A reconfigurable mid-infrared metasurface filter device based on indium tin oxide

Abstract

The application discloses a reconfigurable indium tin oxide-based mid-infrared metasurface filter device, which comprises a substrate, a dielectric layer and a metasurface structure unit arranged on the substrate in sequence; the metasurface structure unit is concentrically arranged with the dielectric layer and jointly forms a basic unit, and the basic unit is periodically arranged on the upper surface of the substrate; the material of the metasurface structure unit is indium tin oxide, so that the device can work stably for a long time under complex working conditions. Meanwhile, the amorphous phase has a relatively low refractive index and extinction coefficient in the mid-infrared wave band, which is beneficial to reducing the internal optical loss of the device. By adjusting the key geometric parameters of the metasurface structure unit, including thickness h , radius R and arrangement period p , the filter range can be flexibly regulated. In addition, the reversible switching between the amorphous phase and the crystal phase of ITO can be driven by external excitation, so that the filter range of the device can be switched, and dynamic regulation between the two wave bands of 6-7 mu m and 8-10 mu m can be realized.

Description

Technical Field

[0001] This invention relates to the fields of oxide materials and optical devices, specifically to a reconfigurable mid-infrared metasurface filter device based on indium tin oxide. Background Technology

[0002] The mid-infrared band (typically 3-25 μm) covers the atmospheric window, molecular characteristic absorption region, and the main bands of thermal radiation, and has significant application value in fields such as environmental gas monitoring, spectral analysis, and infrared imaging. However, traditional imaging spectral systems mostly rely on electrically driven filter wheels to achieve wavelength switching. These mechanical filter structures are large in size and have many moving parts, placing high demands on satellite system stability and spatial layout, thus restricting the development of spectral systems towards compactness, lightweight design, and high reliability.

[0003] In recent years, the development of metasurface filters with reconstruction capabilities has provided a new technological approach for spectral systems. A metasurface is a two-dimensional nanostructure surface composed of periodically arranged subwavelength-scale structural units. By precisely designing the material properties and geometric parameters of these structural units, the amplitude, phase, polarization, and other characteristics of incident electromagnetic waves can be flexibly controlled, gradually becoming an important technological path for the development of micro- and nano-optical devices. Among these, metasurface-based filtering devices utilize the electromagnetic resonance effect generated by their structural units at specific frequencies to achieve selective transmission or reflection of electromagnetic waves in the target wavelength band, thereby achieving the filtering purpose.

[0004] Existing technologies primarily utilize electrical, optical, or thermal modulation methods to achieve reconfigurable metasurfaces from various materials, such as metallic materials, two-dimensional materials, and liquid crystal materials, all of which have been used to achieve different forms of reconfigurable filtering effects. However, these materials suffer from high losses, poor compatibility with existing mature micro / nano fabrication processes, and insufficient environmental stability in practical applications, limiting their practical use under complex operating conditions or long-term operation. Therefore, there is an urgent need to develop a structural unit material with low losses, good process compatibility, and mechanical stability to meet the performance and reliability requirements under harsh environments. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a reconfigurable mid-infrared metasurface filter device based on indium tin oxide (ITO). The amorphous phase of ITO exhibits low refractive index and extinction coefficient in the mid-infrared band, along with excellent process compatibility, mechanical stability, and good adhesion to silicon substrates. This facilitates large-scale fabrication and allows for long-term stable operation under complex conditions. Furthermore, reversible switching between the amorphous and crystalline phases of ITO can be achieved through external stimulation, thereby altering its optical properties and achieving filtering effects across different wavelength bands.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A reconfigurable mid-infrared metasurface filter device based on indium tin oxide, the device comprising a substrate, on which a dielectric layer and metasurface structure units are sequentially disposed;

[0008] Among them, the metasurface structure unit and the dielectric layer are concentrically arranged to form a basic unit, and the basic unit is periodically arranged on the upper surface of the substrate.

[0009] The metasurface structural unit material is indium tin oxide (ITO), which is a combination of In₂O₃ and SnO₂, with a composition of (In₂O₃). x (SnO2) y , where 80 wt.%≤x≤95 wt.%, 5 wt.%≤y≤20 wt.%, x+y=100;

[0010] The ITO reversibly switches between an amorphous phase and a crystalline phase. When in the amorphous phase, the device filters in a wavelength range of 6-7 μm, and when in the crystalline phase, the device filters in a wavelength range of 8-10 μm.

[0011] The substrate is any one of CaF2, Al2O3 and SiO2 materials;

[0012] The dielectric layer is an optical resonant cavity made of Si, with a cylindrical geometry, a thickness of 800 nm, and a radius ranging from 1100 to 1300 nm.

[0013] The metasurface structural unit material is ITO, and its geometry is cylindrical with a thickness of [missing information]. h The range is 600-1000 nm, radius R It is consistent with the dielectric layer, i.e., the range is 1100-1300 nm.

[0014] The metasurface structural units and the dielectric layer are concentrically arranged to form a basic unit, which is periodically arranged on the upper surface of the substrate. p The range is 3.5-4.5 μm.

[0015] The overall thickness of the reconfigurable mid-infrared metasurface filter device is typically in the range of micrometers to millimeters, with a preferred thickness range of 100-600 μm.

[0016] In the device, if ITO is an amorphous phase, when h When the wavelength changes from 600 nm to 1000 nm, the filtering wavelength of the device changes from 6.3-6.5 μm to 6.3-7 μm; when RWhen the wavelength changes from 1100 nm to 1300 nm, the filtering wavelength of the device changes from 6.2-6.5 μm to 6.5-6.9 μm; when p When the wavelength changes from 3.5 μm to 4.5 μm, the filtering wavelength of the device changes from 6-6.4 μm to 6.3-6.7 μm.

[0017] The device, such as ITO, is a crystalline phase, when h When the wavelength changes from 600 nm to 1000 nm, the filtering wavelength of the device changes from 8.5-9 μm to 8.5-10 μm; when R When the wavelength changes from 1100 nm to 1300 nm, the filtering wavelength of the device changes from 8.4-9 μm to 8-10 μm; when p When the wavelength changes from 3.5 μm to 4.5 μm, the filtering wavelength of the device changes from 8-10 μm to 8.8-9.5 μm.

[0018] The ITO has a crystallization temperature above 250 ℃ and a melting point above 1500 ℃, exhibiting good film stability and effectively improving device stability.

[0019] The reversible switching between the amorphous phase and the crystalline phase of the metasurface structural unit can be achieved by external excitation; the external excitation includes, but is not limited to, laser pulses or electrical pulses.

[0020] During the transition from amorphous to crystalline phase, the temperature of the metasurface structural unit is raised to the crystallization temperature range by applying an external excitation with low to medium energy density and long duration.

[0021] Use a 30-100mW laser pulse, or a 0.6-3V electrical pulse.

[0022] During the transition from crystalline to amorphous phase, by applying a high-energy-density transient external excitation, the local temperature of the metasurface structure unit is raised to above its melting temperature, and rapid cooling is achieved after the excitation is removed, thereby forming an amorphous phase structure.

[0023] Use a 50-150mW laser pulse, or a 1.5-5V electrical pulse.

[0024] The fabrication methods for each layer of the device include, but are not limited to, physical vapor deposition (PVD), chemical vapor deposition (CVD), or atomic layer deposition (ALD).

[0025] The beneficial effects of this invention are:

[0026] The reconfigurable mid-infrared metasurface filter device based on indium tin oxide (ITO) proposed in this invention can achieve filtering effects on different wavelength bands through reversible switching of the structural unit phase structure, overcoming the problems of large size and low precision of traditional mechanical filter wheel structures. The specific mechanism is as follows: ITO can reversibly switch between amorphous and crystalline phases under external excitation. The two phases have significantly different optical properties in the mid-infrared band, thus enabling the device to filter in the 6-7 μm wavelength range when the structural unit is amorphous, and in the 8-10 μm wavelength range when it is crystalline.

[0027] The reconfigurable mid-infrared metasurface filter device based on indium tin oxide proposed in this invention can be tuned by multiple parameters, including thickness. h ,radius R and layout cycle p It allows for flexible adjustment of the filter center wavelength and bandwidth, thereby achieving tunability of the filtering range; and the composition control range of indium tin oxide material is relatively wide, enabling the device to have a wider range of application scenarios.

[0028] The indium tin oxide thin film material proposed in this invention for reconfigurable metasurface filter devices exhibits good mechanical stability and substrate adhesion; moreover, it is chemically stable, with a crystallization temperature above 250 ℃ and a melting point above 1500 ℃. Therefore, the device exhibits high stability, is not prone to performance degradation, and is suitable for long-term stable operation under complex conditions. Attached Figure Description

[0029] Figure 1 The graphs show the real and imaginary parts of the dielectric constant for the amorphous and crystalline phases of ITO.

[0030] Figure 2 This is a schematic diagram of the reconfigurable metasurface filter device structure proposed in this invention.

[0031] Figure 3 The reflection spectrum of ITO-based metasurface filter devices varies with the thickness of structural units. h The change graph.

[0032] Figure 4 The reflection spectrum of ITO-based metasurface filter devices varies with the radius of the structural unit. R The change graph.

[0033] Figure 5 The reflection spectrum of ITO-based metasurface filter devices varies with the array arrangement period. p The change graph. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings.

[0035] This invention discloses a reconfigurable mid-infrared metasurface filter device based on indium tin oxide, such as... Figure 2 As shown, it includes a substrate 1, on which a dielectric layer 2 and a metasurface structure unit 3 are sequentially disposed;

[0036] Among them, the metasurface structure unit 3 and the dielectric layer 2 are concentrically arranged to form a basic unit, and the basic unit is periodically arranged on the upper surface of the substrate 1.

[0037] The dielectric layer 2 is an optical resonant cavity made of Si, with a cylindrical geometry, a thickness of 800 nm, and a radius ranging from 1100 to 1300 nm.

[0038] The metasurface structure unit 3 is made of ITO, and its geometry is cylindrical with a thickness of [missing information]. h The range is 600-1000 nm, radius R It is consistent with the dielectric layer, i.e., the range is 1100-1300 nm.

[0039] The metasurface structure unit 3 and the dielectric layer 2 are concentrically arranged to form a basic unit, which is periodically arranged on the upper surface of the substrate 1. p The range is 3.5-4.5 μm.

[0040] The present invention will be further illustrated below with specific embodiments.

[0041] Example 1

[0042] This embodiment is based on a reconfigurable mid-infrared metasurface filter device of ITO (In2O3:SnO2= 90:10 wt.%), and the specific implementation process is as follows:

[0043] The real and imaginary parts of the dielectric function curves for ITO amorphous and crystalline phases are shown below. Figure 1 As shown; the reconfigurable mid-infrared metasurface filter device structural unit based on ITO is as follows: Figure 2 As shown, substrate 1 is made of CaF2; dielectric layer 2 is cylindrical, made of Si, with a radius of 1200 nm and a thickness of 800 nm; metasurface structural unit 3 is cylindrical, made of ITO, with a radius of... R 1200 nm; structural unit arrangement period p It is 4.5 μm. x and y The direction is set as a periodic boundary condition. z The direction is set to perfectly match the boundary conditions, the light source is a plane wave, and the incident direction is... z Negative direction of the axis.

[0044] The reflectance spectrum of the device varies with the thickness of metasurface structural unit 3.h Changes such as Figure 3 As shown, Figure 3 The reflection spectrum of a reconfigurable mid-infrared metasurface filter device based on ITO varies with the thickness of the structural unit. h The variation graph shows that the amorphous phase exhibits a significant reflection peak in the 6.3-7 μm range, allowing the device to perform filtering within this wavelength range; furthermore, its reflectivity in this range is significantly higher than that of the crystalline phase. However, the reflectivity in the 3-6.3 μm and 7-15 μm wavelength ranges is below 25% and 3% respectively, both exhibiting low reflection responses with a difference of up to 55% from the peak value. Therefore, the device can perform filtering within the 6.3-7 μm wavelength range. With increasing structural unit thickness, the peak reflectivity of the amorphous phase gradually increases, and the reflection wavelength range gradually widens. As the structural unit thickness increases... h At 1000 nm, the amorphous phase has a reflectivity of up to 80% at ~6.5 μm; while the crystalline phase has a reflectivity of 22% at ~9.2 μm, and the device can filter in the wavelength range of 8.5-10 μm.

[0045] Example 2

[0046] This embodiment is based on a reconfigurable mid-infrared metasurface filter device of ITO (In2O3:SnO2= 90:10 wt.%), and the specific implementation process is as follows:

[0047] The real and imaginary parts of the dielectric function curves for ITO amorphous and crystalline phases are shown below. Figure 1 As shown. The reconfigurable mid-infrared metasurface filter device structural unit based on ITO is as follows. Figure 2 The substrate 1 shown is made of CaF2; the dielectric layer 2 is cylindrical, made of Si, and has a thickness of 800 nm; the metasurface structure unit 3 is cylindrical, made of ITO, and has a thickness of [missing information]. h 800 nm; structural unit arrangement period p It is 4.5 μm. x and y The direction is set as a periodic boundary condition. z The direction is set to perfectly match the boundary conditions, the light source is a plane wave, and the incident direction is... z Negative direction of the axis.

[0048] The reflection spectrum of this device varies with the radius of the structural unit. R Changes such as Figure 4 As shown, Figure 4 The reflection spectrum of a reconfigurable mid-infrared metasurface filter device based on ITO varies with the radius of the structural unit. RThe variation graph shows that the amorphous phase exhibits a significant reflection peak in the 6.2-6.9 μm range, with a much higher reflectivity than the crystalline phase within this range. However, the reflectivity in the 3-6.2 μm and 6.9-15 μm bands is below 21% and 4% respectively, both exhibiting low reflectivity responses with a difference of up to 63% from the peak value. Therefore, the device can perform filtering in the 6.2-6.9 μm wavelength range. As the structural unit radius increases, the peak reflectivity of the amorphous phase gradually decreases. When the structural unit radius... R At a wavelength of 1100 nm, the amorphous phase exhibits a reflectivity as high as 84% ​​at ~6.3 μm. Furthermore, when the structural unit radius... R At a wavelength of 1300 nm, the reflectivity of the crystal phase at ~9.3 μm is 28%, at which point the device can filter in the wavelength range of 8-10 μm.

[0049] Example 3

[0050] This embodiment is based on a reconfigurable mid-infrared metasurface filter device of ITO (In2O3:SnO2= 90:10 wt.%), and the specific implementation process is as follows:

[0051] The real and imaginary parts of the dielectric function curves for ITO amorphous and crystalline phases are shown below. Figure 1 As shown, Figure 1 (a) represents the real part of the dielectric function for the amorphous and crystalline phases of ITO. Figure 1 (b) represents the imaginary part of the dielectric function of the amorphous and crystalline phases of ITO. The dielectric functions of the two phases differ significantly in the mid-infrared band.

[0052] ITO-based reconfigurable mid-infrared metasurface filter device structural unit, such as Figure 2 As shown, substrate 1 is made of CaF2; dielectric layer 2 is cylindrical, made of Si, with a radius of 1200 nm and a thickness of 800 nm; metasurface structural unit 3 is cylindrical, made of ITO, with a radius of... R It is 1200 nm thick. h It is 800 nm. x and y The direction is set as a periodic boundary condition. z The direction is set to perfectly match the boundary conditions, the light source is a plane wave, and the incident direction is... z Negative direction of the axis.

[0053] The reflection spectrum of the device varies with the periodicity of the structural unit arrangement. p Changes such as Figure 5As shown, the amorphous phase exhibits a significant reflection peak in the 6-6.7 μm range, allowing the device to perform filtering within this wavelength range; furthermore, its reflectivity in this range is significantly higher than that of the crystalline phase. However, the reflectivity in the 3-6 μm and 6.7-15 μm wavelength ranges is below 25% and 8% respectively, both exhibiting low reflection responses with a difference of up to 50% from the peak value. Therefore, the device can perform filtering within the 6-6.7 μm wavelength range. (The last sentence appears to be incomplete and possibly refers to a different context.) p As the value increases, the peak reflectance of the amorphous phase gradually increases, and the peak position undergoes a redshift. When the arrangement period... p At a micrometer size of 4.5 μm, the amorphous phase exhibits a reflectivity as high as 75% at ~6.5 μm. Furthermore, when the arrangement period... p When the wavelength is 3.5 μm, the reflectivity of the crystal phase at ~8.8 μm is 39%, at which point the device can filter in the wavelength range of 8-10 μm.

[0054] Example 4:

[0055] A reconfigurable mid-infrared metasurface filter device based on ITO (In₂O₃:SnO₂ = 80:20 wt.%) is constructed. Substrate 1 is made of CaF₂; dielectric layer 2 is cylindrical, made of Si, with a radius of 1200 nm and a thickness of 800 nm; metasurface structural unit 3 is cylindrical, made of ITO, with a radius of... R It is 1200 nm thick. h It is 800 nm. x and y The direction is set as a periodic boundary condition. z The direction is set to perfectly match the boundary conditions, the light source is a plane wave, and the incident direction is... z Negative direction of the axis.

[0056] When the structural unit is an amorphous phase, the device can filter in the wavelength range of 6-7 μm, while when it is a crystalline phase, the device can filter in the wavelength range of 8-10 μm.

[0057] Example 5:

[0058] A reconfigurable mid-infrared metasurface filter device based on ITO (In₂O₃:SnO₂ = 95:5 wt.%) is constructed. Substrate 1 is made of CaF₂; dielectric layer 2 is cylindrical, made of Si, with a radius of 1200 nm and a thickness of 800 nm; metasurface structural unit 3 is cylindrical, made of ITO, with a radius of... R It is 1200 nm thick. h It is 800 nm. x and y The direction is set as a periodic boundary condition. zThe direction is set to perfectly match the boundary conditions, the light source is a plane wave, and the incident direction is... z Negative direction of the axis.

[0059] When the structural unit is an amorphous phase, the device can filter in the wavelength range of 6-7 μm, while when it is a crystalline phase, the device can filter in the wavelength range of 8-10 μm.

Claims

1. A reconfigurable mid-infrared metasurface filter device based on indium tin oxide, characterized in that, The device includes a substrate, on which a dielectric layer and a metasurface structure unit are sequentially disposed; Among them, the metasurface structure unit and the dielectric layer are concentrically arranged to form a basic unit, and the basic unit is periodically arranged on the upper surface of the substrate. The metasurface structural unit material is indium tin oxide, with a composition of (In₂O₃). x (SnO2) y , where 80 wt.%≤x≤95wt.%, 5 wt.%≤y≤20 wt.%, x+y=100; ITO can reversibly switch between amorphous and crystalline phases. When it is in the amorphous phase, the device filters in the wavelength range of 6-7 μm, and when it is in the crystalline phase, the device filters in the wavelength range of 8-10 μm. The substrate is any one of CaF2, Al2O3 and SiO2 materials; The dielectric layer is an optical resonant cavity made of Si, with a cylindrical shape, a thickness of 800 nm, and a radius ranging from 1100 to 1300 nm. The metasurface structure unit has a cylindrical geometry and a thickness of [missing information]. h The range is 600-1000 nm, and the radius is... R Consistent with the dielectric layer, the periodic arrangement period p The range is 3.5-4.5 μm.

2. The reconfigurable mid-infrared metasurface filter device based on indium tin oxide according to claim 1, characterized in that, The overall thickness range of the reconfigurable mid-infrared metasurface filter device is 100-600 μm.

3. The reconfigurable mid-infrared metasurface filter device based on indium tin oxide according to claim 1, characterized in that, In the device, if ITO is an amorphous phase, when h When the wavelength changes from 600 nm to 1000 nm, the filtering wavelength of the device changes from 6.3-6.5 μm to 6.3-7 μm; when R When the wavelength changes from 1100 nm to 1300 nm, the filtering wavelength of the device changes from 6.2-6.5 μm to 6.5-6.9 μm; when p When the wavelength changes from 3.5 μm to 4.5 μm, the filtering wavelength of the device changes from 6-6.4 μm to 6.3-6.7 μm.

4. The reconfigurable mid-infrared metasurface filter device based on indium tin oxide according to claim 1, characterized in that, In the device, if ITO is a crystalline phase, when h When the wavelength changes from 600 nm to 1000 nm, the filtering wavelength of the device changes from 8.5-9 μm to 8.5-10 μm; when R When the wavelength changes from 1100 nm to 1300 nm, the filtering wavelength of the device changes from 8.4-9 μm to 8-10 μm; when p When the wavelength changes from 3.5 μm to 4.5 μm, the filtering wavelength of the device changes from 8-10 μm to 8.8-9.5 μm.

5. A reconfigurable mid-infrared metasurface filter device based on indium tin oxide according to claim 1, characterized in that, The reversible switching between the amorphous phase and the crystalline phase of the metasurface structural unit is achieved by external excitation; the external excitation is a laser pulse or an electrical pulse.

6. A reconfigurable mid-infrared metasurface filter device based on indium tin oxide according to claim 5, characterized in that, During the transition from amorphous to crystalline phase, the temperature of the metasurface structural unit is raised to the crystallization temperature range by applying an external excitation with low to medium energy density and long duration. The external excitation uses a 30-100mW laser pulse or a 0.6-3V electrical pulse.

7. A reconfigurable mid-infrared metasurface filter device based on indium tin oxide according to claim 5, characterized in that, During the transition from crystalline to amorphous phase, by applying a high-energy-density transient external excitation, the local temperature of the metasurface structure unit is raised to above its melting temperature, and rapid cooling is achieved after the excitation is removed, thereby forming an amorphous phase structure. The external excitation uses a 50-150mW laser pulse or a 1.5-5V electrical pulse.

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