Terahertz modulator based on aluminum and germanium antimony tellurium composite dumbbell hole array

Abstract

The invention discloses a terahertz modulator based on an aluminum and germanium-antimony-tellurium composite dumbbell hole array. The terahertz modulator comprises a substrate and the aluminum and germanium-antimony-tellurium composite dumbbell hole array formed on the surface of the substrate. The aluminum and germanium-antimony-tellurium composite dumbbell hole array is characterized in that a plurality of periodically arranged dumbbell holes are etched in an aluminum thin film, and a layer of germanium-antimony-tellurium thin film covers the aluminum dumbbell hole array; a structural unit of the aluminum dumbbell hole array is composed of two round holes with the same radius and a rectangular hole, the rectangular hole is connected with the two round holes, and the depth of the round holes, the depth of the rectangular hole and the thickness of the aluminum film are the same. The terahertz modulator can dynamically adjust the transmissivity of terahertz waves through germanium-antimony-tellurium phase change. According to the aluminum and germanium-antimony-tellurium composite dumbbell hole array disclosed by the invention, a modulator can be realized in a terahertz frequency band, and dynamic adjustment on the terahertz wave transmissivity is realized by utilizing the phase change characteristic of germanium-antimony-tellurium.

Description

Technical Field

[0001] The invention belongs to the field of terahertz metasurface devices, and in particular relates to a terahertz modulator based on an aluminum and germanium antimony tellurium composite dumbbell hole array. Background Art

[0002] As a device for adjusting the amplitude, phase and polarization of terahertz waves, terahertz modulators are widely used in terahertz communications, imaging, spectroscopy and other fields. Natural materials have limited modulation capabilities for terahertz waves. In recent years, people have conducted extensive research on terahertz metasurfaces, which can arbitrarily design the amplitude, phase and polarization of terahertz waves. Moreover, by combining terahertz metasurfaces with some materials with adjustable refractive index or conductivity, the amplitude, phase or polarization of terahertz waves can be dynamically controlled. Extensively studied materials with adjustable refractive index or conductivity include silicon, graphene, liquid crystal, vanadium dioxide, perovskite, etc. The resonant response of the terahertz metasurface can be adjusted by changing the refractive index or conductivity of these materials through light control, temperature control, electrical control, etc., so that the amplitude, phase or polarization of terahertz waves can be dynamically controlled. Although people have done a lot of research on terahertz modulators, there are still problems such as slow modulation speed and low modulation depth.

[0003] Germanium antimony telluride (Ge2Sb2Te5) has also received a lot of attention in recent years as a phase change material. At room temperature, Ge2Sb2Te5 is in an amorphous phase; when the temperature gradually rises to a certain threshold (usually around 160°C), Ge2Sb2Te5 will transform into a crystalline phase. In addition to temperature, Ge2Sb2Te5 phase change can also be stimulated by current or light pulses. The refractive index and conductivity of Ge2Sb2Te5 change significantly before and after the phase change. Based on the change in the refractive index of Ge2Sb2Te5, many works have combined Ge2Sb2Te5 with metasurfaces to realize dynamically adjustable optical devices. However, most of the previous studies on Ge2Sb2Te5 metasurfaces were conducted in the visible and infrared bands, and there were few studies in the terahertz band. Recently, some works have combined terahertz metasurfaces with Ge2Sb2Te5, and used the Ge2Sb2Te5 phase change to realize dynamic modulation of terahertz waves. However, the modulation depth of terahertz modulators based on Ge2Sb2Te5 metasurfaces is still relatively low. The invention discloses a terahertz modulator based on an aluminum and germanium antimony telluride composite dumbbell hole array, which realizes dynamic adjustment of terahertz wave transmittance through germanium antimony telluride phase change and has a high modulation depth. Summary of the invention

[0004] The present invention proposes a terahertz modulator based on an aluminum and germanium antimony telluride composite dumbbell hole array, which produces a higher transmittance in the terahertz band when the germanium antimony telluride is in an amorphous phase, and a lower transmittance when the germanium antimony telluride is transformed into a crystalline phase, thereby utilizing the germanium antimony telluride phase change to realize dynamic adjustment of the terahertz wave transmittance, and has a higher modulation depth.

[0005] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0006] The invention discloses a terahertz modulator based on an aluminum and germanium antimony telluride composite dumbbell hole array, which is characterized by comprising a substrate and an aluminum and germanium antimony telluride composite dumbbell hole array formed on the surface of the substrate; the aluminum and germanium antimony telluride composite dumbbell hole array is obtained by etching a plurality of dumbbell holes arranged periodically in an aluminum film, and covering the aluminum dumbbell hole array with a layer of germanium antimony telluride film; a structural unit of the aluminum dumbbell hole array is composed of two circular holes with the same radius and a rectangular hole, the rectangular hole connects the two circular holes, and the circular hole depth, the rectangular hole depth and the thickness of the aluminum film are all the same; the terahertz modulator can realize dynamic adjustment of the terahertz wave transmittance through germanium antimony telluride phase change.

[0007] Preferably, the radius of the circular hole in the structural unit of the aluminum and germanium antimony tellurium composite dumbbell hole array is 10-50 μm, and the distance between the centers of two circular holes is 100-200 μm;

[0008] Preferably, the width of the rectangular hole in the structural unit of the aluminum and germanium antimony tellurium composite dumbbell hole array is 5 to 25 μm;

[0009] Preferably, the thickness of aluminum and germanium antimony tellurium in the aluminum and germanium antimony tellurium composite dumbbell hole array is 0.1-0.5 μm;

[0010] Preferably, the aluminum and germanium antimony tellurium composite dumbbell hole array has a lateral period of 200 to 300 μm and a longitudinal period of 100 to 150 μm;

[0011] Preferably, the material of the substrate is any one of polyimide, silicon, quartz and alumina.

[0012] The terahertz modulator based on the aluminum and germanium antimony tellurium composite dumbbell hole array proposed in the present invention can be prepared by the following method: first, a metal aluminum film is deposited on a substrate by magnetron sputtering technology; then, a layer of photoresist is coated on the metal aluminum film by spin coating process, and then the photoresist is etched into the periodically arranged dumbbell hole array by photolithography technology; then, the aluminum film is etched into the periodically arranged dumbbell hole array by wet etching, and then the residual photoresist on the sample surface is removed, thereby obtaining the aluminum dumbbell hole array. Finally, a layer of germanium antimony tellurium film is plated on the aluminum dumbbell hole array by magnetron sputtering technology to obtain the aluminum and germanium antimony tellurium composite dumbbell hole array.

[0013] The terahertz modulator based on the composite dumbbell hole array of aluminum and germanium antimony telluride disclosed in the present invention, wherein when germanium antimony telluride is in an amorphous phase, a ring dipole mode is excited in the composite dumbbell hole array of aluminum and germanium antimony telluride under the incidence of a plane electromagnetic wave, which produces a resonance peak in the transmission spectrum and has a high transmittance. The frequency of the resonance peak can be adjusted by changing the geometric parameters of the structure. When germanium antimony telluride is transformed from an amorphous phase to a crystalline phase, the ring dipole mode is suppressed due to the significant increase in the conductivity of germanium antimony telluride, and the transmittance is also greatly reduced. Therefore, the transmittance of terahertz waves can be dynamically adjusted based on the composite dumbbell hole array of aluminum and germanium antimony telluride, that is, a terahertz modulator is realized.

[0014] The beneficial effects of the present invention are:

[0015] (1) The present invention proposes a design concept for realizing a terahertz modulator using an aluminum and germanium antimony telluride composite dumbbell hole array. When germanium antimony telluride is in an amorphous phase, it produces a higher transmittance in the terahertz band, while when germanium antimony telluride is transformed into a crystalline phase, the transmittance is lower, thereby utilizing the germanium antimony telluride phase change to realize dynamic adjustment of the terahertz wave transmittance.

[0016] (2) Compared with previous terahertz modulators, the present invention has a higher modulation depth, wherein the absolute modulation depth is greater than 0.6 and the relative modulation depth is greater than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : Schematic diagram of aluminum and germanium antimony telluride composite dumbbell hole array in a periodic unit, including germanium antimony telluride layer 1, aluminum layer 2 and substrate layer 3. Among them, r is the radius of the circular hole in the aluminum and germanium antimony telluride composite dumbbell hole array, w is the distance between the centers of the two circular holes, g is the width of the rectangular hole in the dumbbell hole, h1 and h2 are the thicknesses of germanium antimony telluride and aluminum respectively, px is the period along the x direction (transverse period), and py is the period along the y direction (longitudinal period). The polarization direction of the incident electromagnetic wave is along the y direction.

[0018] Figure 2 :(a) is the transmission spectrum of the aluminum and germanium antimony tellurium composite dumbbell hole array in Example 1; (b) is the transmission spectrum of the aluminum and germanium antimony tellurium composite dumbbell hole array in Example 2; (c) is the transmission spectrum of the aluminum and germanium antimony tellurium composite dumbbell hole array in Example 3. Among them, the solid line in the figure is the transmission spectrum when germanium antimony tellurium is in the amorphous phase, and the dotted line in the figure is the transmission spectrum when germanium antimony tellurium is in the crystalline phase. DETAILED DESCRIPTION

[0019] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments.

[0020] Embodiment 1: A terahertz modulator based on a composite dumbbell hole array of aluminum and germanium antimony telluride is disclosed, combined with Figure 1The structure of the aluminum and germanium antimony telluride composite dumbbell hole array within a periodic unit is shown, the radius r of the circular hole in the dumbbell hole is 30μm, the distance w between the centers of the two circular holes is 180μm, the width g of the rectangular hole in the dumbbell hole is 10μm, the thicknesses h1 and h2 of germanium antimony telluride and aluminum are both 0.2μm, the lateral period px is 250μm, the longitudinal period py is 125μm, and the substrate is polyimide.

[0021] When the geometric parameters of the aluminum and germanium antimony telluride composite dumbbell hole array are the above values, the transmission spectrum of germanium antimony telluride in the amorphous phase is as follows: Figure 2 As shown by the solid line in (a), the polarization direction of the incident light is along the y direction. We can see that there is a resonance peak at a frequency of about 0.317 THz, and the transmittance of the resonance peak is 0.76. By calculating the spatial electromagnetic field distribution of the resonance peak frequency, we know that the resonance peak comes from the excitation of the ring dipole mode. We also calculated the transmission spectrum of the structure when GeSbTe is transformed into a crystalline phase, as shown in Figure 2 As shown by the dotted line in (a). At this time, the transmittance at a frequency of 0.317 THz is reduced to 0.001. When GST transforms into a crystalline phase, the ring dipole mode is suppressed due to the significant increase in the conductivity of GST, and the transmittance is greatly reduced. Therefore, the terahertz wave transmittance can be dynamically adjusted by utilizing the GST phase change, thus realizing a terahertz modulator. Under this structural parameter, the absolute modulation depth of the terahertz modulator is 0.759, while the relative modulation depth is 99.87%.

[0022] Example 2: The distance w between the centers of two circular holes in the aluminum and germanium antimony tellurium composite dumbbell hole array in Example 1 is changed to 140 μm, and the other geometric parameters of the structure remain consistent with Example 1, and the substrate is still polyimide.

[0023] When the geometric parameters of the aluminum and germanium antimony telluride composite dumbbell hole array are the above values, the transmission spectrum of germanium antimony telluride in the amorphous phase is as follows: Figure 2 As shown in the solid line in (b), the polarization direction of the incident light is along the y direction. We can see that there is a resonance peak at a frequency of about 0.411 THz, and the transmittance of the resonance peak is 0.71. By calculating the spatial electromagnetic field distribution of the resonance peak frequency, we know that the resonance peak comes from the excitation of the ring dipole mode. We also calculated the transmission spectrum of the structure when GeSbTe is transformed into a crystalline phase, as shown in Figure 2 As shown by the dotted line in (b). At this time, the transmittance at a frequency of 0.411 THz is reduced to 0.001. When GST transforms into a crystalline phase, the ring dipole mode is suppressed due to the significant increase in the conductivity of GST, and the transmittance is greatly reduced. Therefore, the terahertz wave transmittance can be dynamically adjusted by utilizing the GST phase change, thus realizing a terahertz modulator. Under this structural parameter, the absolute modulation depth of the terahertz modulator is 0.709, while the relative modulation depth is 99.86%.

[0024] Example 3: The distance w between the centers of two circular holes in the aluminum and germanium antimony tellurium composite dumbbell hole array in Example 1 is changed to 100 μm, and the other geometric parameters of the structure remain consistent with Example 1, and the substrate is still polyimide.

[0025] When the geometric parameters of the aluminum and germanium antimony telluride composite dumbbell hole array are the above values, the transmission spectrum of germanium antimony telluride in the amorphous phase is as follows: Figure 2 As shown by the solid line in (c), the polarization direction of the incident light is along the y direction. We can see that there is a resonance peak at a frequency of about 0.534 THz, and the transmittance of the resonance peak is 0.64. By calculating the spatial electromagnetic field distribution of the resonance peak frequency, we know that the resonance peak comes from the excitation of the ring dipole mode. We also calculated the transmission spectrum of the structure when GeSbTe is transformed into a crystalline phase, as shown in Figure 2 As shown by the dotted line in (c). At this time, the transmittance at a frequency of 0.534 THz is reduced to 0.002. When GST transforms into a crystalline phase, the ring dipole mode is suppressed due to the significant increase in the conductivity of GST, and the transmittance is greatly reduced. Therefore, the terahertz wave transmittance can be dynamically adjusted by utilizing the GST phase change, thus realizing a terahertz modulator. Under this structural parameter, the absolute modulation depth of the terahertz modulator is 0.638, while the relative modulation depth is 99.69%.

[0026] In summary, the present invention proposes to realize a terahertz modulator using an aluminum and germanium antimony telluride composite dumbbell hole array. When germanium antimony telluride is in an amorphous phase, a higher transmittance is generated in the terahertz band, while when germanium antimony telluride is transformed into a crystalline phase, the transmittance is lower, thereby utilizing the germanium antimony telluride phase change to realize dynamic adjustment of the terahertz wave transmittance, and having a higher modulation depth.

[0027] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A terahertz modulator based on aluminum and germanium antimony telluride composite dumbbell hole array, characterized in that: It includes a substrate and an aluminum and germanium antimony telluride composite dumbbell hole array formed on the surface of the substrate; the aluminum and germanium antimony telluride composite dumbbell hole array is formed by etching a plurality of periodically arranged dumbbell holes in an aluminum film, and covering the aluminum dumbbell hole array with a layer of germanium antimony telluride film; the structural unit of the aluminum dumbbell hole array is composed of two circular holes with the same radius and a rectangular hole, the rectangular hole connects the two circular holes, and the depth of the circular hole, the depth of the rectangular hole and the thickness of the aluminum film are all the same; the terahertz modulator can realize dynamic adjustment of the terahertz wave transmittance through the germanium antimony telluride phase change.

2. The terahertz modulator according to claim 1, characterized in that: The radius of the circular hole in the structural unit of the aluminum and germanium antimony tellurium composite dumbbell hole array is 10-50 μm, and the distance between the centers of two circular holes is 100-200 μm.

3. The terahertz modulator according to claim 1, characterized in that: The width of the rectangular hole in the structural unit of the aluminum and germanium antimony tellurium composite dumbbell hole array is 5 to 25 μm.

4. The terahertz modulator according to claim 1, characterized in that: The thickness of aluminum and germanium antimony tellurium in the aluminum and germanium antimony tellurium composite dumbbell hole array is 0.1-0.5 μm.

5. The terahertz modulator according to claim 1, characterized in that: The aluminum and germanium antimony tellurium composite dumbbell hole array has a lateral period of 200 to 300 μm and a longitudinal period of 100 to 150 μm.

6. The terahertz modulator according to claim 1, characterized in that: The material of the substrate is any one of polyimide, silicon, quartz and alumina.

7. A method, characterized in that The method for preparing a terahertz modulator based on an aluminum and germanium antimony tellurium composite dumbbell hole array according to any one of claims 1 to 6 comprises the following steps: First, a metal aluminum film is deposited on the substrate by magnetron sputtering technology; Then, a layer of photoresist is coated on the metal aluminum film by using a spin coating process, and then the photoresist is etched into the periodically arranged dumbbell hole array by using a photolithography technique; Next, the aluminum film is etched into a periodically arranged dumbbell hole array by wet etching, and then the residual photoresist on the surface of the sample is removed to obtain an aluminum dumbbell hole array. Finally, a layer of germanium antimony telluride thin film is plated on the aluminum dumbbell hole array by using magnetron sputtering technology to obtain the aluminum and germanium antimony telluride composite dumbbell hole array.

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