Guided mode resonance infrared radiation modulator based on GST material

Abstract

The invention discloses a guided-mode resonance type infrared radiation modulator based on a GST material, and belongs to the technical field of optoelectronic devices, the guided-mode resonance type infrared radiation modulator comprises a bottom metal layer, an intermediate medium guided-wave layer and a surface metal layer, the bottom metal layer, the intermediate medium guided-wave layer and the surface metal layer are sequentially deposited from bottom to top, and the bottom metal layer is a Cu substrate; the middle medium wave guide layer comprises a ZnSe medium layer and a GST thin film layer, the GST thin film layer is deposited on the ZnSe medium layer, the ZnSe medium layer is deposited on the Cu substrate, the surface metal layer is an Au grating strip, the Au grating strip is deposited on the GST thin film layer, incident TE polarized light in the y-axis direction is coupled into the waveguide through the top Au grating strip, and the waveguide modes of the ZnSe medium layer and the GST thin film layer are excited. Through the mode, the tuning performance of the infrared radiation device based on the guided-mode resonance grating structure is remarkably improved, and the infrared radiation device has the advantages of being low in power consumption and easy to prepare.

Description

Technical Field

[0001] The invention relates to the technical field of optoelectronic devices, and in particular to a guided mode resonance type infrared radiation modulator based on a GST material. Background Art

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

[0003] Nowadays, precise control of infrared radiation through micro-nano structures can not only effectively improve the freedom of choice of infrared radiation, but also reduce the size of devices and improve integration. The application of infrared radiation devices based on micro-nano structures in the fields of thermophotovoltaics, refrigeration, infrared detection and light sources is becoming increasingly mature. Among them, guided mode resonant grating structure, as an important branch, has made significant research progress in wavelength selective infrared radiation control with its narrow bandwidth and high diffraction efficiency.

[0004] For example, in the prior art, guided mode resonance infrared radiation modulation devices mainly integrate phase change materials such as VO2 (vanadium dioxide) or GST (Ge2Sb2Te5, germanium antimony telluride):

[0005] like Fig. 9 As shown, when VO2 is in an insulating state, the guided mode resonance modes in the dual bands of 3049.9nm and 3604.2nm are excited under TM polarized light, achieving perfect absorption; when vanadium dioxide is in a metallic state, modulation depths of 91% and 81% are achieved in the dual bands respectively. Since VO2 requires continuous energy excitation to maintain the metallic state, such devices generally have the problem of high power consumption.

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

[0007] Based on this, the present invention designs a guided mode resonance type infrared radiation modulator based on GST material to solve the above problems. Summary of the invention

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

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions:

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

[0011] The intermediate dielectric waveguide layer includes a ZnSe dielectric layer and a GST thin film layer, wherein the GST thin film layer is deposited on the ZnSe dielectric layer, and the ZnSe dielectric layer is deposited on the bottom metal layer;

[0012] The ZnSe dielectric layer and the GST thin film layer are the waveguide core;

[0013] The surface metal layer is Au grating strips, which are deposited on top of the GST 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 modes of the ZnSe dielectric layer and the GST thin film layer are excited;

[0015] The GST film layer includes an amorphous state and a crystalline state. The GST film layer is heated at a temperature of a1 degrees Celsius for t1 minutes to be transformed from the amorphous state to the crystalline state.

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

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

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

[0019] Furthermore, 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.

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

[0021] Furthermore, when the GST thin film layer is transformed from an amorphous state to a crystalline state, a high modulation depth of infrared radiation can be achieved.

[0022] Furthermore, the thin films are deposited using electron beam evaporation technology.

[0023] Furthermore, the process of preparing Au grating strips on the GST thin film layer includes contact lithography, electron beam evaporation metal deposition and lift-off process.

[0024] Furthermore, 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 sequentially deposited on the copper film, and after preparation, the thickness of the ZnSe dielectric layer and the GST thin film layer can be measured using an ellipsometer;

[0027] Finally, Au grating strips were fabricated on the GST film by contact lithography, electron beam evaporation metal deposition and lift-off process.

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

[0029] At the same time, the optimization of the dual-waveguide structure design can obtain infrared radiation modulation with a modulation depth of 94% before and after the phase change, which improves the modulation performance. The entire device has a simple structure, consisting only of a thin film and surface metal grating strips, and is easy to prepare.

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

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 This is a structural diagram of a guided mode resonance type infrared radiation modulator based on GST material of the present invention;

[0033] Figure 2 This is a disassembled diagram of a guided mode resonance type infrared radiation modulator based on GST material of the present invention;

[0034] Figure 3 This is a physical picture of a guided mode resonance type infrared radiation modulator based on GST material of the present invention;

[0035] Figure 4 This is a surface morphology diagram of a guided mode resonance type infrared radiation modulator based on GST material of the present invention;

[0036] Figure 5 is the absorption spectrum measured by the present invention under the condition of TE polarized light incident at 15°;

[0037] Figure 6 This is the device electric field distribution diagram at 10.24 μm for the amorphous GST of the present invention;

[0038] Figure 7 This is the device electric field distribution diagram at 10.99 μm for the crystalline GST of the present invention;

[0039] Figure 8 The absorption spectra of the crystallization process of the device of the present invention at different baking times;

[0040] Fig. 9 It is a guided mode resonance type infrared radiation modulation device integrating VO2 in the prior art;

[0041] Fig.10 It is a guided mode resonance type infrared radiation modulation device integrating GST in the prior art. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Embodiment 1: In some embodiments, please refer to the drawings of the specification Figure 1-Figure 8 , a guided mode resonance type infrared radiation modulator based on GST material, comprising a bottom metal layer, an intermediate dielectric waveguide layer and a surface metal layer, wherein the bottom metal layer, the intermediate dielectric waveguide layer and the surface metal layer are deposited in sequence from bottom to top;

[0044] The intermediate dielectric waveguide layer includes a ZnSe dielectric layer and a GST thin film layer, wherein the GST thin film layer is deposited on the ZnSe dielectric layer, and the ZnSe dielectric layer is deposited on 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; other options include an Au substrate, an Al substrate and a Pt substrate. Under the premise of being greater than the skin depth, the above metal substrates can all serve as a perfect reflection layer. Considering the cost issue, the present invention adopts a Cu substrate.

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

[0048] The ZnSe dielectric layer and the GST thin film layer are the waveguide core;

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

[0050] The surface metal layer is Au grating strips, which are deposited on top of the GST 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 modes of the ZnSe dielectric layer and the GST thin film layer are excited;

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

[0053] The GST film layer includes an amorphous state and a crystalline state. The GST film layer is heated at a temperature of a1 degrees Celsius for t1 minutes to transform 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 an amorphous state, there is a strong absorption peak at a wavelength of 10.24 μm, and its absorption intensity is 0.8;

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

[0057] Preferably, all thin films are deposited using electron beam evaporation technology.

[0058] Preferably, the process of preparing Au grating strips on the GST thin film layer includes contact photolithography, electron beam evaporation metal deposition and lift-off process.

[0059] The infrared radiance modulator designed in the present invention is fabricated using standard thin film deposition and photolithography techniques.

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

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

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

[0063] Finally, Au grating strips were fabricated on the GST film by contact lithography, electron beam evaporation metal deposition and lift-off process.

[0064] The present invention is based on a metal-medium-metal MIM structure. Considering the characteristic that the guided mode resonance effect is sensitive to the refractive index of the surrounding medium, GST material and ZnSe dielectric material are introduced into the intermediate dielectric waveguide layer. The waveguide mode is mainly distributed in a double-layer waveguide composed of a ZnSe dielectric layer and a GST thin film layer. The GST thin film layer is phase-changed from an amorphous state to a crystalline state by applying thermal excitation. The GST thin film layer is phase-changed from an amorphous state to a crystalline state by applying thermal excitation. The crystallization process first forms crystal nuclei quickly and over a large range. Then, the crystal nuclei grow within a limited distance and merge with other grown crystal nuclei to form crystals in an orderly arrangement. The crystal has a non-volatile phase change characteristic. After the GST phase change, the state can be kept stable for a long time without the need for continuous energy excitation. Therefore, the crystal has the advantage of low power consumption.

[0065] At the same time, the optimization of the dual-waveguide structure design can obtain infrared radiation modulation with a modulation depth of 94% before and after the phase change, which improves the modulation performance. The entire device has a simple structure, consisting only of a thin film and surface metal grating strips, and is easy to prepare.

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

[0067] Embodiment 2: In some embodiments, Figure 3 and Figure 4 As shown, as a preferred embodiment of the present invention, Figure 3 An optical microscope image of the fabricated infrared radiation modulator is shown, with an area size of 1 cm × 1 cm.

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

[0069] Embodiment 3: In some embodiments, Figure 5 , Figure 6 and Figure 7 As shown, as a preferred embodiment of the present invention, Figure 5As shown in Figure 2, when the GST film layer is in an amorphous state, there is a strong absorption peak at a wavelength of 10.24 μm, and its absorbance is 0.8; the corresponding electric field distribution is shown in Figure 2. Figure 6 As shown, these electric fields are 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, that is, there is no electric field component in the transmission direction, but there is a magnetic field component) mode.

[0070] The infrared radiation modulator was placed on a hot plate at 140°C and heated for 10 minutes to make the GST film layer crystalline. After the phase change of the GST film layer, the wavelength shifted to 10.99 μm, the line width became wider, and the absorption intensity dropped to 0.26. The electric field distribution is shown in the figure below. Figure 7 As shown, the electric field distribution of this resonance is similar to that of the mode at 10.24 μm, but the field intensity is significantly reduced.

[0071] Due to the non-volatile tuning characteristics of the GST thin film layer, the infrared radiation modulator can maintain a long-term stable state after heating, so it has lower power consumption.

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

[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 in previous literature.

[0075]

[0076] Embodiment 4: In some embodiments, Figure 8 As shown in FIG. 1 , as a preferred embodiment of the present invention, as the baking time gradually increases to 10 minutes, the guided mode resonance absorption peak gradually moves from 10.24 μm to 10.99 μm. Its 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 the amplitude can be achieved by controlling the heating time.

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

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such 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 invention.

Claims

1. A guided mode resonance infrared radiation modulator based on GST material, characterized in that: It includes a bottom metal layer, an intermediate dielectric waveguide layer and a surface metal layer, and the bottom metal layer, the intermediate dielectric waveguide layer and the surface metal layer are deposited in sequence from bottom to top; The intermediate dielectric waveguide layer includes a ZnSe dielectric layer and a GST thin film layer, wherein the GST thin film layer is deposited on the ZnSe dielectric layer, and the ZnSe dielectric layer is deposited on the bottom metal layer; The ZnSe dielectric layer and the GST thin film layer are the waveguide core; The surface metal layer is Au grating strips, which are deposited on top of the GST film layer; The GST film layer includes an amorphous state and a crystalline state. The GST film layer is heated at a temperature of a1 degrees Celsius for t1 minutes to transform from the amorphous state to the crystalline state. 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 modes of the ZnSe dielectric layer and the GST thin film layer are excited.

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

3. The guided mode resonance type infrared radiation modulator based on GST material according to claim 2 is characterized in that: The bottom metal layer adopts a Cu substrate, an Au substrate, an Al substrate or a Pt substrate.

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

5. The guided mode resonance infrared radiation modulator based on GST material according to claim 1, characterized in that: 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 guided mode resonance infrared radiation modulator based on GST material according to claim 1, characterized in that: a1 is 130-150; t1 is 5-15.

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

8. The guided mode resonance infrared radiation modulator based on GST material according to claim 3 or 4, characterized in that: The thin films were deposited using electron beam evaporation technology.

9. The guided mode resonance infrared radiation modulator based on GST material according to claim 5, characterized in that: The process of preparing Au grating strips on the GST thin film layer includes contact lithography, electron beam evaporation metal deposition and lift-off process.

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