A guided-mode resonance infrared radiation modulator based on GST material

Abstract

The application discloses a kind of based on GST material's guided mode resonance class infrared radiation modulator, belong to the technical field of optoelectronic devices, including bottom metal layer, intermediate dielectric waveguide layer and surface metal layer, bottom metal layer, intermediate dielectric waveguide layer and surface metal layer are deposited from bottom to top in turn, the bottom metal layer is Cu substrate;Intermediate dielectric waveguide layer includes ZnSe dielectric layer and GST film layer, GST film layer is deposited above ZnSe dielectric layer, ZnSe dielectric layer is deposited above Cu substrate, surface metal layer is Au grating strip, Au grating strip is deposited above GST film layer, by top Au grating strip, the incident TE polarized light along y axis direction is coupled into waveguide, so that the waveguide mode of ZnSe dielectric layer and GST film layer is excited.By the above mode, the tuning performance of the infrared radiation device based on guided mode resonance grating structure is significantly improved, and has the advantages of low power consumption and easy to prepare.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optoelectronic devices, in particular to a guided-mode resonance infrared radiation modulator based on GST material. BACKGROUND

[0002] Thermal radiation refers to the phenomenon that an object radiates electromagnetic waves outward due to its own temperature, which usually occurs in the infrared band and is also called infrared radiation. The atmospheric window is mainly concentrated in the 3-5 μm and 8-13 μm bands. By manipulating the infrared radiation in these bands, technologies such as stealth, thermal insulation, and refrigeration can be achieved.

[0003] Nowadays, precise control of infrared radiation through micro-nano structures not only effectively improves the selection freedom of infrared radiation, but also reduces the size of devices and improves the integration. Infrared radiation devices based on micro-nano structures are increasingly mature in applications such as thermophotovoltaics, refrigeration, infrared detection, and light sources. As an important branch, guided-mode resonance grating structures have made significant research progress in wavelength-selective infrared radiation control due to their narrow bandwidth and high diffraction efficiency.

[0004] For example, existing guided-mode resonance infrared radiation modulation devices mainly integrate phase change materials such as VO2 (vanadium dioxide) or GST (Ge2Sb2Te5, germanium antimony tellurium):

[0005] As shown in Figure 9 , when VO2 is in an insulating state, TM polarized light excites a double-band guided-mode resonance mode at 3049.9 nm and 3604.2 nm, achieving perfect absorption. When vanadium dioxide is in a metallic state, it achieves a modulation depth of 91% and 81% in the respective double bands. Since VO2 requires continuous energy excitation to maintain the metallic state, this type of device generally has high power consumption.

[0006] As shown in Figure 10 , GST is integrated into a sinusoidal grating waveguide. After GST phase change, the resonance peak is significantly broadened due to material loss, with an amplitude modulation depth of only about 48%. At the same time, the preparation of a sinusoidal grating is difficult, so the existing guided-mode resonance infrared radiation devices integrated with GST have low modulation capability and are difficult to prepare.

[0007] Based on this, the present application designs a guided-mode resonance infrared radiation modulator based on GST material to solve the above problems. SUMMARY

[0008] In view of the above shortcomings of the prior art, the present application provides a guided-mode resonance infrared radiation modulator based on GST material.

[0009] To achieve the above purpose, the present application is realized by the following technical scheme:

[0010] A guided-mode resonance infrared radiation modulator based on GST material, comprising a bottom metal layer, an intermediate medium waveguide layer and a surface metal layer, the bottom metal layer, the intermediate medium waveguide layer and the surface metal layer are sequentially deposited from bottom to top;

[0011] The intermediate medium waveguide layer comprises a ZnSe medium layer and a GST thin film layer, the GST thin film layer is deposited above the ZnSe medium layer, and the ZnSe medium layer is deposited above the bottom metal layer;

[0012] The ZnSe medium layer and the GST thin film layer are waveguide cores;

[0013] The surface metal layer is an Au grating strip, and the Au grating strip is deposited above the GST thin film layer;

[0014] The incident TE polarized light along the y-axis direction is coupled into the waveguide through the top Au grating strip, so that the waveguide mode of the ZnSe medium layer and the GST thin film layer is excited;

[0015] The GST thin film layer comprises amorphous and crystalline states, and the GST thin film layer is heated at a1 degrees Celsius for t1 minutes to convert from the amorphous state to the crystalline state.

[0016] Further, the thickness of the bottom metal layer is 100-300nm.

[0017] Further, the bottom metal layer adopts Cu substrate, Au substrate, Al substrate or Pt substrate.

[0018] Further, the thickness d3 of the ZnSe medium layer is 1.8-2μm, and the thickness d2 of the GST thin film layer is 0.25-0.35μm.

[0019] Further, the thickness d1 of the Au grating strip is 0.05-0.15μm, the period p of the Au grating strip is 7.5-8.5μm, and the width w of the surface Au strip is 4.5-4.9μm.

[0020] Further, a1 is 130-150; t1 is 5-15.

[0021] Further, the GST thin film layer can achieve high modulation depth of infrared radiation when it is converted from the amorphous state to the crystalline state.

[0022] Further, the deposition of the thin film adopts electron beam evaporation technology.

[0023] Further, the process for preparing the Au grating strip on the GST thin film layer comprises contact lithography, electron beam evaporation deposition of metal and stripping process.

[0024] Further, the preparation method of the infrared radiation modulator is:

[0025] First, a copper film is deposited on a silicon wafer to form a Cu substrate;

[0026] Next, a ZnSe dielectric layer and a GST thin film layer are deposited on the copper film in sequence, and the thickness of the ZnSe dielectric layer and the GST thin film layer can be measured by an ellipsometer after preparation;

[0027] Finally, an Au grating bar is prepared on the GST thin film through contact lithography, electron beam evaporation deposition of metal and stripping process.

[0028] Compared with the prior art, the present application has the following advantages: the present application is based on a MIM structure of metal-dielectric-metal, and the GST material and the ZnSe dielectric material are introduced into the intermediate dielectric waveguide layer considering the characteristic that the guided mode resonance effect is sensitive to the refractive index of the surrounding medium. The waveguide mode is mainly distributed in the double-layer waveguide composed of the ZnSe dielectric layer and the GST thin film layer. By applying a thermal excitation, the GST thin film layer is changed from an amorphous state to a crystalline state. The crystallization process first forms crystal nuclei rapidly and in a large range, and then the crystal nuclei grow within a limited distance and merge with other growing crystal nuclei to form crystals in an orderly arrangement. The GST has a non-volatile phase change characteristic, and the state of the GST after phase change can remain stable for a long time without the need for continuous energy excitation. Therefore, the present application has the advantage of low power consumption.

[0029] Meanwhile, the optimization of the double-waveguide structure design can obtain an infrared radiation modulation with a modulation depth of 94% before and after phase change, which improves the modulation performance. The entire device structure is simple and only consists of a thin film and a surface metal grating bar, which is easy to prepare.

[0030] The technical scheme of the present application significantly improves the tuning performance of the infrared radiation device based on the guided mode resonance grating structure, and has the advantages of low power consumption and easy preparation. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any creative labor.

[0032] Figure 1 A structure diagram of a guided mode resonance type infrared radiation modulator based on GST material according to the present application;

[0033] Figure 2 A split diagram of a guided mode resonance type infrared radiation modulator based on GST material according to the present application;

[0034] Figure 3 A surface topography diagram of a guided-mode resonance infrared radiation modulator based on GST material according to the present application;

[0035] Figure 4 A surface topography diagram of a guided-mode resonance infrared radiation modulator based on GST material according to the present application;

[0036] Figure 5 An absorption spectrum measured in the case of TE polarized light 15° incidence according to the present application;

[0037] Figure 6 A device electric field distribution diagram at 10.24 μm when the amorphous GST according to the present application;

[0038] Figure 7 A device electric field distribution diagram at 10.99 μm when the crystalline GST according to the present application;

[0039] Figure 8 An absorption spectrum of a crystallization process of the device according to the present application under different baking times;

[0040] Figure 9 A guided-mode resonance infrared radiation modulator device integrating VO2 in the prior art;

[0041] Figure 10 A guided-mode resonance infrared radiation modulator device integrating GST in the prior art. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0043] Embodiment one: in some embodiments, referring to the drawings of the specification Figures 1-8 A guided-mode resonance infrared radiation modulator based on GST material, comprising a bottom metal layer, an intermediate dielectric waveguide layer and a surface metal layer, the bottom metal layer, the intermediate dielectric waveguide layer and the surface metal layer are sequentially deposited from bottom to top;

[0044] The intermediate dielectric waveguide layer comprises a ZnSe dielectric layer and a GST thin film layer, the GST thin film layer is deposited above the ZnSe dielectric layer, and the ZnSe dielectric layer is deposited above the bottom metal layer;

[0045] Preferably, the thickness of the bottom metal layer is 200 nm.

[0046] Preferably, the bottom metal layer is a Cu substrate; alternatively, an Au substrate, an Al substrate and a Pt substrate can also be used, all of which can be used as perfect reflection layers when the depth is greater than the skin depth; considering the cost, the Cu substrate is used in the application.

[0047] Preferably, the Cu substrate comprises a silicon wafer and a copper film deposited on the silicon wafer.

[0048] The ZnSe dielectric layer and the GST thin film layer are waveguide cores.

[0049] Preferably, the thickness of the ZnSe dielectric layer d3 is 1.9 μm, and the thickness of the GST thin film layer d2 is 0.3 μm.

[0050] The surface metal layer is an Au grating strip deposited on the GST thin film layer.

[0051] The incident TE polarized light along the y-axis direction is coupled into the waveguide through the top Au grating strip, so that the waveguide mode of the ZnSe dielectric layer and the GST thin film layer is excited.

[0052] Preferably, the thickness of the Au grating strip d1 is 0.1 μm, the period of the Au grating strip p is 8 μm, and the width of the surface Au strip w is 4.7 μm.

[0053] The GST thin film layer comprises amorphous and crystalline states, and the GST thin film layer is heated at a1 degrees Celsius for t1 minutes to change from the amorphous state to the crystalline state.

[0054] Preferably, a1 is 140, and t1 is 10.

[0055] Preferably, when the GST thin film layer is in the amorphous state, there is a strong absorption peak at a wavelength of 10.24 μm, and the absorption intensity is 0.8.

[0056] When the GST thin film layer is in the crystalline state, there is a strong absorption peak at a wavelength of 10.99 μm, and the absorption intensity is 0.26, and the absorption at 10.24 μm becomes 0.05, achieving a modulation depth of 94%.

[0057] Preferably, all the thin film deposition is performed by using an electron beam evaporation technique.

[0058] Preferably, the process for preparing the Au grating strip on the GST thin film layer comprises contact lithography, electron beam evaporation deposition of metal and stripping process.

[0059] The infrared emissivity modulator designed in the application is made of standard thin film deposition and lithography technology.

[0060] The preparation method of the infrared emissivity modulator is as follows:

[0061] First, a copper film is deposited on a silicon wafer to form a Cu substrate;

[0062] Next, a ZnSe dielectric layer and a GST thin film layer are deposited on the copper film in sequence, and the thickness of the ZnSe dielectric layer and the GST thin film layer can be measured by an ellipsometer after preparation;

[0063] Finally, an Au grating bar is prepared on the GST thin film through contact lithography, electron beam evaporation deposition of metal and stripping process.

[0064] The present application is based on a MIM structure of metal-dielectric-metal, and the GST material and ZnSe dielectric material are introduced into the intermediate dielectric waveguide layer considering the characteristic that the guided mode resonance effect is sensitive to the refractive index of the surrounding medium. The waveguide mode is mainly distributed in the double-layer waveguide composed of the ZnSe dielectric layer and the GST thin film layer. The GST thin film layer is changed from amorphous state to crystalline state by applying thermal excitation. The crystallization process is first to form crystal nucleus rapidly and in a large range, and then the crystal nucleus grows in a limited distance and merges with other growing crystal nucleus to form crystal in an orderly arrangement. The GST has the characteristic of non-volatile phase change, and can keep the state stable for a long time after phase change without continuous energy excitation, so it has the advantage of low power consumption.

[0065] Meanwhile, the optimization of the double waveguide structure design can obtain an infrared radiation modulation with a modulation depth of 94% before and after phase change, which improves the modulation performance. The whole device structure is simple and only composed of thin film and surface metal grating bar, which is easy to prepare.

[0066] The technical scheme of the present application significantly improves the tuning performance of the infrared radiation device based on the guided mode resonance grating structure, and has the advantages of low power consumption and easy preparation.

[0067] In some embodiments, as shown in Figure 3 and Figure 4 , as a preferred embodiment of the present application, Figure 3 the optical microscope image of the prepared infrared radiation modulator is shown, and the area size is 1 cm x 1 cm.

[0068] The scanning electron microscope (SEM) image of the top view of the infrared radiation modulator is shown in Figure 4 , and the size of the surface Au grating is close to the designed value, with a deviation of less than 5%.

[0069] In some embodiments, as shown in Figure 5 , Figure 6 and Figure 7 , as a preferred embodiment of the present application, as shown in Figure 5As shown, when the GST thin film layer is in amorphous state, there is a strong absorption peak at wavelength of 10.24 μm, with an absorption of 0.8; the corresponding electric field distribution is as shown in FIG. 2B. Figure 6 As shown, the electric field is confined in the ZnSe dielectric layer and the GST thin film layer, indicating that it is a TE waveguide (all electric field components are perpendicular to the transmission direction, i.e. there is no electric field component in the transmission direction, but there is a magnetic field component) mode.

[0070] After the GST thin film layer is heated for 10 minutes on a hot plate at 140 °C to become crystalline, the wavelength is shifted to 10.99 μm, the line width is widened, and the absorption intensity is reduced to 0.26, and the electric field distribution is as shown in FIG. 2D. Figure 7 As shown, the resonant electric field distribution is similar to that at 10.24 μm, but the field strength is significantly reduced.

[0071] Due to the non-volatile tuning characteristics of the GST thin film layer, the infrared radiation modulator after heating can maintain the state for a long time, thus having lower power consumption.

[0072] Therefore, the resonant absorption peak excited by the guided mode resonance has a red shift of X μm (the absorption peak moves to the long wave direction, the wavelength becomes longer, and the frequency is reduced) when the GST thin film layer changes from amorphous state to crystalline state;

[0073] X = 10.99 - 10.24 = 0.75

[0074] At 10.24 μm, the modulation depth of absorption reaches Y%, which is twice the modulation depth of the previous literature.

[0075]

[0076] In some embodiments, as shown in FIG. 3A, the guided mode resonance absorption peak gradually shifts from 10.24 μm to 10.99 μm as the baking time gradually increases to 10 min, as a preferred embodiment of the present application. Figure 8 As shown, the guided mode resonance absorption peak gradually shifts from 10.24 μm to 10.99 μm as the baking time gradually increases to 10 min, as a preferred embodiment of the present application. The peak absorption also decreases from 0.8 to 0.26. The intermediate state of GST has different amorphous and crystalline fractions, and continuous modulation of amplitude can be achieved by controlling the heating time.

[0077] In the above embodiment, the phase change material of the GST thin film layer is integrated in the guided mode resonance infrared radiation modulation device, which can provide a low-power modulation method. Based on the optimization of the structure, a modulation depth of 94% is achieved in the mid-infrared band, with excellent modulation performance. The entire device structure is simple, easy to prepare and integrate, and provides a technical method for the practical development of infrared radiation modulation devices.

[0078] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A guided-mode resonance based infrared radiation modulator of the Fabry-Perot type, based on a GST material, characterized in that: The bottom metal layer, the intermediate medium waveguide layer and the surface metal layer are sequentially deposited from bottom to top; The intermediate medium waveguide layer comprises a ZnSe medium layer and a GST thin film layer, the GST thin film layer is deposited above the ZnSe medium layer, and the ZnSe medium layer is deposited above the bottom metal layer; The ZnSe medium layer and the GST thin film layer are waveguide cores; The surface metal layer is an Au grating strip, and the Au grating strip is deposited above the GST thin film layer; The GST thin film layer is a phase change material layer, and the GST thin film layer is heated at a1 degrees Celsius for t1 minutes to transform from an amorphous state to a crystalline state; TE polarized light along the y-axis direction is coupled into the waveguide through the top Au grating strip, the y-axis direction is parallel to the length direction of the grating strip, so that the waveguide mode of the ZnSe medium layer and the GST thin film layer is excited.

2. The GST material based guided mode resonance infrared radiation modulator according to claim 1, wherein, The thickness of the bottom metal layer is 100-300 nm.

3. The GST material based guided mode resonance infrared radiation modulator according to claim 2, wherein, The bottom metal layer adopts a Cu substrate, an Au substrate, an Al substrate or a Pt substrate.

4. The GST material based guided mode resonance infrared radiation modulator according to claim 1, wherein, The thickness d3 of the ZnSe medium layer is 1.8-2 μm, and the thickness d2 of the GST thin film layer is 0.25-0.35 μm.

5. The GST material based guided mode resonance infrared radiation modulator according to claim 1, wherein, The thickness d1 of the Au grating strip is 0.05-0.15 μm, the period p of the Au grating strip is 7.5-8.5 μm, and the width w of the surface Au strip is 4.5-4.9 μm.

6. The GST material based guided mode resonance infrared radiation modulator according to claim 1, wherein, a1 is 130-150; t1 is 5-15.

7. The GST material based guided mode resonance infrared radiation modulator according to claim 1 or 4, wherein, After the GST thin film layer transforms from an amorphous state to a crystalline state, high modulation depth of infrared radiation can be achieved.

8. The GST material based guided mode resonance infrared radiation modulator according to claim 3 or 4, wherein, The deposition of the thin film adopts an electron beam evaporation technology.

9. The GST material based guided mode resonance infrared radiation modulator according to claim 5, wherein, The process of preparing the Au grating strip on the GST thin film layer comprises contact lithography, electron beam evaporation deposition of metal and stripping process.

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