Artificial in-plane birefringence device based on antimony selenide and preparation method of artificial in-plane birefringence device

Abstract

The invention belongs to the technical field of birefringence device preparation, and particularly relates to an antimony selenide-based artificial in-plane birefringence device, which comprises a substrate layer and a phase change material layer, the phase change material layer is provided with grid peaks and grid valleys which are alternately arranged, the grid peaks are in a crystalline state, and the grid valleys are in an amorphous state. The device adopts a special phase state alternating grating structure, not only retains the geometric appearance periodicity of the grating, but also realizes the periodicity of an amorphous state and a crystalline state, realizes an adjustable birefringence coefficient within a range of 0.08-0.4 in a visible light wave band, and has an average transmittance of more than 70%. The bottleneck problems that an existing birefringent device cannot be continuously modulated in the visible light range and is poor in flexible programming performance and reconstruction performance are fundamentally solved, and the prepared device has the advantages of being large and continuously adjustable in phase delay amount, continuously adjustable in slow axis angle, low in loss, easy to machine, reliable and the like.

Description

Technical Field

[0001] The invention relates to the technical field of birefringence device preparation, in particular to an antimony selenide-based artificial in-plane birefringence device and a preparation method thereof. Background Art

[0002] With the development of nonlinear optics, optical communications, polarized information processing and other fields, people have a stronger demand for devices with adjustable large birefringence in the visible light band. At present, typical birefringence devices can be divided into two categories: artificial metasurfaces and natural two-dimensional van der Waals crystals. The former integrates functions such as birefringence control and optical multiplexing by regulating the polarization coupling between the incident light and the artificial micro-nanostructure, and is therefore widely sought after. However, the metasurface structure cannot be reconstructed once prepared, and the metasurface working in the visible light band requires a smaller nanostructure. Therefore, the complex structural unit design and high production cost limit the practical application of artificial metasurfaces. The latter relies on its intrinsic crystal structure with in-plane asymmetry to achieve large in-plane birefringence characteristics. However, the adhesion between its layers is extremely weak and it is easy to fail in practical applications. In addition, its birefringence characteristics are closely related to its number of layers. Most two-dimensional van der Waals materials must be prepared by mechanical exfoliation, which places extremely high demands on its preparation process and is difficult to apply on a large scale.

[0003] At present, it is extremely challenging to make a device with adjustable large in-plane birefringence in the visible light band. The difficulties are mainly reflected in the material selection and preparation process: (1) The birefringence properties of existing two-dimensional materials are closely related to their number of layers, and it is difficult to accurately control them through mechanical peeling. (2) For metasurface devices, working in the visible light band requires a periodic structure less than 250nm, which is a challenge in experimental preparation.

[0004] In view of this, there is an urgent need to provide a new device with adjustable large in-plane birefringence in the visible light band, a device with large phase delay, continuously adjustable slow axis angle, easy processing and reliability. Summary of the invention

[0005] The purpose of the present invention is to provide an artificial in-plane birefringence device based on antimony selenide and a preparation method thereof, and the main problem to be solved is that the existing natural two-dimensional birefringence crystal materials and metasurface devices cannot be continuously modulated in the visible light range, and have poor flexible programming performance and reconstruction performance.

[0006] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0007] The present invention provides an artificial in-plane birefringence device based on antimony selenide, characterized in that it comprises a substrate layer and a phase change material layer; a grating structure formed by periodic arrangement of amorphous and crystalline states is arranged on the phase change material layer; the phase change material layer is a one-dimensional chalcogenide phase change material with an intrinsic crystal structure having an in-plane asymmetry; and the grating structure is a deep sub-wavelength surface periodic structure formed by self-assembly of the phase change material surface through laser direct writing.

[0008] Furthermore, in the above artificial in-plane birefringence device:

[0009] The one-dimensional chalcogenide phase change material is Sb2Se3;

[0010] The substrate is quartz glass with a thickness of 0.5 mm;

[0011] The phase change material layer has a thickness of 40 to 200 nm.

[0012] Furthermore, in the above-mentioned artificial in-plane birefringence device: the grating structure formed by the periodic arrangement of amorphous and crystalline Sb2Se3 has an alternating period of 180 to 400 nm.

[0013] The present invention also provides a method for preparing an artificial in-plane birefringence device based on antimony selenide, comprising the following steps:

[0014] S1 uses deionized water and ethanol to ultrasonically clean the quartz glass used as the substrate for fifteen minutes, and then quickly dries it.

[0015] S2 uses magnetron sputtering equipment to install the Sb2Se3 target in the RF power target.

[0016] S3 performs vacuum treatment on the sputtering chamber of the magnetron sputtering equipment until the required vacuum degree is reached in the chamber.

[0017] S4 provides argon atmosphere into the sputtering chamber and controls the argon flow rate until the working pressure is reached in the chamber.

[0018] S5 controls the power of the radio frequency power supply to deposit an amorphous phase change material film on the substrate.

[0019] S6 uses a femtosecond laser processing system to perform laser direct writing on specific areas of the phase change material film, and induces light intensity redistribution in the optical near field through the far field, forming a grating structure in which amorphous and crystalline states are periodically alternating.

[0020] Furthermore, the vacuum degree required for S3 is 2×10 -4 Pa~3×10 -4 Pa, S4, argon flow rate is 60.0sccm, working pressure is 2.5×10 -1In Pa, S5, the sputtering conditions are: the sputtering power of the Sb2Se3 target is 60W, the target-substrate distance is 22.5cm, and the working temperature is room temperature. Under the above conditions, pre-sputtering is performed for 5min to remove the oxide layer and impurities on the surface of the target material, and then the sample baffle is opened and sputtering is performed at a rate of 8nm / min for 5 to 25min.

[0021] Furthermore, in S6, the piezoelectric displacement stage is controlled by a computer program to achieve pattern processing. The laser wavelength is 515 nm, the repetition frequency is 200 kHz, the numerical aperture of the objective lens is 0.8, the pulse width is 273 fs, and the laser power density ranges from 1×10 7 ~1×10 11 W / m 2 , the laser energy distribution is Gaussian distribution.

[0022] Furthermore, in S6, the required processing parameters are: the moving speed adjustment range of the piezoelectric displacement stage is 50 to 200 nm / s, the number of pulses is 100 to 800 times, and the processing point spacing is 10 to 50 nm.

[0023] In the present invention, the substrate is used as a supporting structure to carry an artificial in-plane birefringent metasurface. The phase change material layer is a grating structure formed by periodic arrangement of amorphous and crystalline Sb2Se3. A protective layer can be optionally provided on the outer surface of the phase change material layer to maintain the effect of the metasurface.

[0024] In the design and manufacturing process of artificial in-plane birefringence devices, traditional single crystal materials such as sapphire and calcite have the characteristics of large volume and low birefringence coefficient, which makes it difficult to play a role in micro-nano size; natural two-dimensional van der Waals crystal materials rely on their asymmetric intrinsic crystal structure in the plane to achieve large birefringence characteristics. However, the adhesion between its layers is extremely weak, and it is easy to fail in practical applications. In addition, its birefringence characteristics are closely related to its number of layers. Most two-dimensional van der Waals materials must be prepared by mechanical exfoliation, which puts extremely high demands on its preparation process and is difficult to prepare on a large scale. However, processing technologies based on ultraviolet lithography, electron beam lithography, nanoimprinting, focused ion beam milling, etc. have the disadvantages of inflexible processing, complicated steps, high cost, and inability to reconstruct. The metasurfaces formed by these technologies cannot be changed once they are formed, which makes these devices difficult to modulate continuously and have no reconstructability. Therefore, the design and processing of artificial in-plane birefringence devices have encountered bottlenecks. In view of the above problems, the technical solution of the present invention uses a thin, programmable phase change material film as the basic material, uses a femtosecond laser processing system with high flexibility and high processing precision for processing, and experimentally prepares a device with high in-plane birefringence characteristics, thereby solving the above problems. The specific solution is:

[0025] For artificial in-plane birefringence devices, the ideal device should have high transparency, which means that the base material should have low reflection and extinction coefficients in the visible band. At the same time, the base material should have the characteristics of simple preparation, easy processing, and high stability. In order to ensure the practical application of the device in a visible environment, the inventor selected the sulfur-based phase change material Sb2Se3 through a large number of first-principles calculations and optical simulations. This material has an average transmittance of more than 70% in the visible band, which shows that it meets the transparency requirements of artificial in-plane birefringence devices. At the same time, this material also has the characteristics of simple preparation, easy processing, and high stability. Therefore, Sb2Se3 is an excellent base material for artificial in-plane birefringence devices.

[0026] From the processing technology, the metasurface structure with excellent birefringence performance should be a uniform and periodically stable grating structure. In order to achieve this processing goal, the inventors conducted a lot of experimental explorations and finally obtained a grating structure with excellent birefringence performance. The inventors prepared a uniform amorphous phase change material film on quartz glass by magnetron sputtering. Using a femtosecond laser processing system with the advantages of flexible processing, high processing precision and low processing cost, based on the principle of far-field induced local enhancement of near-field light field, a deep subwavelength structure formed by periodic arrangement of amorphous and crystalline Sb2Se3 parallel to the laser polarization direction was generated on the surface of the phase change material film, and this structure responded to visible light. After characterization by a birefringence microscope, it was found that the processed area had an adjustable birefringence delay of 1 to 15 nm, a slow axis angle that could be modulated from 0 to 360°, and the birefringence area was reconfigurable.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention fundamentally solves a series of bottleneck problems such as the difficulty of continuous modulation, high processing cost, and unreliability of birefringent devices based on two-dimensional van der Waals materials and artificial metasurfaces, and provides an artificial in-plane birefringent device and a preparation method thereof. The artificial in-plane birefringent device prepared by the present invention has the advantages of large phase delay, continuously adjustable slow axis angle, easy processing, and reliability.

[0029] 2. Based on the sulfur phase change material Sb2Se3 that conforms to the stoichiometric ratio, the present invention explains the principle of periodic structure on the surface of Sb2Se3 by combining first-principles calculation, optical simulation and thermodynamic simulation, and designs and prepares an artificial in-plane birefringence device based on Sb2Se3 that is generated under the crystallization energy threshold, can be self-assembled, has a deep sub-wavelength period, has minimal surface damage, has a high birefringence coefficient, and has high transmittance in the visible light band. This is something that previous birefringence devices based on two-dimensional van der Waals materials and artificial metasurfaces could not achieve. By utilizing the non-volatile, phase-stable, and phase-switching capabilities of phase change materials, the metasurface is reconfigurable, programmable, and non-volatile, making it suitable for long-term use.

[0030] 3. The femtosecond laser processing system prepared a grating structure formed by the periodic arrangement of amorphous and crystalline Sb2Se3. Compared with micro-nano processing technologies such as nanoimprinting, lithography, electron beam lithography, and focused ion beam milling, the preparation method of the present invention has the advantages of flexibility, low cost, and large-area processing. The formed metasurface also has reconstruction performance.

[0031] Of course, any product implementing the present invention does not necessarily need to achieve all of the above advantages at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the preparation process of the present invention;

[0033] Figure 2 This is a scanning electron microscope image of the artificial in-plane birefringence device prepared by femtosecond laser irradiation in this patent;

[0034] Figure 3 The relationship between the phase delay and energy produced by the birefringent device in this patent;

[0035] Figure 4 The relationship between the phase delay amount and the number of pulses produced by the birefringence device in this patent;

[0036] Figure 5 This is a birefringence microscope image of the birefringence device in this patent with adjustable slow axis angle;

[0037] Figure 6 Schematic diagram of the femtosecond laser processing system in this patent. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 technical personnel in this field without creative work are within the scope of protection of the present invention.

[0039] An artificial in-plane birefringence device based on antimony selenide comprises a substrate layer and a phase change material layer; a grating structure formed by a periodic arrangement of amorphous and crystalline Sb2Se3 is arranged on the phase change material layer; the phase change material layer is a one-dimensional chalcogenide phase change material with an intrinsic crystal structure having an in-plane asymmetry; the grating structure is a structure formed by self-assembly of the phase change material surface through laser direct writing.

[0040] The substrate layer is quartz glass;

[0041] The phase change material layer is Sb2Se3, and the thickness is 40 to 200 nm.

[0042] The grating structure is formed by the periodic arrangement of amorphous and crystalline Sb2Se3, and its alternating period is 180 to 400 nm.

[0043] The specific embodiments of the present invention are as follows:

[0044] Example 1

[0045] Substrate pretreatment before sputtering experiment: Before placing the quartz glass substrate into the vacuum chamber, ultrasonic cleaning was performed with acetone, anhydrous ethanol, and distilled water in sequence for 15 min and then blown dry.

[0046] Substrate preheating and pre-sputtering: When the vacuum degree of the vacuum chamber reaches 2x10 -4 Pa, in order to remove the oxide layer and adsorbed impurities on the surface of the Sb2Se3 target, the target was heated to 400 ℃ under an argon gas flow rate of 60.0 sccm and a working pressure of 2.5×10 -1 Pre-sputtering for 5 min under the condition of Pa.

[0047] The Sb2Se3 target was used as the target source, argon gas was used as the discharge gas, the sputtering power of the Sb2Se3 target was controlled, and the quartz glass was used as the substrate. The Sb2Se3 film was deposited on the substrate under the set sputtering conditions; the sputtering conditions were: the vacuum degree was 2×10 -4 Pa, working pressure is 2.5×10 -1 Pa, the target substrate distance is 22.5cm, and the argon flow rate is 60.0sccm; the RF sputtering power of the Sb2Se3 target is controlled to be 60W, and the deposition time is 5min.

[0048] Through the femtosecond laser processing system, laser direct writing is performed on specific areas of the Sb2Se3 film under set conditions; the writing conditions are: laser wavelength of 515nm, repetition frequency of 200KHz, numerical aperture of the objective lens of 0.8, number of pulses of 800, polarization of horizontal polarization, and movement speed of the piezoelectric displacement stage of 200nm / S. Through the processing program, the laser direct writing period is controlled to be 250nm. The grating structure formed by the periodic arrangement of amorphous and crystalline Sb2Se3 can be processed, and the period of this structure is 180nm. At this time, the area appears black under an optical microscope, and the slow axis angle is 170° and the delay amount is 14nm under a birefringence microscope.

[0049] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An artificial in-plane birefringence device based on antimony selenide, comprising a substrate layer and a phase change material layer, characterized in that: The phase change material layer is provided with alternatingly arranged gate peaks and gate valleys, the gate peaks are in a crystalline state, the gate valleys are in an amorphous state, the phase change material layer is a one-dimensional sulfur-based phase change material with an intrinsic crystal structure with in-plane asymmetry, the material of the phase change material layer is Sb2Se3, the material of the substrate is quartz glass, the thickness of the substrate is 0.5mm, the thickness of the phase change material layer is 40 to 200nm, and the spectral average transmittance of the phase change material layer in the target band is ≥70%.

2. The artificial in-plane birefringence device based on antimony selenide according to claim 1, characterized in that: The grating structure is a deep subwavelength surface periodic structure formed by self-assembly of the phase change material surface through far-field induced near-field optical effect. The material constituting the grating structure is only one-dimensional sulfur-based phase change material Sb2Se3. The depth of the grating structure is 5 to 20 nm, and the grating period is 180 to 400 nm.

3. A method for preparing an artificial in-plane birefringence device based on antimony selenide, characterized in that: The steps include: S1: Depositing a phase change material layer on a substrate by magnetron co-sputtering technology to obtain a deposited amorphous phase change material film; S11: The quartz glass substrate is ultrasonically cleaned for fifteen minutes using deionized water and ethanol, and then quickly dried; S12: Using magnetron sputtering equipment, install the Sb2Se3 target in the RF power target; S13: evacuating the sputtering chamber of the magnetron sputtering equipment until the required vacuum degree is reached in the chamber; S14: providing argon atmosphere into the sputtering chamber and controlling the argon flow rate until the chamber reaches a working pressure; S15: controlling the power of the radio frequency power supply to deposit an amorphous phase change material thin film on the substrate; S2: A femtosecond laser processing system is used to perform laser direct writing on a specific area of ​​the phase change material layer, and a far-field-induced optical near-field light intensity redistribution is performed to form a grating structure in which amorphous and crystalline states are periodically alternately arranged.

4. The method for preparing an artificial in-plane birefringence device based on antimony selenide according to claim 3, characterized in that: In S13, the required vacuum degree is 2×10 -4 Pa~3×10 -4 Pa.

5. The method for preparing an artificial in-plane birefringence device based on antimony selenide according to claim 3, characterized in that: In S14, the argon gas flow rate is 60.0 sccm and the working pressure is 2.5×10 -1 Pa.

6. The method for preparing an artificial in-plane birefringence device based on antimony selenide according to claim 3, characterized in that: In S15, the sputtering conditions are: the sputtering power of the Sb2Se3 target is 60W, the target-substrate distance is 22.5cm, and the working temperature is room temperature. Under the above conditions, pre-sputtering is performed for 5min to remove the oxide layer and impurities on the surface of the target material, and then the sample baffle is opened and sputtering is performed at a rate of 8nm / min for 5 to 25min.

7. The method for preparing an artificial in-plane birefringence device based on antimony selenide according to claim 3, characterized in that: The femtosecond laser is focused on the surface of the phase change material film, and the piezoelectric displacement stage is controlled by a computer program to achieve pattern processing. The laser wavelength is 515nm, the repetition frequency is 200KHz, the numerical aperture of the objective lens is 0.8, the pulse width is 273fs, and the laser power density range is 1×10 7 ~1×10 11 W / m 2 , the laser energy distribution is Gaussian distribution; the moving speed adjustment range of the piezoelectric translation stage is 50-200nm / s, the pulse number is 100-800 times, and the processing point spacing is 10-50nm.

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