Terahertz metal grating coupler optical switch

Abstract

A switch body comprises a metal substrate, a glass dielectric layer, a graphene regulation and control layer and a metal grating layer which are sequentially arranged from bottom to top, and the metal grating layer comprises a plurality of grating units which are sequentially arranged in the direction of a first output end OUT1 and a second output end OUT2 at intervals. Each grating unit comprises a first grating convex edge, a second grating convex edge and a third grating convex edge which are sequentially arranged at intervals, and the widths of the first grating convex edge, the second grating convex edge and the third grating convex edge are sequentially increased. The graphene layer is used as an impedance regulation and control module, the state of the graphene layer is regulated by using the Fermi level of graphene, and the grating structure is matched with the graphene layer, so that the terahertz coupler optical switch is enabled to switch on or off the function of converting a free propagation wave (PW) into a surface wave (SW) by controlling the Fermi level of the graphene.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz metal grating coupling, and particularly to a terahertz metal grating coupler optical switch. Background Art

[0002] Terahertz waves generally refer to electromagnetic waves with frequencies mainly in the range of 0.1 - 10 THz (1 THz = 10^12 Hz), located between microwaves and infrared rays in the electromagnetic spectrum. Due to the unique properties of terahertz waves such as short wavelength, good directivity, low photon energy, and high penetrability, terahertz technology has important academic value and broad application prospects in multiple fields such as communication, radar, security inspection imaging, biomedicine, and spectrum analysis. The excitation of terahertz waves is generated by dipole oscillations driven by coherent currents or by coherent laser pulses through nonlinear optical difference frequency, with high temporal and spatial coherence.

[0003] Existing terahertz time-domain spectroscopy technology can directly measure the amplitude and phase of the oscillating electromagnetic field, which has great advantages in studying the transient coherent dynamics of materials. In the terahertz band, most metals can still be regarded as good conductors, but the loss is already higher than that in the microwave band. Terahertz radiation generation technology and terahertz waveguide technology are the most critical core technologies in terahertz technology, and terahertz sources and waveguide devices are also the most critical components in terahertz systems.

[0004] Terahertz band couplers are generally designed as five-branch structures to ensure a certain bandwidth. However, due to the high frequency and short wavelength, the width dimension of each waveguide branch is very small, making it difficult to manufacture due to processing technology limitations. In the low-frequency band (such as the terahertz or microwave band), the dielectric constant of metal is extremely large, resulting in an extremely small skin depth of electromagnetic waves, usually much smaller than the wavelength order of magnitude. Thus, metal is approximately an ideal conductor. Under ideal conditions, the conductivity of metal can be regarded as infinite, leading to no significant electromagnetic field distribution inside the metal. In addition, the absorption loss of metal to electromagnetic waves can be ignored. Therefore, transmission lines based on this property are applicable not only to longer wavelengths (such as meter waves) but also to shorter wavelengths (such as millimeter waves), and may even be extended to the terahertz band. Due to the small transverse size of surface wave transmission lines, they have extensive value in practical applications. However, rectangular and circular metal tube terahertz waveguides, parallel metal plate terahertz waveguides, sapphire single crystal terahertz waveguides, and plastic plate terahertz waveguides generally have a common problem: almost all materials exhibit a high absorption rate in the terahertz band, resulting in large transmission losses for these waveguides. For the practical application of terahertz waveguides, achieving low-loss transmission is a key problem to be solved urgently. Research shows that when using metal wires and sub-wavelength plastic optical fibers for terahertz wave transmission, the loss can be significantly reduced, even approaching zero loss. Since most of the energy propagates in the air, its confinement and anti-interference capabilities are poor. Planar dielectric waveguides can operate in the fundamental mode and play a crucial role in millimeter waves and terahertz waves. Compared with metal plate waveguides, planar dielectric waveguides can more effectively concentrate electromagnetic energy in the internal dielectric region for transmission, thus significantly enhancing the energy aggregation ability of the waveguide. Dielectric waveguides belong to a semi-open surface wave guide structure, and the electromagnetic wave radiation loss at their bends and discontinuities is relatively large, which poses a challenge to practical applications. Summary of the Invention

[0005] To solve the technical problems existing in the background art, the present invention proposes a terahertz metal grating coupler optical switch.

[0006] A terahertz metal grating coupler optical switch proposed by the present invention includes a switch body. The switch body includes a metal substrate, a glass dielectric layer, a graphene regulation layer, and a metal grating layer arranged in sequence from bottom to top. One side of the metal grating layer of the switch body has an input end IN, and the opposite ends of the switch body respectively have a first output end OUT1 and a second output end OUT2.

[0007] The metal grating layer includes a plurality of grating units arranged at intervals in sequence from the directions of the first output terminal OUT1 and the second output terminal OUT2. Each grating unit includes a first grating ridge, a second grating ridge, and a third grating ridge arranged at intervals in sequence from the directions of the first output terminal OUT1 and the second output terminal OUT2. The widths of the first grating ridge, the second grating ridge, and the third grating ridge increase in sequence.

[0008] The thickness of the metal substrate layer is greater than the skin depth of the electromagnetic wave.

[0009] The free-propagating wave conversion surface wave switch is adjusted by controlling the Fermi level of the graphene regulation layer.

[0010] Preferably, the metal grating layer includes 3 - 5 grating units.

[0011] Preferably, the metal grating layer includes 4 grating units.

[0012] Preferably, the center distance between the first grating ridge and the second grating ridge is equal to the center distance between the second grating ridge and the third grating ridge.

[0013] Preferably, the glass dielectric layer is made of TOPAS material.

[0014] Preferably, the metal substrate is made of aluminum material.

[0015] Preferably, the metal grating layer is made of aluminum material.

[0016] Preferably, the first grating ridge, the second grating ridge, and the third grating ridge have equal lengths.

[0017] In the present invention, for the terahertz metal grating coupler optical switch proposed, the switch body includes a metal substrate, a glass dielectric layer, a graphene regulation layer, and a metal grating layer arranged in sequence from bottom to top. The metal grating layer includes a plurality of grating units arranged at intervals in sequence from the directions of the first output terminal OUT1 and the second output terminal OUT2. Each grating unit includes a first grating ridge, a second grating ridge, and a third grating ridge arranged at intervals in sequence. The widths of the first grating ridge, the second grating ridge, and the third grating ridge increase in sequence. By using the graphene layer as an impedance regulation module, the state of graphene is adjusted by using its Fermi level, and the grating structure cooperates with the graphene layer. By controlling the Fermi level of graphene, the terahertz coupler optical switch turns on or off the function of converting the free-propagating wave (PW) into the surface wave (SW). Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of an embodiment of a terahertz metal grating coupler optical switch proposed by the present invention.

[0019] Figure 2Schematic diagram of the optical path of an embodiment of a terahertz metal grating coupler optical switch proposed by the present invention. Specific implementation mode

[0020] As Figure 1 and 2 shown, Figure 1 Schematic diagram of the structure of an embodiment of a terahertz metal grating coupler optical switch proposed by the present invention, Figure 2 Schematic diagram of the optical path of an embodiment of a terahertz metal grating coupler optical switch proposed by the present invention.

[0021] Referring to Figure 1 , a terahertz metal grating coupler optical switch proposed by the present invention, a terahertz metal grating coupler optical switch, characterized in that it includes a switch body, and the switch body includes a metal substrate 1, a glass dielectric layer 2, a graphene regulation layer 3, and a metal grating layer 4 arranged in sequence from bottom to top. One side of the metal grating layer 4 of the switch body has an input end IN, and the opposite ends of the switch body respectively have a first output end OUT1 and a second output end OUT2;

[0022] The metal grating layer 4 includes a plurality of grating units arranged at intervals in sequence from the directions of the first output end OUT1 and the second output end OUT2. Each grating unit includes a first grating ridge 41, a second grating ridge 42, and a third grating ridge 43 arranged at intervals in sequence from the directions of the first output end OUT1 and the second output end OUT2. The widths of the first grating ridge 41, the second grating ridge 42, and the third grating ridge 43 increase in sequence;

[0023] The thickness of the metal substrate 1 layer is greater than the skin depth of the electromagnetic wave;

[0024] The free-propagating wave to surface wave switch is adjusted by controlling the Fermi level of the graphene regulation layer 3.

[0025] In the specific working process of the terahertz metal grating coupler optical switch of this embodiment, referring to Figure 2 , the first output end OUT1 and the second output end OUT2 are respectively arranged at the opposite ends of the optical switch, and the power is obtained by integrating the power density of the two output ends respectively. The power magnitudes of the left and right side ports are compared to reflect the directional transmission performance of the coupler. When the graphene is at 0 eV, the graphene undergoes a phase change, and the function of converting the free-propagating wave (PW) into a surface wave (SW) of the terahertz coupler optical switch is turned on. When the graphene is at 1 eV, the function of converting the free-propagating wave (PW) into a surface wave (SW) of the terahertz coupler optical switch based on the two-dimensional graphene material is turned off.

[0026] In a specific embodiment, the switch body includes, from top to bottom, a top metal grating layer 4, a graphene layer 3, a dielectric layer 2, and a metal substrate 1 in sequence.

[0027] Among them, the metal grating layer 4 is made of metal aluminum material, with a thickness of 1.9 um, and is a unit structure composed of three to five groups of the same grating structures. Among them, the gratings from right to left in one group of the unit structure are the first grating ridge 41, the second grating ridge 42, and the third grating ridge 43 respectively. The lengths of the three are the same, all 363.6 um, and the widths are 3.2 um, 20 um, and 25 um respectively. In the specific design method of the grating, the center distance between the first grating ridge 41 and the second grating ridge 42 is equal to the center distance between the second grating ridge 42 and the third grating ridge 43, both being 30.3 um.

[0028] The metal grating layer 4 is attached to the upper surface of the graphene layer 3, the lower surface of the graphene layer 3 is attached to the upper surface of the dielectric layer 2, and the metal substrate 1 is attached to the lower surface of the dielectric layer 2. After the four-layer structure of the switch body is combined, a square periodic unit is formed, and its planar contour in the top view is square, with a side length of the square being 363.6 um.

[0029] The graphene layer 3 is two-dimensional material graphene.

[0030] The dielectric layer 2 is made of TOPAS (Thermoplastic Olefin Polymer of Amorphous Structure) material, which is a cycloolefin copolymer (COC) produced by the German company TOPAS Advanced Polymers. The thickness of the dielectric layer 2 is 9.7 um, and the refractive index is 1.53.

[0031] The material of the metal substrate 1 is metal aluminum, with a thickness of 0.2 um and a conductivity of σ = 3.56×10 7 S / m.

[0032] In this embodiment, as Figure 2 shown, the second output end OUT2 of the optical switch is arranged opposite to the first output end OUT1. The power density of the second output end OUT2 and the first output end OUT1 are integrated respectively to obtain their powers, and the power sizes of the two output ends are compared to reflect the directional transmission performance of the coupler.

[0033] When the Fermi level of graphene is 0 eV, when terahertz light is vertically incident from the top input end IN, after the optical field is regulated by the phase gradient of the metal grating, the power of the second output end can reach -3.14436*10-12 W, while the power of the first output end is 2.56463*10 -13 W. It can be seen from the data that the energy of the vertical incidence is fromFigure 2 Output occurs on the right side, so the function of converting free-propagating waves to surface waves of its optical switch is turned on.

[0034] When the Fermi level of graphene is 1 eV, when terahertz light is perpendicularly incident from the top input terminal IN, the power at the second output terminal is -1.48353×10 -12 W, while the power at the first output terminal is -2.61036×10 -12 W. It can be seen from the data that almost no energy of the perpendicular incidence exits from the two side output terminals. Therefore, the function of converting free-propagating waves to surface waves of its optical switch is turned off.

[0035] It can be seen from the simulation results in Table 1 that when the metal grating layer 4 includes 4 grating units. When the Fermi level of graphene is 0 eV, it is in the open state, and the directional transmission performance of converting free-propagating waves to surface waves is the best.

[0036] Table 1 Simulation of Terahertz Output Power

[0037]

[0038] As mentioned above, only the preferred specific embodiments of the present invention are described, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A terahertz metal grating coupler optical switch, characterized in that: The switch body comprises a switch body, the switch body comprising a metal substrate (1), a glass dielectric layer (2), a graphene control layer (3) and a metal grating layer (4) arranged in sequence from bottom to top, the metal grating layer (4) of the switch body having an input terminal IN on one side, and the switch body having a first output terminal OUT1 and a second output terminal OUT2 at two opposite ends respectively; The metal grating layer (4) comprises a plurality of grating units arranged in sequence from the first output end OUT1 and the second output end OUT2, each grating unit comprises a first grating ridge (41), a second grating ridge (42) and a third grating ridge (43) arranged in sequence from the first output end OUT1 and the second output end OUT2, and the widths of the first grating ridge (41), the second grating ridge (42) and the third grating ridge (43) increase in sequence; The thickness of the metal substrate (1) layer is greater than the skin depth of the electromagnetic wave; The free propagation wave conversion surface wave switch is regulated by controlling the Fermi level of the graphene control layer (3).

2. The terahertz metal grating coupler optical switch according to claim 1, characterized in that: The metal grating layer (4) includes 3-5 grating units.

3. The terahertz metal grating coupler optical switch according to claim 2, characterized in that: The metal grating layer (4) includes four grating units.

4. The terahertz metal grating coupler optical switch according to claim 1, characterized in that: The center distance between the first grating ridge (41) and the second grating ridge (42) is equal to the center distance between the second grating ridge (42) and the third grating ridge (43).

5. The terahertz metal grating coupler optical switch according to any one of claims 1 to 3, characterized in that: The glass dielectric layer (2) is made of TOPAS material.

6. The terahertz metal grating coupler optical switch according to any one of claims 1 to 3, characterized in that: The metal substrate (1) is made of aluminum material.

7. The terahertz metal grating coupler optical switch according to any one of claims 1 to 3, characterized in that: The metal grating layer (4) is made of aluminum material.

8. The terahertz metal grating coupler optical switch according to claim 1, characterized in that: The lengths of the first grating ridge (41), the second grating ridge (42) and the third grating ridge (43) are equal.

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