Gst-based terahertz unit and terahertz device

Abstract

The utility model relates to a kind of terahertz unit and terahertz device based on GST, including setting metal structure layer on silicon substrate layer;Wherein, metal structure layer is metal film, and elliptical via array is opened on metal film;Elliptical via array of metal structure layer constitutes two groups of active unit group and a group of passive unit group, and active unit group is covered GST film, and passive unit group is not covered GST film.Terahertz device based on GST of the terahertz unit, the terahertz device includes multiple as described previously terahertz unit;Active unit group U1 and passive unit group U3 are arranged in interval alternately in same column, and active unit group U2 is a column alone, and two columns are arranged adjacent;GST super surface is the matrix of adjacent arrangement repeating alternately arranged;The silicon substrate layer of adjacent terahertz unit is in abutment alignment arrangement;The utility model based on GST terahertz device structure is simple, and small in size, and preparation process is simple.

Description

Technical Field

[0001] This application belongs to the field of terahertz metasurface technology, specifically relating to a terahertz unit and terahertz device based on GST. Background Technology

[0002] Terahertz (THz) waves lie between microwaves and far-infrared bands, with wavelengths ranging from 0.03 mm to 3 mm and corresponding frequencies from 0.1 THz to 10 THz. Due to the unique characteristics of this wavelength range, terahertz waves exhibit enormous application potential in fields such as astronomy, communications, biomedicine, and security inspection. Terahertz metasurfaces, as ultrathin metamaterials composed of function-driven artificial superatomic arrays, offer a crucial technological pathway to realizing lightweight, compact photonic devices.

[0003] In terahertz units, metallic structural layers can achieve abrupt modulation of the phase and amplitude of electromagnetic waves, realizing efficient electromagnetic wave phase and amplitude control. Existing metallic structural layers mostly employ C-shaped slit structures; see [link to relevant documentation]. Figure 1 As shown, although this type of structure can achieve certain functions, the design of the C-shaped slit structure is relatively complex. It usually requires changing multiple parameters such as size and opening size to achieve phase change. The process is complex and discontinuous, and the processing accuracy requirements are high, which is not conducive to the fabrication and promotion of the device.

[0004] Germanium-antimony-tellurium (GST), a typical chalcogenide phase transition material, can repeatedly switch between two states by applying external stimuli (light, heat, or electrical stimulation), and the amorphous and crystalline states of GST exhibit significant differences in optical and electrical properties. However, in relevant technologies, there is no mention of the integrated application of GST for terahertz units and devices, nor is there any integration method to combine GST with terahertz units or devices to optimize performance or achieve specific functions. Summary of the Invention

[0005] To address the problems of existing technologies, this invention proposes a terahertz unit and terahertz device based on GST; the specific technical solution is as follows:

[0006] A terahertz unit based on GST, the terahertz unit comprising: a metal structure layer disposed on a silicon substrate; wherein the metal structure layer is a metal thin film, and elliptical vias are formed on the metal thin film; the elliptical vias of the metal structure layer constitute active units and passive units, the active units are covered with a GST film, and the passive units are not covered with a GST film.

[0007] The terahertz unit based on GST has an elliptical through-hole with a rotation angle of θ. θ is based on the x-axis and is the angle at which the elliptical through-hole rotates around its center. θ can be any angle within the range of 0 to π. The x-axis is a horizontal reference axis.

[0008] The GST film has a different thickness than the silicon substrate.

[0009] A terahertz device based on GST terahertz units, the terahertz device comprising multiple terahertz units as described above; the multiple terahertz units constitute two groups of active units and one group of passive units, the active unit group U1 and the passive unit group U3 are arranged alternately in the same column, the active unit group U2 is in a separate column, and the two columns are arranged adjacently; the GST metasurface is a matrix of adjacent alternating arrangements; the silicon substrates of adjacent terahertz units are aligned and abutted; the multiple terahertz units are arranged in at least 60 rows and 60 columns sequentially.

[0010] In a terahertz unit terahertz device, the center points of the metal structure layer and the silicon substrate layer coincide.

[0011] Terahertz devices, specifically active and passive unit groups, are obtained by arranging elliptical metal vias with different rotation directions in rows and columns, with the rotation angle determined by the phase distribution.

[0012] The specific explanation is as follows:

[0013] A GST-based terahertz unit, the terahertz unit comprising:

[0014] A metal structure layer is used to achieve abrupt modulation of the phase and amplitude of the transmitted wave, thereby realizing efficient electromagnetic wave phase and amplitude control functions; wherein, the metal structure layer is a metal thin film, and the metal thin film has an array of elliptical through holes.

[0015] A GST film based on an elliptical array of through-holes in a metal structure layer is used to cover one side of the metal structure layer; wherein, the GST film is amorphous and the terahertz unit has high transmittance; or the GST film is crystalline and the terahertz unit has low transmittance.

[0016] The center points of the metal structure layer and the silicon substrate layer coincide.

[0017] Preferably, the material of the metal structural layer is aluminum.

[0018] Preferably, the rotation angle of the metal structure layer is θ, which is based on the x-axis and is the angle of rotation of the elliptical through hole around the center. θ can be any angle within the range of 0 to π; the x-axis is a horizontal reference axis.

[0019] Preferably, the conductivity of the GST film in the crystalline state is different from that in the amorphous state.

[0020] Preferably, the GST film has a different thickness than the silicon substrate.

[0021] Secondly, this application also provides a GST-based terahertz device, which includes a plurality of terahertz units as described above.

[0022] The terahertz units are arranged in rows and columns, with the silicon substrates of adjacent terahertz units aligned and abutting each other; the terahertz units are arranged in at least 60 rows and 60 columns.

[0023] Multiple terahertz units as described above constitute active unit groups and passive unit groups. The difference between active unit groups and passive unit groups is that active unit groups are covered with GST films, while passive unit groups are not covered with GST films.

[0024] The device includes two groups of active units and one group of passive units, a passive unit group U3 for implementing the required function, an active unit group U2 for implementing another required function, and an active unit group U1 for canceling the passive unit group.

[0025] The active unit group U1 and the passive unit group U3 are arranged alternately in the same column; the active unit group U2 forms a separate column, and the two columns are arranged adjacent to each other.

[0026] Preferably, the GST-based terahertz device includes: two groups of active units and one group of passive units; the active unit group U1 and the passive unit group U3 are arranged alternately in the same column; the active unit group U2 forms a separate column, and the two columns are arranged adjacent to each other; the specific active unit group and the passive unit group are obtained by arranging metal elliptical through holes with different rotation directions in rows and columns, and the rotation angle is determined by the phase distribution.

[0027] The phase distribution of the active unit group U1 is determined by equation (1);

[0028] (1)

[0029] The phase distribution of the active unit group U2 is determined by equation (2);

[0030] (2)

[0031] The phase distribution of the passive unit group U3 is determined by equation (3);

[0032] (3)

[0033] Where λ is the wavelength in free space, l1 is the topological charge of the focusing vortex generator, and f x , f y , f z Let be the focal point of the metalens, y be the coordinate on the y-axis, and x be the coordinate on the x-axis. The phase distribution of the active unit group U1, The phase distribution of the active unit group U2, To determine the phase distribution of the active unit group U3, U1 introduces a π phase delay relative to U3 at the focal plane, resulting in destructive interference between U1 and U3. U2 is designed with a focal length f. z = 3 mm, x-direction offset f x The metasurface has a thickness of 6 mm, and U3 acts as a focusing vortex generator with a topological charge of l1 = 1. When GST is in the amorphous state, the metasurface functions as a metalens; when GST is in the crystalline state, the metasurface functions as a focusing vortex generator.

[0034] This application has the following technical advantages:

[0035] This application provides a GST-based terahertz unit and terahertz device. The terahertz unit includes a metal structure layer and a bottom silicon substrate layer arranged sequentially. The metal structure layer has elliptical vias, which are simple in structure and easy to fabricate. By simply rotating the elliptical vias, a geometric phase can be introduced, easily achieving continuous phase coverage from 0 to 2π. The GST film is a phase change material, and its conductivity can be controlled by temperature, thereby controlling the performance of the entire terahertz unit. The GST-based terahertz device is composed of multiple GST-based terahertz units arranged together, enabling dual functionality: a metalens function in the amorphous state of GST and a focusing vortex generator function in the crystalline state of GST. The GST-based terahertz device has a simple structure, small size, and simple fabrication process. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a conventional terahertz unit and terahertz device in which the metal structure layer often adopts a C-shaped through-hole structure, as provided in the embodiments of this application.

[0037] Figure 2 This is a schematic diagram of a terahertz unit based on GST provided in an embodiment of this application;

[0038] Figure 3 A schematic diagram of the simulated amplitude and phase distribution of eight terahertz units without integrated GST at a frequency of 0.75THz, provided for an embodiment of this application;

[0039] Figure 4The present application provides a simulated amplitude and phase distribution of eight integrated GST terahertz units based on crystalline and amorphous GST at a frequency of 0.75 THz.

[0040] Figure 5 A schematic diagram of a GST-based terahertz device provided in this application embodiment;

[0041] Figure 6 A schematic diagram of simulation results for a GST-based terahertz device provided for an embodiment of this application;

[0042] Figure 7 A schematic diagram illustrating the experimental characterization results of a GST-based terahertz device provided in this application embodiment;

[0043] Wherein: 1-terahertz unit; 11-GST film; 12-metal structure layer; 121-elliptical via; 13-silicon substrate layer. Detailed Implementation

[0044] Please see Figures 2-7 This application provides a terahertz unit 1 based on GST, including a metal structure layer 12 and a silicon substrate layer 13 arranged sequentially from top to bottom.

[0045] The metal structure layer 12 is the core functional unit for the precise control of electromagnetic waves on the metasurface, and its role is to interact strongly with the incident wave. By refining the design of the size, geometry and spatial arrangement of the metal structure, the key parameters (phase and amplitude) of the transmitted wave can be modulated abruptly, thereby achieving efficient electromagnetic wave phase and amplitude control functions; wherein, the material of the metal structure layer 12 is aluminum.

[0046] The rotation angle of the metal structure layer 12 is θ, which is based on the x-axis (the horizontal reference axis). θ is the angle at which the elliptical through hole 121 rotates around the center. The rotation angle θ is any angle in the range of 0 to π. The silicon substrate layer 13 is disposed on the lower surface of the metal structure layer 12.

[0047] Among them, the elliptical through-hole 121 is the basic unit formed by machining on the metasurface. It has an overall asymmetrical elliptical hollow shape, and its core structural features are as follows: The main body is the elliptical through-hole 121 formed on the metal thin film. Geometric dimensions: including a minor axis length of 60~80μm and a major axis length of 90~110μm. The elliptical through-hole 121 in the metal structural layer constitute active and passive units. The active units are covered with a GST film 11, while the passive units are not covered with a GST film 11.

[0048] In one feasible implementation, the dimensions of the elliptical via 121 in the metal structure layer 12 are: the minor axis of the ellipse is 60~80μm and the major axis of the ellipse is 90~110μm; the dimensions of the square in the silicon substrate layer 13 are: the period is 100~120μm.

[0049] The thickness of the GST film 11 is 100~200nm; the thickness of the metal structure layer 12 is 100~300nm; and the thickness of the bottom silicon substrate layer 13 is 550~700μm.

[0050] In other embodiments of this application, a GST-based terahertz device is also provided, the device comprising a plurality of GST-based terahertz units 1 provided in this invention. The plurality of GST-based terahertz units 1 are arranged in rows and columns in sequence, and the bottom silicon substrate 13 of adjacent GST-based terahertz units 1 are aligned and abutted against each other.

[0051] The GST-based terahertz device comprises a metal structure layer 12 and a bottom silicon substrate layer 13, arranged sequentially from top to bottom. The thickness of the bottom silicon substrate layer 13 is 550–700 μm; the thickness of the metal structure layer 12 is 100–300 nm; and the thickness of the GST film 11 is 100–200 nm. At room temperature, the GST is amorphous and has a conductivity of approximately σ = 8.9 × 10⁻⁶. 2 When the temperature reaches 340℃, GST is in a crystalline state with a conductivity of approximately σ = 1.0 × 10⁻⁶ m / s. 5 S / m. Room temperature usually refers to standard room temperature, which is generally defined as 20℃ to 25℃, with a common value of: room temperature ≈ 25℃.

[0052] Preferably, the GST-based terahertz device includes: two groups of active units and one group of passive units; the active unit group U1 and the passive unit group U3 are arranged alternately in the same column; the active unit group U2 forms a separate column, and the two columns are arranged adjacent to each other; the specific active unit group and the passive unit group are obtained by arranging metal elliptical through holes 121 with different rotation directions in rows and columns, and the rotation angle is determined by the phase distribution.

[0053] The phase distribution of the active unit group U1 is determined by equation (1);

[0054] (1)

[0055] The phase distribution of the active unit group U2 is determined by equation (2);

[0056] (2)

[0057] The phase distribution of the passive unit group U3 is determined by equation (3);

[0058] (3)

[0059] Where λ is the wavelength in free space, l1 is the topological charge of the focusing vortex generator, and f x , f y , f z Let be the focal point of the metalens, y be the coordinate on the y-axis, and x be the coordinate on the x-axis. The phase distribution of the active unit group U1, The phase distribution of the active unit group U2, The phase distribution of active unit group U3 is shown. U1 introduces a π phase delay relative to U3 at the focal plane, resulting in destructive interference between U1 and U3. U2 is designed with a focal length f. z = 3 mm, x-direction offset f x = 6mm superlens, while U3, as a focusing vortex generator, has a topological charge of l1 = 1.

[0060] Terahertz devices based on GST have a simple structure and are easy to integrate, achieving the following effects: realizing the function of a metalens in the amorphous state of GST; realizing the function of a focusing vortex generator in the crystalline state of GST.

[0061] This application presents a novel terahertz unit 1 that combines GST phase transition characteristics with an elliptical through-hole metal structure, achieving multifunctionality of the device while ensuring structural simplicity and feasible fabrication process.

[0062] It should be noted that, Figure 3 The simulated amplitude and phase distribution of eight terahertz units 1 without GST integration at a frequency of 0.75 THz shows a phase jump of about π / 4 with almost the same amplitude.

[0063] Figure 6 The simulation results are for this GST-based terahertz device. Among them, Figure 6 (a) shows a schematic diagram of a metasurface. Figure 6 (b) Partial optical microscope image of the metasurface, and magnified view of the basic unit. Figure 6 (c) Simulated normalized intensity distribution in the amorphous state of GST and Figure 6 (d) Phase distribution. Figure 6 (e) Simulated normalized intensity distribution of GST in crystalline state and Figure 6 (f) Phase distribution.

[0064] Figure 7 The experimental characterization results of this GST-based terahertz device are shown. The normalized intensity distribution in the x–y plane was measured at 2–4 mm above the sample under four different conditions. Figure 7(a) Amorphous state, Figure 7 (b) Crystalline state, Figure 7 (c) Re-amorphous state and Figure 7 (d) Recrystallized state. Figure 7 (e) along Figure 7 (a) and Figure 7 (b) Normalized terahertz intensity curve extracted from the focal position of the superconducting lens. Figure 7 (f) Phase distribution of a focused optical vortex generator in the crystalline state. Figure 7 (g) along Figure 7 (c) and Figure 7 (d) Normalized terahertz intensity curve extracted from the focal position of the superconducting lens. Figure 7 (h) Phase distribution of a focused optical vortex generator in the recrystallized state.

[0065] In other embodiments of this application, a schematic diagram of a terahertz unit structure based on GST is provided, see [link to relevant documentation]. Figure 2 As shown. The GST-based terahertz unit 1 includes a metal structure layer 12 arranged vertically and a bottom silicon substrate layer 13.

[0066] The bottom silicon substrate 13 is square with a period of 100~120μm and a thickness of 550~700μm.

[0067] Among them, the metal structure layer 12 is an elliptical through hole 121 with a minor axis of 60~80μm, a major axis of 90~110μm, a rotation angle of θ, a thickness of 100~300nm, and the material is aluminum.

[0068] Among them, GST film 11 has a thickness of 100~200 nm; GST is amorphous at room temperature and has an electrical conductivity of approximately σ = 8.9 × 10⁻⁶. 2 When the temperature reaches 340℃, GST is in a crystalline state with a conductivity of approximately σ = 1.0 × 10⁻⁶ m / s. 5 S / m.

[0069] For the GST-based terahertz unit 1 in this embodiment, this invention performed numerical simulations on the terahertz unit 1 without integrated GST. When a right-hand circularly polarized wave is incident perpendicularly, for every π / 8 increase in the unit rotation angle θ, the cross-polarized transmission phase undergoes a π / 4 jump while maintaining amplitude stability. Finally, at a frequency of 0.75 THz, eight terahertz units 1 with almost identical transmission amplitudes and a phase spacing of approximately π / 4 were selected to achieve 2π phase coverage. See [link to relevant documentation]. Figure 3 As shown.

[0070] Furthermore, numerical simulations were performed on the terahertz unit 1 integrated with GST. At a frequency of 0.75 THz, the transmittance of the GST-based terahertz unit 1 in amorphous and crystalline states were 0.43 and 0.03, respectively. (See [link to relevant documentation]). Figure 4 As shown.

[0071] In other embodiments of this application, a GST-based terahertz device is provided. The GST-based terahertz device is formed by arranging multiple GST-based terahertz units 1 provided in the present invention. Specifically, the multiple GST-based terahertz units 1 are arranged in rows and columns, and the bottom silicon substrate layers 13 of adjacent GST-based terahertz units 1 are aligned and abutted against each other.

[0072] Specifically, the number of GST-based terahertz units 1 and the number of rows and columns are determined according to the specific application; the GST-based terahertz units are arranged in at least 60 rows and 60 columns.

[0073] In this embodiment, the GST-based terahertz device is formed by arranging multiple GST-based terahertz units 1 in a periodic manner. See [link to documentation]. Figure 5 As shown.

[0074] For the GST-based terahertz device of this embodiment, numerical simulation was performed. Specifically, at room temperature, GST is amorphous, and the GST-based terahertz device functions as a metalens. As the temperature increases, GST undergoes a phase transition, transforming into a crystalline state, and the GST-based terahertz device functions as a focusing vortex generator. (See [link to relevant documentation]). Figure 6 As shown.

[0075] Regarding the GST-based terahertz device of this embodiment, this utility model has fabricated the GST-based terahertz device of this embodiment and performed experimental characterization using a near-field scanning terahertz microscope (NSTM) system.

[0076] This invention was experimentally characterized using a near-field scanning terahertz microscope (NSTM) system. The intensity normalization test results under right-handed circularly polarized wave incidence are shown below. Figure 7 As shown in (a)–(d) in the figure. See also the phase distribution of the two-focused optical vortex generators. Figure 7As shown in (f) and (h) in the figure. When the GST is amorphous (after fabrication), the GST-based terahertz device functions as a metalens, focusing at (6mm, 0mm, 3mm), enabling optical focusing with large distance offset. When the GST is crystalline (annealing temperature increased to 280℃), the GST-based terahertz device functions as a focusing optical vortex generator, with a donut-shaped annular intensity distribution and a spiral phase distribution with a 2π phase shift. Furthermore, when the GST is re-amorphous (nanosecond laser irradiation), the device functions as a metalens. When the GST is recrystallized (annealing temperature increased to 280℃ again), the device functions as a focusing optical vortex generator.

[0077] Regarding the GST-based terahertz device in this embodiment, it should be noted that, due to the local heating effect induced by the metal structure and the thermal confinement effect, the GST in the GST-based terahertz device can crystallize at about 280°C, which is lower than the phase transition temperature of pure GST.

[0078] For the GST-based terahertz device in this embodiment, this invention extracts the normalized intensity distribution at the focal point of the metalens, which exhibits obvious focusing characteristics. See [link to relevant documentation]. Figure 7 As shown in (e) and (g) in the diagram.

Claims

1. A terahertz unit based on GST, characterized in that, The terahertz unit includes: a metal structure layer disposed on a silicon substrate; wherein the metal structure layer is a metal thin film, and elliptical through holes are formed on the metal thin film; the elliptical through holes of the metal structure layer constitute active units and passive units, the active units are covered with a GST film, and the passive units are not covered with a GST film.

2. The terahertz unit based on GST as described in claim 1, characterized in that, The rotation angle of the elliptical through hole is θ, which is based on the x-axis and is the angle of rotation of the elliptical through hole around the center. θ is any angle in the range of 0 to π; the x-axis is the horizontal reference axis.

3. The terahertz unit based on GST as described in claim 1, characterized in that, The GST film has a different thickness than the silicon substrate.

4. A terahertz device based on GST terahertz units, characterized in that, The terahertz device includes a plurality of terahertz units as described in any one of claims 1 to 3; the plurality of terahertz units constitute two groups of active units and one group of passive units, the active unit group U1 and the passive unit group U3 are arranged alternately in the same column, the active unit group U2 is in a separate column, and the two columns are arranged adjacently; the GST metasurface is a matrix of adjacent alternating arrangements; the silicon substrates of adjacent terahertz units are aligned and abutted; the plurality of terahertz units are arranged in at least 60 rows and 60 columns in sequence.

5. The terahertz device based on GST terahertz units as described in claim 4, characterized in that, The center points of the metal structure layer and the silicon substrate layer coincide.

6. The terahertz device based on the GST terahertz unit as described in claim 4, characterized in that, The specific active and passive unit groups are obtained by arranging metal elliptical through holes of different rotation directions in rows and columns, and the rotation angle is determined by the phase distribution.

7. The terahertz device based on GST terahertz units as described in claim 6, characterized in that, The phase distribution is as follows: The phase distribution of the active unit group U1 is determined by equation (1); （1） The phase distribution of the active unit group U2 is determined by equation (2); （2） The phase distribution of the passive unit group U3 is determined by equation (3); （3） Where λ is the wavelength in free space, l1 is the topological charge of the focusing vortex generator, and f x , f y , f z Let be the focal point of the metalens, y be the coordinate on the y-axis, and x be the coordinate on the x-axis. The phase distribution of the active unit group U1, The phase distribution of the active unit group U2, The phase distribution of the active unit group U3 is given by the topological charge number l1 = 1.

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