Photonic crystal film, preparation method thereof and device

Abstract

The invention provides a photonic crystal film, a preparation method thereof and a device. A mask layer is grown on the surface of a film of a substrate to serve as an etching mask plate, the photonic crystal film is prepared, and the mask layer is still reserved after etching is finished. According to the method, the damage of a wet etching solution to a photonic crystal film in a conventional process is effectively avoided, and meanwhile, on the basis of not changing the shape of an optical energy band of the photonic crystal, the position of the energy band of the photonic crystal is accurately regulated and controlled by adjusting the thickness of SiO2. Wherein the mask layer is always reserved in the whole technological process and serves as a protective layer to serve as a mask plate, and the integrity of the periodic structure of the one-dimensional / two-dimensional photonic crystal film is ensured. On the basis, through not removing the SiO2 mask layer and adjusting the thickness of the mask layer, dual functions of structure protection and optical adjustment on the one-dimensional / two-dimensional photonic crystal film are realized, so that the device performance is enhanced and the application range is expanded.

Description

Technical Field

[0001] The present invention belongs to the field of photonic crystals, and in particular relates to a photonic crystal film, a preparation method thereof, and a device. Background Art

[0002] In traditional GaAs-based one-dimensional / two-dimensional photonic crystal thin film fabrication processes, photoresist is often used as an exposure mask. However, photoresist's low strength makes it inadequate for high-precision processing. Prior art often uses silicon dioxide as an exposure mask, which is then removed via wet etching. Wet etching is a processing method used in micromechanical structure fabrication that involves etching the material in a liquid chemical solution. While it offers advantages such as fast etching rates and low cost, it also presents disadvantages such as difficulty controlling etching thickness.

[0003] In the preparation of gallium arsenide-based one-dimensional / two-dimensional photonic crystal films, a wet etching solution containing fluoric acid (BOE solution) is usually required to remove silicon dioxide. The "BOE solution" refers to a buffered oxide etching solution composed of a mixture of a 49% hydrofluoric acid aqueous solution and an ammonium fluoride aqueous solution in a certain proportion. This wet etching process is difficult to ensure that the etching level is just enough to completely etch the silicon dioxide on the GaAs surface, and it is accompanied by the risk of damaging the surface of the GaAs photonic crystal and causing the grating structure to collapse. However, during the preparation process using the above-mentioned traditional method, the fluorescence intensity of the material after wet etching is several times lower than that of the material before wet etching. This type of wet etching solution will damage the GaAs film, not only destroying the flatness of the GaAs photonic crystal surface, but also reducing its luminescence performance. Therefore, how to protect the structural integrity and luminescence performance of GaAs photonic crystals in the processing technology has become a difficult problem. Summary of the Invention

[0004] Therefore, the purpose of the present invention is to overcome the shortcomings of the prior art and provide a photonic crystal film, a preparation method, and a device thereof. Compared with the traditional preparation process, after using a silicon dioxide layer as a mask to etch a GaAs film to form a GaAs photonic crystal structure, by retaining the surface silicon dioxide mask, the GaAs surface is prevented from contacting the acidic etching solution, solving the problem of fluorescence intensity degradation caused by corrosion of the GaAs surface. At the same time, the thickness of the SiO2 mask layer is used to regulate the energy band position of the one-dimensional / two-dimensional photonic crystal film, achieving the dual functions of structural protection and optical regulation.

[0005] Before describing the present invention, the terms used in this article are defined as follows:

[0006] The term "ICPPECVD" means: Inductively Coupled Plasma Enhanced Chemical Vapor Deposition.

[0007] The term "ICP" refers to: Inductively Coupled Plasma Etching.

[0008] The term "photonic crystal" refers to an artificial periodic dielectric structure with photonic bandgap properties.

[0009] To achieve the above-mentioned object, the first aspect of the present invention provides a photonic crystal film, which comprises, from bottom to top, a substrate and a mask layer deposited on the surface of the substrate; wherein:

[0010] The mask layer is etched on the substrate to form a photonic crystal periodic structure pattern;

[0011] The photonic crystal film further includes air cavity regions spaced apart in the photonic crystal periodic structure pattern;

[0012] Preferably, the structure of the photonic crystal periodic structure pattern is a one-dimensional photonic crystal periodic structure pattern and / or a two-dimensional photonic crystal periodic structure pattern.

[0013] According to the photonic crystal film of the first aspect of the present invention,

[0014] The material of the substrate is selected from one or more of the following: gallium arsenide, indium phosphide, InGaP, AlGaAs, silicon, gallium nitride, glass / fused silica, preferably selected from one or more of the following: gallium arsenide, InGaP, AlGaAs, indium phosphide, more preferably gallium arsenide and / or InGaP; and / or

[0015] The thickness of the substrate is 100-500 nm, preferably 150-400 nm, and more preferably 150-200 nm.

[0016] According to the photonic crystal film of the first aspect of the present invention,

[0017] The material of the mask layer is selected from one or more of the following: silicon dioxide, aluminum oxide, silicon nitride, hafnium oxide, chromium metal film, nickel metal film, preferably selected from one or more of the following: silicon dioxide, aluminum oxide, silicon nitride, most preferably silicon dioxide;

[0018] The thickness of the mask layer is 500 nm or less, preferably 300 nm or less, more preferably 100 nm or less; and / or

[0019] The thickness of the mask layer can be adjusted, and as the thickness of the mask layer is adjusted, the energy band wavelength of the photonic crystal film shifts accordingly;

[0020] Preferably, the range of the corresponding shift of the energy band wavelength is 10 to 80 nm, more preferably 10 to 50 nm, further preferably 10 to 30 nm, and further preferably 10 to 29 nm.

[0021] According to the photonic crystal film of the first aspect of the present invention,

[0022] The period of the photonic crystal is 250 to 600 nm, preferably 300 to 500 nm, more preferably 350 to 450 nm; and / or

[0023] The cross-sectional shape of the air chamber area is selected from one or more of the following: square, circle, triangle, ellipse, hexagon, preferably selected from one or more of the following: square, circle, triangle, most preferably square;

[0024] Preferably, the cross-sectional area of ​​the air chamber region is 8000 nm 2 ~160000nm 2 , more preferably 9000nm 2 ~122500nm 2 , more preferably 10000nm 2 ~22500nm 2 ;

[0025] More preferably, when the cross-sectional shape of the air cavity region is a square, the side length of the cross-sectional shape of the air cavity region is 90 to 400 nm, more preferably 95 to 350 nm, and further preferably 100 to 150 nm.

[0026] A second aspect of the present invention provides a method for preparing the photonic crystal film according to the first aspect, the method comprising the following steps in sequence:

[0027] 1) growing the mask layer on the substrate;

[0028] 2) spin-coating a photoresist on the mask layer and performing photolithography to form a photoresist pattern having a photonic crystal periodic structure pattern, and etching the photonic crystal periodic structure pattern;

[0029] 3) removing the photoresist on the mask layer; and

[0030] 4) Using the mask layer as a mask plate, etching a pattern having a photonic crystal periodic structure on the substrate, and retaining the mask layer.

[0031] According to the method of the second aspect of the present invention, in said step 1):

[0032] The method of growing the mask layer is selected from one or more of the following: inductively coupled plasma enhanced chemical vapor deposition, electron beam evaporation, sputtering deposition, atomic layer deposition, thermal oxidation, and wet chemical deposition, preferably selected from one or more of the following: inductively coupled plasma enhanced chemical vapor deposition, electron beam evaporation, sputtering deposition, and atomic layer deposition, and most preferably inductively coupled plasma enhanced chemical vapor deposition; and / or

[0033] The time for growing the mask layer is 3 minutes to 30 minutes, preferably 4 minutes to 20 minutes, and more preferably 5 minutes to 7 minutes.

[0034] According to the method of the second aspect of the present invention, in said step 2):

[0035] The etching method of the photonic crystal periodic structure pattern is selected from one or more of the following: inductively coupled plasma etching, reactive ion etching, wet etching, focused ion beam etching, laser induced etching, preferably selected from one or more of the following: inductively coupled plasma etching, reactive ion etching, focused ion beam etching, most preferably inductively coupled plasma etching; and / or

[0036] The etching time of the photonic crystal periodic structure pattern is 5 minutes to 30 minutes, preferably 6 minutes to 20 minutes, and more preferably 7 minutes to 15 minutes.

[0037] According to the method of the second aspect of the present invention, in said step 4):

[0038] The etching method on the substrate is selected from one or more of the following: inductively coupled plasma etching, reactive ion etching, wet etching, focused ion beam etching, laser induced etching, preferably selected from one or more of the following: inductively coupled plasma etching, reactive ion etching, focused ion beam etching, most preferably inductively coupled plasma etching; and / or

[0039] The etching time on the substrate is 40s to 140s, preferably 42s to 120s, and more preferably 45s to 60s.

[0040] According to the method of the second aspect of the present invention, the step 2) further comprises the following steps:

[0041] In a photoresist pattern having a photonic crystal periodic structure pattern, regions uncovered by the photoresist are etched to form air cavities in the periodic photonic crystal structure.

[0042] A third aspect of the present invention provides a device for optical communication or optoelectronics, the device comprising the photonic crystal film according to the first aspect;

[0043] Preferably, the device for optical communication is selected from one or more of the following: photonic crystal laser, photonic crystal waveguide, photonic crystal resonant cavity, photonic crystal filter, slow light device; and / or

[0044] Preferably, the device for optoelectronics is selected from one or more of the following: a light detector, a light modulator, a photonic crystal solar cell, a quantum light source, and a surface plasmon photonic crystal.

[0045] According to a preferred embodiment of the present invention, the method for preparing a gallium arsenide-based one-dimensional / two-dimensional photonic crystal film of the present invention comprises the following steps:

[0046] (1) Deposition of silicon dioxide layer: Deposition and growth of silicon dioxide layer on the surface of GaAs substrate;

[0047] (2) Photolithography of the silicon dioxide layer: applying photoresist on the silicon dioxide mask layer and performing photolithography to form a photoresist pattern with a periodic pattern;

[0048] (3) Etching of the silicon dioxide layer: using etching technology to transfer the periodic pattern of the photonic crystal to the silicon dioxide mask layer, followed by debonding;

[0049] (4) Etching of GaAs-based substrate: Using the silicon dioxide layer with a surface pattern as a mask, a photonic crystal pattern is etched on the GaAs-based material;

[0050] (5) Retention of the silicon dioxide layer: After step (4), the entire preparation process is completed, and the silicon dioxide layer does not need to be removed by wet etching, but is completely retained as a mask layer.

[0051] The substrate is gallium arsenide and the mask layer is silicon dioxide.

[0052] The silicon dioxide layer is deposited by inductively coupled plasma enhanced chemical vapor deposition (ICPPECVD) technology.

[0053] The photoresist pattern with a periodic structural pattern is a geometric structure with one-dimensional or two-dimensional periodicity.

[0054] The silicon dioxide layer and the GaAs film are etched by using an inductively coupled plasma (ICP) etching technique.

[0055] The silicon dioxide layer is retained throughout the entire process and is not removed by any method.

[0056] According to another preferred embodiment of the present invention, the method for preparing a GaAs photonic crystal thin film of the present invention comprises the following steps:

[0057] (1) Deposition of silicon dioxide layer: Deposit and grow silicon dioxide layer on the surface of GaAs film;

[0058] (2) Photolithography of the silicon dioxide layer: applying a resist on the silicon dioxide mask layer and performing photolithography to form a photoresist pattern with a periodic pattern;

[0059] (3) Etching of the silicon dioxide layer: The photonic crystal pattern is transferred to the silicon dioxide mask layer using etching technology, followed by debonding.

[0060] (4) GaAs etching: using silicon dioxide as a mask to etch a photonic crystal pattern on the GaAs film;

[0061] (5) Retention of the silicon dioxide layer: During the entire process, the silicon dioxide layer is not removed, but is completely retained as a mask layer and does not affect the optical energy band of the final GaAs photonic crystal film.

[0062] The optical energy band is one of the most important performance indicators of photonic crystals, closely related to the geometric dimensions of its periodic structure and the refractive index of the material. In the present invention, the presence of SiO2 affects the position of the photonic crystal's energy band, but has no effect on its band shape or microcavity quality factor. Therefore, the present invention adjusts the position of the photonic crystal's energy band by adjusting the thickness of the SiO2 mask layer, achieving both structural protection and optical adjustment, thereby improving device performance and its application range.

[0063] In the preparation of GaAs photonic crystal films, the etching solution in the step of removing the silicon dioxide mask by wet etching damages the surface of the GaAs film, resulting in a decrease in its fluorescence intensity. The present invention provides a new GaAs photonic crystal film preparation process.

[0064] The present invention relates to a micro-nanofabrication process for gallium arsenide-based one-dimensional / two-dimensional photonic crystal films. Silicon dioxide is grown on the surface of a gallium arsenide (GaAs) film as an etching mask to prepare the GaAs photonic crystal film, and the silicon dioxide layer remains after etching. This method effectively avoids damage to the GaAs-based photonic crystal film by wet etching solutions used in conventional processes, and can adjust the optical energy band wavelength of the GaAs-based photonic crystal film by controlling the growth thickness of the silicon dioxide layer. The silicon dioxide layer remains throughout the entire process, acting as a protective layer and mask to ensure the integrity of the periodic structure of the gallium arsenide-based one-dimensional / two-dimensional photonic crystal film.

[0065] Compared with the prior art, the photonic crystal film, preparation method and device of the present invention may have but are not limited to the following beneficial effects:

[0066] 1. Compared with the traditional preparation process, after using the mask layer as a mask template to etch the thin film on the substrate to form a photonic crystal structure, by retaining the surface mask template, the substrate surface is prevented from contacting the acidic corrosive solution, solving the problem of deterioration of fluorescence intensity due to corrosion of the substrate surface.

[0067] 2. On the basis of ensuring that the energy band shape of the photonic crystal remains unchanged, the energy band of the photonic crystal is controlled by adjusting the thickness of silicon dioxide to improve the device performance and application range.

[0068] 3. The mask layer is retained throughout the entire process and acts as a protective layer to ensure the integrity of the periodic structure of the one-dimensional / two-dimensional photonic crystal film. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:

[0070] Figure 1 A schematic diagram of the GaAs two-dimensional square lattice air-dielectric photonic crystal structure with a silicon dioxide layer on the surface to be prepared is shown.

[0071] Figure 2 The figure shows the relationship between the silicon dioxide thickness on the GaAs surface (horizontal axis) and the wavelength and quality factor of the optical band structure Γ of the photonic crystal calculated by the wave optics module of the COMSOL multi-physics simulation software. Figure 2 A shows the variation of energy band with silicon dioxide thickness; Figure 2 B shows the quality factor as a function of silicon dioxide thickness.

[0072] Figure 3 A schematic structural diagram of the photonic crystal film of the present invention prepared in Example 1 is shown. DETAILED DESCRIPTION

[0073] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings. However, it should be understood that these embodiments are only used for more detailed and specific description and should not be understood as limiting the present invention in any form.

[0074] This section provides a general description of the materials and experimental methods used in the experiments of the present invention. Although many of the materials and procedures used to achieve the purposes of the present invention are well known in the art, the present invention is described herein in as much detail as possible. It will be understood by those skilled in the art that, unless otherwise specified, the materials and procedures used in the present invention are well known in the art.

[0075] Example 1

[0076] This embodiment is an exemplary description of the photonic crystal film and the preparation method thereof of the present invention.

[0077] The photonic crystal film of the present invention, such as Figure 1 and 3 As shown, from bottom to top, it includes: a substrate and a mask layer located on the substrate; wherein: the mask layer is etched on the substrate to form a photonic crystal periodic structure pattern; the photonic crystal film also includes an air cavity area separated by the photonic crystal periodic structure pattern; the structure of the photonic crystal periodic structure pattern is a one-dimensional photonic crystal periodic structure pattern and / or a two-dimensional photonic crystal periodic structure pattern.

[0078] In this embodiment, the material of the substrate is InGaP, and the thickness is 180 nm. The material of the mask layer is silicon dioxide, and the thickness is 100 nm. The period of the photonic crystal is 450 nm, and the cross-sectional shape of the air cavity area is a square, and the side length of the air square is 100 nm.

[0079] The photonic crystal film fabrication method involves growing a silicon dioxide layer on the surface of an InGaP film using a deposition technique as an etching mask. The photonic crystal pattern is then transferred from the silicon dioxide layer to a GaAs film using an etching technique, forming the InGaP photonic crystal film structure. Preserving the surface SiO2 layer during the InGaP photonic crystal film fabrication process prevents corrosion damage to the InGaP film surface caused by wet etching solutions used in conventional fabrication methods. This ensures that the luminescence quality of the InGaP photonic crystal film is not affected by the etching solution, significantly simplifying the process.

[0080] The specific steps include:

[0081] (1) A 100 nm layer of silicon dioxide was grown on the surface of a 180 nm thick GaAs film using inductively coupled plasma enhanced chemical vapor deposition (ICPPECVD) technique, which had sufficient strength to act as an etching mask. The growth time was 5 min.

[0082] (2) Subsequently, a photoresist is applied to the silicon dioxide mask layer and photolithography is performed to form a photoresist pattern having a one-dimensional or two-dimensional periodic structure pattern. The photonic crystal period is 450 nm, and the air square grid has a side length of 100 nm. In the photoresist pattern having the photonic crystal periodic structure pattern, the area not protected by the photoresist is a square pattern, which is also the portion that is etched away in the photolithography step. In a subsequent etching process, the square pattern portion is also etched away, forming a square cavity in the periodic photonic crystal structure.

[0083] (3) Based on the photoresist pattern in the previous step, a photonic crystal pattern is etched on the silicon dioxide mask layer using inductively coupled plasma (ICP) etching technology. The etching time is 7 minutes.

[0084] (4) Then, the photoresist on the silicon dioxide mask layer is removed by performing a stripping process using an inductively coupled plasma (ICP) etching technique;

[0085] (5) Finally, the silicon dioxide layer with the surface pattern formed was used as a mask to etch the photonic crystal pattern on the InGaP film again using the inductively coupled plasma (ICP) etching technique. The etching time was 45 s.

[0086] (6) During the entire process, the silicon dioxide layer is not removed but is completely retained as a mask layer, and the energy band position of the photonic crystal finally obtained is precisely controlled by adjusting the SiO2 growth thickness in step (1) without affecting its energy band shape, thereby improving the application range of the device.

[0087] Example 2

[0088] This embodiment adjusts the thickness of the mask layer based on the photonic crystal film preparation method of Example 1, so as to illustrate the effect of changing the thickness of the mask layer on regulating the energy band position.

[0089] like Figure 2 As shown, the optical energy band of the photonic crystal film described in Example 1 is simulated and calculated using the wave optics module of COMSOL Mutiphysics multi-physics field simulation software (abbreviated as COMSOL or COMSOL software).

[0090] The specific steps include:

[0091] (1) Geometric modeling was performed in the wave optics module of COMSOL Multiphysics multi-physics simulation software. The geometric parameters were the same as those of the photonic crystal film structure described in Example 1: the substrate material in the example was InGaP (refractive index 3.602) with a thickness of 180 nm; the mask layer was made of silicon dioxide with a thickness set as a variable parameter; the period of the photonic crystal was 450 nm, and the cross-sectional shape of the air cavity region was a square with a side length of 100 nm. The refractive index of each material was taken from the refractive index data provided by this simulation software.

[0092] (2) Then, the optical energy band simulation calculation is performed on the above geometric modeling, wherein the thickness of the silicon dioxide mask layer is set as a variable parameter with a range of 0nm to 100nm and a step size of 5nm. The characteristic frequency is solved for each silicon dioxide mask layer thickness, and the intrinsic characteristic frequency range is set to 600nm to 700nm. The effect is to calculate the optical energy band of the photonic crystal film structure described in Example 1 within the range of 600nm to 700nm.

[0093] (3) Finally, observe the "wavelength" and "quality factor" data in the simulation calculation results and obtain Figure 2 As shown in Figure 2, the energy band wavelength and quality factor change with the thickness of silicon dioxide. Figure 2 The conclusion is that when the thickness of the silicon dioxide mask layer on the substrate surface changes from 0nm to 100nm, the wavelength of the photonic crystal film band redshifts by 29nm, and the order of magnitude of its quality factor remains unchanged.

[0094] Examples 3 to 5

[0095] Examples 3 to 5 are other exemplary descriptions of the photonic crystal film of the present invention and the effect of changing the thickness of the mask layer on regulating the energy band position.

[0096] The photonic crystal films prepared in Examples 3 to 5 are the same as those in Example 1 in terms of steps and conditions for preparing the same films, except for the selection of the contents listed in Table 1 below.

[0097] Table 1 Effect of changes in the thickness of the photonic crystal films and their mask layers prepared in Examples 3 to 5 on the regulation of the energy band position

[0098]

[0099] As can be seen from Table 1, the photonic crystal films of the present invention have good optical energy bands and quality factors, and the energy band positions of the photonic crystals can be precisely controlled by adjusting the thickness of silicon dioxide, while ensuring the integrity of the periodic structure of the one-dimensional / two-dimensional photonic crystal films.

[0100] Although the effects of some embodiments are shown above, those skilled in the art should understand that, according to the concept of the present invention, other embodiments described above, whose effects are not specifically shown, or other technical solutions of the present invention not shown in the embodiments, can also achieve the following technical effects described in the Summary of the Invention, which are equivalent to those of the embodiments:

[0101] 1. Compared with the traditional preparation process, after using the mask layer as a mask template to etch the thin film on the substrate to form a photonic crystal structure, by retaining the surface mask template, the substrate surface is prevented from contacting the acidic corrosive solution, solving the problem of deterioration of fluorescence intensity due to corrosion of the substrate surface.

[0102] 2. On the basis of ensuring that the energy band shape of the photonic crystal remains unchanged, the energy band of the photonic crystal is controlled by adjusting the thickness of silicon dioxide to improve the device performance and application range.

[0103] 3. The mask layer is retained throughout the entire process and acts as a protective layer to ensure the integrity of the periodic structure of the one-dimensional / two-dimensional photonic crystal film.

[0104] Although the present invention has been described to a certain extent, it is obvious that appropriate changes in various aspects can be made without departing from the spirit and scope of the present invention. It is understood that the present invention is not limited to the embodiments described, but belongs to the scope of the claims, which includes equivalent replacements of each factor described.

Claims

1. A photonic crystal film, characterized in that: The photonic crystal film comprises, from bottom to top, a substrate and a mask layer deposited on the surface of the substrate; wherein: The mask layer is etched on the substrate to form a photonic crystal periodic structure pattern; The photonic crystal film further includes air cavity regions spaced apart in the photonic crystal periodic structure pattern; Preferably, the structure of the photonic crystal periodic structure pattern is a one-dimensional photonic crystal periodic structure pattern and / or a two-dimensional photonic crystal periodic structure pattern.

2. The photonic crystal film according to claim 1, wherein: The material of the substrate is selected from one or more of the following: gallium arsenide, indium phosphide, InGaP, AlGaAs, silicon, gallium nitride, glass / fused silica, preferably selected from one or more of the following: gallium arsenide, InGaP, AlGaAs, indium phosphide, more preferably gallium arsenide and / or InGaP; and / or The thickness of the substrate is 100-500 nm, preferably 150-400 nm, and more preferably 150-200 nm.

3. The photonic crystal film according to claim 1 or 2, characterized in that: The material of the mask layer is selected from one or more of the following: silicon dioxide, aluminum oxide, silicon nitride, hafnium oxide, chromium metal film, nickel metal film, preferably selected from one or more of the following: silicon dioxide, aluminum oxide, silicon nitride, most preferably silicon dioxide; The thickness of the mask layer is 500 nm or less, preferably 300 nm or less, more preferably 100 nm or less; and / or The thickness of the mask layer can be adjusted, and as the thickness of the mask layer is adjusted, the energy band wavelength of the photonic crystal film shifts accordingly; Preferably, the range of the corresponding shift of the energy band wavelength is 10 to 80 nm, more preferably 10 to 50 nm, further preferably 10 to 30 nm, and further preferably 10 to 29 nm.

4. The photonic crystal film according to any one of claims 1 to 3, characterized in that: The period of the photonic crystal is 250 to 600 nm, preferably 300 to 500 nm, more preferably 350 to 450 nm; and / or The cross-sectional shape of the air chamber area is selected from one or more of the following: square, circle, triangle, ellipse, hexagon, preferably selected from one or more of the following: square, circle, triangle, most preferably square; Preferably, the cross-sectional area of ​​the air chamber region is 8000 nm 2 ~160000nm 2 , more preferably 9000nm 2 ~122500nm 2 , more preferably 10000nm 2 ~22500nm 2 ; More preferably, when the cross-sectional shape of the air cavity region is a square, the side length of the cross-sectional shape of the air cavity region is 90 to 400 nm, more preferably 95 to 350 nm, and further preferably 100 to 150 nm.

5. The method for preparing the photonic crystal thin film according to any one of claims 1 to 4, characterized in that: The method comprises the following steps in sequence: 1) growing the mask layer on the substrate; 2) spin-coating a photoresist on the mask layer and performing photolithography to form a photoresist pattern having a photonic crystal periodic structure pattern, and etching the photonic crystal periodic structure pattern; 3) removing the photoresist on the mask layer; and 4) Using the mask layer as a mask plate, etching a pattern having a photonic crystal periodic structure on the substrate, and retaining the mask layer.

6. The method according to claim 5, characterized in that In the step 1): The method of growing the mask layer is selected from one or more of the following: inductively coupled plasma enhanced chemical vapor deposition, electron beam evaporation, sputtering deposition, atomic layer deposition, thermal oxidation, and wet chemical deposition, preferably selected from one or more of the following: inductively coupled plasma enhanced chemical vapor deposition, electron beam evaporation, sputtering deposition, and atomic layer deposition, and most preferably inductively coupled plasma enhanced chemical vapor deposition; and / or The time for growing the mask layer is 3 minutes to 30 minutes, preferably 4 minutes to 20 minutes, and more preferably 5 minutes to 7 minutes.

7. The method according to claim 5 or 6, characterized in that In the step 2): The etching method of the photonic crystal periodic structure pattern is selected from one or more of the following: inductively coupled plasma etching, reactive ion etching, wet etching, focused ion beam etching, laser induced etching, preferably selected from one or more of the following: inductively coupled plasma etching, reactive ion etching, focused ion beam etching, most preferably inductively coupled plasma etching; and / or The etching time of the photonic crystal periodic structure pattern is 5 minutes to 30 minutes, preferably 6 minutes to 20 minutes, and more preferably 7 minutes to 15 minutes.

8. The method according to any one of claims 5 to 7, characterized in that In the step 4): The etching method on the substrate is selected from one or more of the following: inductively coupled plasma etching, reactive ion etching, wet etching, focused ion beam etching, laser induced etching, preferably selected from one or more of the following: inductively coupled plasma etching, reactive ion etching, focused ion beam etching, most preferably inductively coupled plasma etching; and / or The etching time on the substrate is 40s to 140s, preferably 42s to 120s, and more preferably 45s to 60s.

9. The method according to any one of claims 5 to 8, characterized in that The step 2) also includes the following steps: In a photoresist pattern having a photonic crystal periodic structure pattern, regions uncovered by the photoresist are etched to form air cavities in the periodic photonic crystal structure.

10. A device for optical communication or optoelectronics, characterized in that: The device comprises a photonic crystal film according to any one of claims 1 to 4; Preferably, the device for optical communication is selected from one or more of the following: photonic crystal laser, photonic crystal waveguide, photonic crystal resonant cavity, photonic crystal filter, slow light device; and / or Preferably, the optoelectronic device is selected from one or more of the following: a light detector, a light modulator, a photonic crystal solar cell, a quantum light source, and a surface plasmon photonic crystal.

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