An adjustable plane prism

Abstract

This application discloses an adjustable planar prism. It includes, from top to bottom, an electrically conductive structure layer, a dielectric substrate, and a metal backplate. The electrically conductive structure layer includes an insulating layer, on which multiple spaced metasurface basic units are disposed. Each metasurface basic unit includes two graphene strips symmetrically arranged on the upper and lower surfaces of the insulating layer. This adjustable planar prism employs a structure design of a double-layer graphene grating, a dielectric substrate, and a metal backplate, enabling perfect dispersion of the anomalous reflection angle of broadband terahertz waves. Due to the electrically tunable characteristics of graphene, the Fermi level of the graphene in the unit can be changed by applying an external bias voltage, allowing for convenient and rapid dynamic adjustment of the dispersion angle range of the reflected beam. Furthermore, the double-layer electrically biased structure composed of two symmetrically arranged graphene strips facilitates the application of bias voltage and is easy to fabricate.

Description

Technical Field

[0001] This application relates to the field of metasurface technology, specifically to an adjustable planar prism. Background Technology

[0002] In recent years, electromagnetic metasurfaces have attracted widespread attention due to their remarkable ability to manipulate electromagnetic waves. By introducing phase discontinuities at the medium interface, Capasso et al. proposed a generalized Snell's law of reflection and refraction, providing a new degree of freedom for electromagnetic wave beam manipulation using metasurfaces. By designing artificial scatterers on the metasurface and their arrangement, discontinuous gradient phase distributions can be created, allowing arbitrary control of the propagation paths of reflected or refracted waves. This enables anomalous reflection, anomalous refraction, backscatter reduction, angular momentum conversion, helical beamforming, holographic imaging, and digital or coded metasurfaces.

[0003] Since the manipulation of electromagnetic waves by metasurfaces no longer depends on the accumulation of spatial phase, but rather on the phase abrupt change characteristics between superatoms to control the distribution of the spatial phase and radiation angle of electromagnetic waves, this has greatly promoted the development of planarization and miniaturization of devices, and powerfully promoted the theoretical research and engineering application of metasurfaces in higher frequency bands such as terahertz.

[0004] For example, Chinese patent document CN217443570U discloses a nonlinear device for wavefront control based on a graphene nonlinear metasurface. This device includes several periodically distributed metagratings, each comprising a metal substrate with periodically distributed grooves filled with a dielectric layer. The dielectric layer is covered with periodically distributed graphene strips, each with an independent voltage applied to control its chemical potential, thereby achieving a nonlinear phase gradient. However, the inventors recognize that this patent document constructs an electrical bias structure between the upper graphene layer and the substrate by creating grooves and filling the dielectric layer on the metal substrate. This method is difficult to microfabricate. Furthermore, the nonlinear device provided in this prior art mainly controls the beam direction; research on metasurface devices capable of achieving beam dispersion is still lacking. Summary of the Invention

[0005] Therefore, this application provides an adjustable planar prism that can achieve beam dispersion and is easy to manufacture.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] An adjustable planar prism includes an electrical conductor structure layer, a dielectric substrate, and a metal backplate arranged sequentially from top to bottom. The electrical conductor structure layer includes an insulating layer, on which a plurality of metasurface basic units are disposed at intervals. Each metasurface basic unit includes two graphene strips symmetrically arranged on the upper and lower surfaces of the insulating layer. By applying different bias voltages to each metasurface basic unit, the Fermi level of the graphene strips of each metasurface basic unit is adjusted to achieve adjustment of the output beam dispersion angle range of the adjustable planar prism.

[0008] Optionally, eight groups of first metasurface basic unit groups are sequentially arranged on the insulating layer. The Fermi levels of the graphene strips in the eight groups of first metasurface basic unit groups are 0 eV, 0.033 eV, 0.056 eV, 0.112 eV, 0.32 eV, 0.53 eV, 0.69 eV, and 0.85 eV, respectively. Each group of first metasurface basic unit groups includes two or three metasurface basic units.

[0009] Optionally, eight or ten groups of second metasurface basic unit groups are sequentially arranged on the insulating layer, each group of second metasurface basic unit groups including two metasurface basic units with Fermi levels of 0.02eV and 0.43eV for graphene strips.

[0010] Optionally, the spacing between the basic units of the metasurface is 2 micrometers.

[0011] Optionally, the width of the graphene strips is 10 micrometers.

[0012] Optionally, the thickness of the insulating layer is 0.3 micrometers, and the material of the insulating layer is polyvinylidene fluoride terpolymer.

[0013] Optionally, the thickness of the dielectric substrate is 17 micrometers, and the material of the dielectric substrate is a polymer.

[0014] Alternatively, the medium substrate may be made of TOPAS polymer.

[0015] Optionally, the thickness of the metal backplate is 0.2 micrometers, and the material of the metal backplate is gold.

[0016] Compared with the prior art, this application has at least the following beneficial effects:

[0017] This invention provides an adjustable planar prism, which consists of an electrical conductor structure layer, a dielectric substrate, and a metal backplate arranged sequentially from top to bottom. The electrical conductor structure layer includes an insulating layer, on which multiple spaced metasurface basic units are disposed. Each metasurface basic unit includes two graphene strips symmetrically arranged on the upper and lower surfaces of the insulating layer. This adjustable planar prism employs a structure design of a double-layer graphene grating, a dielectric substrate, and a metal backplate, which can achieve perfect dispersion of the anomalous reflection angle of broadband terahertz waves. Due to the electrically tunable characteristics of graphene, the Fermi level of the graphene in the unit can be changed by applying an external bias voltage, allowing the dispersion angle range of the reflected beam to be easily and quickly dynamically adjusted arbitrarily. In addition, the double-layer electrically biased structure composed of two symmetrically arranged graphene strips makes it easier to apply a bias voltage and is easier to manufacture. Attached Figure Description

[0018] To more intuitively illustrate the prior art and this application, several exemplary figures are provided below. It should be understood that the specific shapes and structures shown in the figures should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary figures, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0019] Figure 1 This is a schematic diagram of the structure of an adjustable planar prism provided in an embodiment of this application;

[0020] Figure 2 Another structural schematic diagram of an adjustable planar prism provided for an embodiment of this application;

[0021] Figure 3 This is a partial enlarged view of an adjustable planar prism in an embodiment of this application;

[0022] Figure 4 The reflection phase spectrum and reflection amplitude spectrum of eight graphene microstrips at different Fermi levels;

[0023] Figure 5 A schematic diagram of the simulation results when each type of cell in a single-beam metasurface unit is repeated twice;

[0024] Figure 6 A schematic diagram of the simulation results when each type of cell in a single-beam metasurface unit is repeated three times;

[0025] Figure 7 The reflection phase spectrum and reflection amplitude spectrum of two graphene microstrips at different Fermi levels;

[0026] Figure 8A schematic diagram of the simulation results when each type of cell in the dual-beam metasurface unit is repeated 8 times;

[0027] Figure 9 This is a schematic diagram of the simulation results when each type of cell in the dual-beam metasurface unit is repeated 10 times.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Dielectric substrate; 2. Metal backing plate; 3. Insulating layer; 4. Graphene strip. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] In the description of this application: unless otherwise stated, "a plurality of" means two or more. The terms "first," "second," "third," etc., in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (e.g., they should not be construed as an emphasis on importance or order). Expressions such as "including," "comprising," and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0032] The terms used in this application, such as "upper," "lower," "left," "right," and "middle," are generally used to facilitate intuitive understanding by referring to the accompanying drawings, and are not absolute limitations on the positional relationships in the actual product. Changes in these relative positional relationships, without departing from the technical concept disclosed in this application, should also be considered within the scope of this application.

[0033] In embodiments of the present invention, such as Figure 1 As shown, an adjustable planar prism is provided, comprising an electrical conductor structure layer, a dielectric substrate 1, and a metal backplate 2 arranged sequentially from top to bottom; the electrical conductor structure layer includes an insulating layer 3, on which multiple metasurface basic units are arranged at intervals, each metasurface basic unit including two graphene strips 4 symmetrically arranged on the upper and lower surfaces of the insulating layer 3; by applying different bias voltages to each metasurface basic unit, the Fermi level of the graphene strips 4 of each metasurface basic unit is adjusted, thereby adjusting the range of the outgoing beam dispersion angle of the adjustable planar prism.

[0034] Furthermore, such as Figure 2 As shown, the spacing between the basic units of the metasurface is 2 micrometers. That is, the spacing d between two adjacent graphene strips 4 on the upper and lower surfaces of the insulating layer 3 is 2 micrometers, which means that the spacing between the grating strips of the grating structure composed of graphene strips 4 is 2 micrometers.

[0035] Furthermore, the width w of the graphene strip 4 is 10 micrometers, and the thickness of the graphene strip 4 is approximately 0.34 nanometers.

[0036] Furthermore, the insulation layer 3 has a thickness of 0.3 micrometers and is composed of a polyvinylidene fluoride ternary polymer film with high dielectric strength (dielectric constant 65) to ensure the safety of the device under electrical bias.

[0037] Furthermore, the thickness of the intermediate dielectric substrate 1 is 17 micrometers, and the material of the dielectric substrate 1 is a polymer.

[0038] Preferably, the dielectric substrate 1 is selected to be composed of a TOPAS polymer (refractive index 1.53) with low loss and low dispersion characteristics to achieve better performance. It is an ideal substrate material commonly used in broadband terahertz devices.

[0039] Furthermore, the thickness of the bottom metal backplate 2 (reflective layer) is 0.2 micrometers. The metal backplate 2 is made of gold thin film and is equivalent to a perfect reflective layer in the terahertz band.

[0040] In other words, the adjustable planar prism provided in this embodiment of the invention has a typical three-layer structure, consisting of an electrical conductor structure layer, a dielectric substrate 1, and a metal backplate 2 from top to bottom. The upper electrical conductor structure layer is a grating structure composed of graphene microstrips (i.e., basic metasurface units). To facilitate free control of the graphene conductivity by applying an external voltage, each graphene microstrip is a double-layer electrically biased structure. A partial enlarged view of this adjustable planar prism can be seen in [reference needed]. Figure 3 .

[0041] In the entire structure, each grating period can be considered as the smallest unit of the metasurface (i.e., the basic unit of the metasurface), and the electrical conductivity of the graphene in each basic unit can be independently electrically controlled. Simulations show that when the graphene in the basic unit of the metasurface is at different Fermi levels, its reflection phase spectrum is approximately parallel over a wide frequency band (3.0 THz-3.8 THz).

[0042] like Figure 4 (a) shows the unit reflection phase spectrum of graphene microstrips at different Fermi levels, which allows the phase gradient of the metasurface to be almost dispersionless over a wide frequency band. Simultaneously, it maintains high electromagnetic field reflection efficiency, such as... Figure 4 (b) shows the unit reflection amplitude spectrum of graphene microstrips at different Fermi levels. This provides convenience and possibility for the realization of tunable planar prisms.

[0043] Based on the aforementioned analysis and the reflection characteristics of the basic unit, we can further design an adjustable planar prism function based on a low-dispersion phase gradient metasurface.

[0044] As an optional implementation, a planar triangular prism with single-beam anomalous reflection characteristics was first designed. Eight sets of first metasurface basic unit groups were sequentially arranged on the insulating layer 3 of the adjustable planar triangular prism. The Fermi levels of the graphene strips in the eight sets of first metasurface basic unit groups were 0 eV, 0.033 eV, 0.056 eV, 0.112 eV, 0.32 eV, 0.53 eV, 0.69 eV, and 0.85 eV, respectively. Each set of first metasurface basic unit groups included two or three metasurface basic units with corresponding Fermi levels.

[0045] In other words, this planar prism with anomalous single-beam reflection characteristics is composed of eight basic units of graphene containing different Fermi levels. These units have a 45-degree phase abrupt change, corresponding to Fermi levels of 0 eV, 0.033 eV, 0.056 eV, 0.112 eV, 0.32 eV, 0.53 eV, 0.69 eV, and 0.85 eV. By repeating each type of unit twice side-by-side and arranging them in ascending or descending phase gradient order, the desired single-beam planar prism is formed. Figure 5 (a) shows the results of the full-wave simulation experiment. It can be found that the metasurface produces significant single-beam anomalous reflections at the boundary points and center frequency points (3.0THz, 3.4THz, and 3.8THz) of the frequency band, respectively. Different frequency points correspond to different reflection angles.

[0046] Depend on Figure 5 (b) Further analysis reveals that the anomalous reflection angle of the metasurface gradually decreases with increasing frequency within the 3THz-3.8THz frequency band, perfectly matching the theoretical predictions calculated by the generalized Snell's law, with the main lobe reflection coefficient remaining above 0.64. Furthermore, when the number of repetitions is changed to 3, the dispersion range of the metasurface's anomalous reflection angle can be rapidly switched and adjusted, such as... Figure 6 As shown in (a) and (b).

[0047] As another optional implementation, in order to further verify the effect of the proposed metasurface, a planar triangular prism with dual-beam anomalous reflection characteristics was also designed. The insulating layer 3 of the adjustable planar triangular prism is provided with eight or ten sets of second metasurface basic unit groups. Each set of second metasurface basic unit groups includes two metasurface basic units with Fermi levels of graphene strips of 0.02 eV and 0.43 eV, respectively.

[0048] In other words, this planar prism with dual-beam anomalous reflection characteristics is composed of two basic units of graphene containing different Fermi levels, with a 180-degree phase abrupt change in reflection between the units, corresponding to Fermi levels of 0.02 eV and 0.43 eV, respectively. The reflection phase spectra of the two basic units remain almost parallel in the 3.0 THz to 4.0 THz frequency band, indicating that the reflection phase difference between the units can be maintained around 180 degrees over a wide frequency range, and it also exhibits good electromagnetic field reflection efficiency, such as... Figure 7 As shown in (a) and (b), by repeating each type of unit eight times side-by-side and alternating them according to an increasing or decreasing phase gradient, the desired dual-beam planar prism is formed. Figure 8 (a) shows the full-wave simulation results. It can be seen that the metasurface produces significant symmetrical double-beam anomalous reflections at the boundary points and center frequency points (3.0THz, 3.5THz, and 4.0THz) of the frequency band.

[0049] Depend on Figure 8 (b) It can be seen that the positive and negative anomalous reflection angles of the metasurface gradually decrease with increasing frequency in the 3.0THz-4.0THz frequency band, and this conforms well to the theoretical predictions calculated by the generalized Snell's law, thus realizing the dispersion function of the dual-reflection region. Furthermore, when the number of repetitions of the unit cells is changed to 10, the dual-dispersion range of the metasurface's anomalous reflection angle can be rapidly switched and adjusted, such as... Figure 9 As shown in (a) and (b).

[0050] This invention presents a low-dispersion phase gradient metasurface with electrically tunable characteristics. Its working mode is similar to a reflective planar prism. It can not only simulate a prism to achieve perfect dispersion of the anomalous reflection angle of broadband terahertz waves, but also, due to the electrically tunable characteristics of graphene, change the Fermi level of graphene in the unit by applying an external bias voltage. This allows the dispersion angle range of the anomalous reflection beam of the metasurface to be easily and quickly dynamically adjusted arbitrarily, further enhancing its application potential.

[0051] This invention provides a low-dispersion phase gradient metasurface with electrically tunable characteristics, which can function as a reflective planar prism. Its performance was verified through full-wave simulation, demonstrating that it can not only simulate a prism to achieve perfect dispersion at anomalous reflection angles of broadband terahertz waves, but also realize broadband dispersion of the reflected terahertz wave beam. Due to the introduction of a graphene microstrip structure, the dispersion angle range can be easily and quickly adjusted dynamically. The designed metasurface has broad application potential in wireless communication, optics, imaging, and sensing.

[0052] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

[0053] The present application has been described in a relatively specific and detailed manner above through general descriptions and specific embodiments. It should be understood that, based on the technical concept of the present application, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present application, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the present application.

Claims

1. A planar triangular prism, characterized by, The device comprises, from top to bottom, an electrical conductor structure layer, a dielectric substrate, and a metal backplate; the electrical conductor structure layer includes an insulating layer, on which multiple spaced metasurface basic units are disposed, each metasurface basic unit including two graphene strips symmetrically arranged on the upper and lower surfaces of the insulating layer; by applying a bias voltage to each metasurface basic unit and adjusting the Fermi level of the graphene strip of each metasurface basic unit, the range of emitted beam dispersion angles can be achieved; On the insulating layer, the plurality of spaced metasurface basic units include eight groups of first metasurface basic unit groups arranged sequentially. The Fermi levels of the graphene strips in the eight groups of first metasurface basic unit groups are 0 eV, 0.033 eV, 0.056 eV, 0.112 eV, 0.32 eV, 0.53 eV, 0.69 eV, and 0.85 eV, respectively. There is a 45-degree reflection phase abrupt change between the eight groups of first metasurface basic unit groups. Each group of first metasurface basic unit groups includes two or three metasurface basic units.

2. A planar triangular prism, characterized by The device comprises, from top to bottom, an electrical conductor structure layer, a dielectric substrate, and a metal backplate; the electrical conductor structure layer includes an insulating layer, on which multiple spaced metasurface basic units are disposed, each metasurface basic unit including two graphene strips symmetrically arranged on the upper and lower surfaces of the insulating layer; by applying a bias voltage to each metasurface basic unit and adjusting the Fermi level of the graphene strip of each metasurface basic unit, the range of emitted beam dispersion angles can be achieved; On the insulating layer, the plurality of spaced metasurface basic units include eight or ten groups of second metasurface basic unit groups arranged sequentially. Each group of second metasurface basic unit groups includes two metasurface basic units with Fermi levels of 0.02 eV and 0.43 eV respectively, and the two metasurface basic units have a 180-degree reflection phase abrupt change between them.

3. The planar prism according to claim 2, characterized in that, The spacing between the basic units of the metasurface is 2 micrometers.

4. The planar prism according to claim 2, characterized in that, The width of each graphene strip is 10 micrometers.

5. The planar prism according to claim 2, characterized in that, The insulation layer has a thickness of 0.3 micrometers and is made of polyvinylidene fluoride terpolymer.

6. The planar prism according to claim 2, characterized in that, The thickness of the dielectric substrate is 17 micrometers, and the material of the dielectric substrate is a polymer.

7. The planar prism according to claim 2, characterized in that, The substrate material is TOPAS polymer.

8. The planar prism according to claim 2, characterized in that, The metal backplate has a thickness of 0.2 micrometers and is made of gold.

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