Terahertz photoconductive antenna with metasurface coupling structure

Abstract

The invention provides a terahertz photoconductive antenna with a metasurface coupling structure, which can be applied to the technical field of terahertz transmitting antennae, and comprises a photoconductive antenna which generates a photoconductive effect through optical pumping excitation so as to radiate terahertz waves; and the metasurface unit is integrated in the radiation area of the photoconductive antenna and is used for regulating and controlling the phase, the amplitude and the polarization of the terahertz waves. By integrating the metasurface and the terahertz photoconductive antenna, efficient, high-directivity and tunable terahertz radiation is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz emission antennas, and more particularly to a terahertz photoconductive antenna with a metasurface coupling structure. Background Art

[0002] The terahertz band (0.1 - 10 THz) has important application prospects in the fields of communication, imaging, sensing, and biomedicine. As an efficient terahertz radiation source, the terahertz photoconductive antenna can generate broadband terahertz pulses through the photoconductive effect, but its radiation efficiency and directivity are usually limited by the antenna structure. Traditional terahertz photoconductive antennas have the following problems: (1) low radiation efficiency, the radiation efficiency of photoconductive antennas is usually low, especially in the high-frequency band, where the energy loss is large; (2) poor directivity, the radiation directivity of traditional antennas is relatively wide, and it is difficult to achieve highly directional terahertz radiation; (3) limited tuning ability, the radiation frequency and directivity of traditional antennas are difficult to adjust flexibly, and it is difficult to meet diverse application scenarios; (4) large size, the structure of traditional antennas is complex, and it is difficult to achieve miniaturization and integration.

[0003] To solve the above problems, various solutions have been proposed. Traditional terahertz antennas use traditional antenna structures (such as horn antennas and dipole antennas), but it is difficult to achieve high directivity and tuning ability; photonic crystal structures can achieve the regulation of terahertz waves through photonic crystals, but their structures are complex and it is difficult to achieve high-efficiency radiation; liquid crystal tuning technology can achieve the tuning of terahertz waves through liquid crystal materials, but the tuning speed is slow and the loss is large. None of them have achieved significant effects.

[0004] Metasurface is a two-dimensional artificial electromagnetic structure that can regulate electromagnetic waves at the sub-wavelength scale and exhibits unique electromagnetic properties. Combining the terahertz photoconductive antenna with the metasurface is expected to break through the performance bottleneck of traditional antennas and achieve high-efficiency, highly directional, and tunable terahertz radiation. Summary of the Invention

[0005] (I) Technical Problems to be Solved

[0006] In view of the above problems, the present invention provides a terahertz photoconductive antenna with a metasurface coupling structure. By designing special metasurface units and integrating them with the photoconductive antenna, high-efficiency, highly directional, and tunable terahertz radiation is achieved.

[0007] (II) Technical Solutions

[0008] In view of the above technical problems, an embodiment of the present invention proposes a terahertz photoconductive antenna with a metasurface coupling structure.

[0009] According to the first aspect of the present invention, a terahertz photoconductive antenna with a metasurface coupling structure is provided, including: a photoconductive antenna that generates a photoconductive effect through optical pumping excitation to radiate terahertz waves; and a metasurface unit integrated in the radiation region of the photoconductive antenna for regulating the phase, amplitude, and polarization of terahertz waves.

[0010] In some exemplary embodiments, the photoconductive antenna includes two symmetric interdigital electrodes, and a photoconductive material is disposed between the two interdigital electrodes.

[0011] In some exemplary embodiments, the metasurface unit is composed of periodically arranged sub-wavelength structure units.

[0012] In some exemplary embodiments, the photoconductive material includes low-doped gallium arsenide or indium gallium arsenide.

[0013] In some exemplary embodiments, the sub-wavelength structure unit includes one of a metal nanostructure or a dielectric metasurface unit.

[0014] In some exemplary embodiments, the metal nanostructure includes one of a nanoantenna or a nanohole; and the dielectric metasurface unit includes a high-refractive-index dielectric nanocolumn.

[0015] In some exemplary embodiments, the metasurface unit regulates the phase and amplitude of terahertz waves through the sub-wavelength structure unit to achieve highly directional radiation.

[0016] In some exemplary embodiments, by changing the structural parameters of the metasurface unit or applying an external electric field or magnetic field, dynamic tuning of the terahertz radiation frequency and directivity is achieved.

[0017] In some exemplary embodiments, the structural parameters of the metasurface unit include the period, unit shape, and size.

[0018] In some exemplary embodiments, the size of the sub-wavelength structure unit is smaller than the wavelength of terahertz waves.

[0019] (III) Beneficial Effects

[0020] As can be seen from the above technical solutions, a terahertz photoconductive antenna with a metasurface coupling structure provided by the embodiments of the present invention has at least the following beneficial effects:

[0021] (1) Integrating the metasurface with the terahertz photoconductive antenna realizes efficient, highly directional, and tunable terahertz radiation.

[0022] (2) Through the structural design of the metasurface, dynamic tuning of the terahertz radiation frequency and directivity is achieved, which is significantly superior to traditional antennas.

[0023] (3) The metasurface has a compact structure and is easy to integrate with other optoelectronic devices, enabling miniaturized and high-performance terahertz systems. Description of the Drawings

[0024] Through the following description of the embodiments of the present invention with reference to the drawings, the above content and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0025] Figure 1 Schematically shows a structural diagram of a terahertz photoconductive antenna with a metasurface coupling structure according to an embodiment of the present invention.

[0026] Figure 2 Schematically shows a structural diagram of a metasurface unit according to an embodiment of the present invention. Detailed Embodiments

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0028] Figure 1 Schematically shows a structural diagram of a terahertz photoconductive antenna with a metasurface coupling structure according to an embodiment of the present invention.

[0029] As Figure 1 shown, a terahertz photoconductive antenna with a metasurface coupling structure according to an embodiment of the present invention includes: a photoconductive antenna that generates a photoconductive effect through optical pumping excitation to radiate terahertz waves; and a metasurface unit integrated in the radiation region of the photoconductive antenna for regulating the phase, amplitude, and polarization of terahertz waves. The metasurface is integrated in the radiation region of the photoconductive antenna and forms a tight coupling with the interdigital electrodes. This coupling effect can enhance the radiation efficiency of terahertz waves and improve their directivity.

[0030] In some exemplary embodiments, a photoconductive antenna includes two symmetric interdigital electrodes, and a photoconductive material is disposed between the two interdigital electrodes. When the optical pump light irradiates the photoconductive material, photons are absorbed by the material and electrons are excited to form a photoconductive current. This current changes with time, thereby generating a transient electromagnetic field around the antenna. The interdigital electrodes serve as a conduction path for the current, guiding the current generated by the photoconductive effect to the radiation region of the antenna. Due to the symmetric distribution and interdigital shape of the electrodes, the current forms a uniform distribution in the radiation region, thereby radiating terahertz waves with specific directivity and frequency.

[0031] In the embodiments of the present invention, the two interdigital electrodes are symmetrically distributed. This design helps to ensure that the terahertz waves radiated by the antenna have uniform directivity and high radiation efficiency. The shape of the electrodes is interdigital, that is, having multiple alternating finger-like structures. This design can increase the contact area between the electrodes and the photoconductive material, thereby increasing the current intensity generated by the photoconductive effect. The interdigital electrodes are usually made of metal materials with good conductivity, such as gold, silver, copper, etc. These materials have good conductivity and stability, ensuring that the antenna maintains stable performance during long-term operation. The photoconductive material includes low-doped gallium arsenide or indium gallium arsenide.

[0032] In some exemplary embodiments, the metasurface unit is composed of periodically arranged sub-wavelength structural units, see Figure 2 . The sub-wavelength structural unit refers to an electromagnetic structural unit whose size is smaller than the operating wavelength (i.e., the wavelength of terahertz waves). These units are periodically arranged on the metasurface, jointly constituting a two-dimensional artificial electromagnetic structure for modulating terahertz waves. Optionally, the sub-wavelength structural unit includes one of metal nanostructures or dielectric metasurface units. Among them, the metal nanostructures include one of nanoantennas or nanoholes; and the dielectric metasurface units include high-refractive-index dielectric nanocolumns. The nanoantenna, having a specific shape and size, can receive and emit terahertz waves, and at the same time modulate its phase, amplitude, and polarization; by precisely controlling the size, shape, and arrangement of the holes, the nanohole can achieve the modulation of the transmission, reflection, and scattering characteristics of terahertz waves; the high-refractive-index dielectric nanocolumn is made of a dielectric material with a high refractive index, having a specific shape and size. By changing the arrangement and structural parameters of the nanocolumns, precise modulation of the phase and amplitude of terahertz waves can be achieved.

[0033] In the embodiments of the present invention, the metasurface unit regulates the phase and amplitude of terahertz waves through sub-wavelength structural units to achieve highly directional radiation. The metasurface unit regulates the phase and amplitude of terahertz waves through its sub-wavelength structural units. The special design of the sub-wavelength structural units enables the terahertz waves to interact with them during propagation, thereby changing the phase and amplitude distribution of the terahertz waves. By precisely controlling the shape, size, and arrangement of the sub-wavelength structural units, continuous regulation of the phase of terahertz waves can be achieved. This phase regulation effect enables the terahertz waves to form a specific phase gradient during propagation, thereby achieving effects such as beam deflection and focusing. The sub-wavelength structural units can also regulate the amplitude of terahertz waves. By optimizing the structural parameters, such as changing the shape, size, or material properties of the units, terahertz waves of a specific frequency can be enhanced or attenuated when passing through the metasurface, thereby achieving precise control of the radiation intensity of terahertz waves.

[0034] In the embodiments of the present invention, by changing the structural parameters of the metasurface unit or applying an external electric or magnetic field, dynamic tuning of the terahertz radiation frequency and directivity is achieved. The structural parameters of the metasurface unit include the period, unit shape, and size. The size of the period determines the arrangement density of the sub-wavelength structural units on the metasurface. By adjusting the period, the interaction frequency between the terahertz waves and the sub-wavelength structural units can be changed, thereby achieving regulation of terahertz waves of a specific frequency; the design of the unit shape has an important impact on the phase and amplitude regulation of terahertz waves. By changing the shape of the unit, precise control of the radiation direction of terahertz waves can be achieved, such as achieving effects like beam deflection, splitting, or focusing; the size of the unit determines its interaction strength with terahertz waves. By optimizing the size parameters, terahertz waves of a specific frequency can obtain the maximum radiation efficiency or directivity when passing through the metasurface.

[0035] In the embodiments of the present invention, through micro-nano processing technology, the structural parameters of the metasurface unit, such as the period, unit shape, and size, can be precisely adjusted. This adjustment can change the interaction mode between the sub-wavelength structural units and terahertz waves, thereby achieving dynamic regulation of terahertz radiation characteristics. By applying an external electric or magnetic field and utilizing the electro-tuning or magneto-tuning effect of the material, the response of the material to terahertz waves is regulated by changing the charge distribution or magnetic moment state inside the material.

[0036] Those skilled in the art can understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention can be combined and / or combined in various ways. All such combinations and / or combinations fall within the scope of the present invention.

Claims

1. A terahertz photoconductive antenna with a metasurface coupling structure, characterized in that: include: A photoconductive antenna, wherein the photoconductive antenna generates a photoconductive effect through optical pumping excitation, thereby radiating a terahertz wave; as well as The metasurface unit is integrated in the radiation region of the photoconductive antenna and is used to control the phase, amplitude and polarization of the terahertz wave.

2. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 1, characterized in that: The photoconductive antenna comprises two symmetrical interdigital electrodes, and a photoconductive material is arranged between the two interdigital electrodes.

3. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 1 or 2, characterized in that: The metasurface unit is composed of periodically arranged sub-wavelength structural units.

4. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 2, characterized in that: The photoconductive material includes low-doped gallium arsenide or gallium indium arsenide.

5. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 3, characterized in that: The sub-wavelength structural unit includes one of a metal nanostructure or a dielectric superstructure unit.

6. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 5, characterized in that: The metal nanostructure comprises one of a nanoantenna or a nanohole; and The dielectric meta-unit comprises a high refractive index dielectric nano-column.

7. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 3, characterized in that: The metasurface unit controls the phase and amplitude of the terahertz wave through the subwavelength structure unit to achieve highly directional radiation.

8. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 3, characterized in that: Dynamic tuning of the frequency and directionality of terahertz radiation is achieved by changing the structural parameters of the metasurface unit or applying an external electric field or magnetic field.

9. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 8, characterized in that: The structural parameters of the metasurface unit include period, unit shape and size.

10. The terahertz photoconductive antenna with a metasurface coupling structure according to claim 3, characterized in that: The size of a subwavelength structural unit is smaller than the wavelength of a terahertz wave.

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