 170 mm / s, the filling method was orthogonal lines, the line spacing was 0.01 mm, and the number of scans was 1. XRD analysis of the sample after laser exposure showed no characteristic peaks, indicating that the laser under these parameters can effectively induce the phase transition of low-resistance crystalline germanium telluride thin films into high-resistance amorphous films.

[0087] Example 2: A frequency selective surface loaded with a germanium telluride thin film pattern realizes the function of changing the resonant frequency before and after laser erasure.

[0088] A quartz glass with a size of 200mm×200mm and a thickness of 2mm was selected as the substrate. Its dielectric constant is 3.75 and the loss tangent is 0.0004. A germanium telluride film with a thickness of 300nm was deposited on the quartz surface by magnetron sputtering technology. Subsequently, a dual-galvanometer laser scanning system was used to scan and induce the amorphous germanium telluride film. The light source used was an infrared nanosecond fiber laser with a wavelength of 1064nm. The crystallization processing parameters in Example 1 can be used to transform the high-resistance amorphous film into a low-resistance crystalline state. The processed area is a circular ring with a period of 10mm, an inner radius of 3.4mm, and an outer radius of 3.6mm. The conductivity of the treated area is significantly improved due to crystallization, forming a resonant pattern. Under vertical incidence conditions, S 21The frequency response curve includes a TE polarized wave resonant frequency of 9.092 GHz and a -3dB bandwidth of 5.65 GHz; a TM polarized wave resonant frequency of 8.531 GHz and a -3dB bandwidth of 5.60 GHz; the amorphous parameters in Example 1 are used to process the crystalline region of the film to transform the film from a crystalline state to an amorphous state, and then the crystallization parameters are used to induce a new crystallization pattern. The new pattern is a ring with a period of 10 mm, an inner radius of 2.4 mm, an outer radius of 2.6 mm, and an S under vertical incidence conditions. 21 The frequency response curves show a TE polarized wave resonant frequency of 12.700 GHz and a -3dB bandwidth of 4.21 GHz; a TM polarized wave resonant frequency of 12.625 GHz and a -3dB bandwidth of 4.19 GHz. This demonstrates that the planar frequency selective surface loaded with germanium telluride film can achieve the function of changing the resonant frequency before and after laser induction.

[0089] In summary, the present invention enables the fabrication, modification, and reconstruction of frequency selective surfaces in an efficient, controllable, and reliable manner. Furthermore, the resulting product exhibits non-volatility and strong stability, allowing for repeated modification of the resonant unit pattern size and array, ensuring the accuracy and quality of the fabrication of frequency selective surfaces for complex curved surfaces. Furthermore, the resonant frequency and transmission passband of the frequency selective surface can be varied over a wide range. This method also offers the advantages of being pollution-free and harmless to the insulating substrate surface, thus possessing broad application prospects.

[0090] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a laser-erasable frequency selective surface, characterized in that: The method comprises the following steps: Step 1: Using thin film deposition technology, a high-resistance memory phase change film layer (2) and a transmissive protective layer (3) are sequentially deposited on the surface of an insulating substrate (1); wherein the high-resistance memory phase change film layer (2) is a pseudo-binary alloy material composed of germanium telluride and antimony telluride, and is doped with elements including silver and nitrogen; the material has two structural forms, crystalline and amorphous, and realizes rapid state switching under the excitation of a pulsed laser, accompanied by changes in physical properties such as refractive index and conductivity; Step 2: The output pulse width is no more than nanoseconds, and the power density is set to 1×10 17 W / m 3 to 7.5×10 17 W / m 3 A pulsed laser is applied to the high-resistance memory phase change film layer (2) so as to transmit the pulsed laser through the transmissive protective layer (3) to selectively irradiate the high-resistance memory phase change film layer (2), and the temperature of the irradiated region reaches the phase change threshold temperature, thereby forming a patch-type resonant unit pattern array consisting of a patterned low-resistance phase change film layer array structure (11); or First, the output pulse width is no more than nanoseconds, and the power density is set to 1×10 17 W / m 3 to 7.5×10 17 W / m 3 The pulse laser converts the high-resistance memory phase change film layer (2) in the entire region into a low-resistance film layer, and then outputs a pulse width of no more than nanoseconds and a power density of 8×10 17 W / m 3 to 10×10 17 W / m 3 A pulsed laser is applied to the low-resistance film layer through the transmissive protective layer (3) to selectively irradiate the low-resistance film layer, and the temperature of the irradiated region reaches the melting threshold temperature and is rapidly cooled, thereby forming a slot-type resonant unit pattern array composed of a patterned high-resistance phase change film layer array structure (12); Step 3: A mask projection processing method and a laser projection device are used to form a frequency selective surface, wherein a corresponding mask plate (10) is prepared according to the resonance unit pattern array structure, and attached to the surface of the high-resistance memory phase change film layer (2) and the transmissive protective layer (3), and then a pulsed laser is used to pass through the light-transmitting area of ​​the mask plate (10) and the transmissive protective layer (3) to swing and irradiate the corresponding area of ​​the high-resistance memory phase change film layer (2), and pattern-write a patch-type resonance unit pattern array composed of the patterned low-resistance phase change film layer array structure (11) or a slot-type resonance unit pattern array composed of the patterned high-resistance phase change film layer array structure (12), and form a frequency selective surface with a stable resonance frequency point and a transmission passband; The laser projection device is composed of a laser light source, a beam shaping system, a three-dimensional deflection scanning system, a focusing system and a mask system, wherein the mask system includes a frequency selective surface pattern mask plate covered on the high-resistance memory phase change film layer (2); the laser light source outputs a pulse laser with a central wavelength of 300nm to 1200nm and a pulse width of no more than nanoseconds, and the required pulse laser power density is obtained through the focusing system. The mask system is deflected and scanned by the three-dimensional deflection scanning system, and the focused laser beam is directly patterned through the frequency selective surface pattern mask plate to induce the phase change of the memory film layer, thereby realizing the rapid preparation of the frequency selective surface resonance pattern; The frequency selective surface prepared above has the following multiple working modes: First reconstruction mode: using a focused pulse laser with a pulse width no greater than nanoseconds, outputting a pulse laser power density that can cause the phase change film layer to reach the phase change threshold temperature, or outputting a power density that causes the phase change film layer to reach the melting threshold temperature and rapidly cool it, selectively inducing a forward or reverse phase change in a portion of the memory phase change film layer, writing or erasing a portion of the structure of the resonant unit pattern, and modifying the resonant unit pattern; Second reconstruction mode: Using a focused pulse laser with a pulse width no greater than nanoseconds, the output pulse laser power density can make the phase change film layer reach the phase change threshold temperature, thereby increasing the size of the resonant unit pattern; or output power density that makes the phase change film layer reach the melting threshold temperature and rapidly cool it, thereby reducing the size of the resonant unit pattern; The third reconstruction mode: using a pulsed laser with a pulse width of no more than nanoseconds, outputting a power density that can make the phase change film layer reach the melting threshold temperature and rapidly cool it, inducing the reverse phase change of the memory phase change film layer, restoring the original high-resistance state, and erasing the entire resonant unit graphic structure array that has been written; then using a pulsed laser with a pulse width of no more than nanoseconds, outputting a pulsed laser power density that can make the phase change film layer reach the phase change threshold temperature, inducing the memory phase change film layer to rapidly switch from a high-resistance state to a low-resistance state, controlling the pulsed laser scanning trajectory, and rewriting another resonant unit graphic structure array, thereby realizing the resonant working point preparation function of reconstructing the complex curved surface frequency selective surface; The fourth reconstruction mode: using a pulsed laser with a pulse width no greater than nanoseconds, the output can make the phase change film layer reach the phase change threshold temperature, inducing the memory phase change film layer in the area around the patch-type conductive pattern to quickly switch from a high-resistance state to a low-resistance state, constructing a grid array structure with a different function from the patch-type frequency selective surface filtering, and realizing the electromagnetic transmission characteristic conversion function.

2. The preparation method according to claim 1, wherein In step 1, the high-resistance memory phase change film layer (2) is selected from any one of the following materials or a combination thereof: Ge2Sb2Te5, Ge1Sb2Te4, Ge1Sb4Te7.

3. The preparation method according to claim 1 or 2, wherein In step 1, the transmissive protective layer (3) is a passive material having a transmissive wavelength in the range of 300 nm to 1200 nm.

4. A frequency selective surface product, characterized in that: It is prepared by the method according to any one of claims 1 to 3.

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