Metasurface structure for realizing terahertz up-conversion luminescence

Abstract

The invention discloses a metasurface structure for realizing terahertz up-conversion luminescence, and belongs to the technical field of optics, the metasurface structure comprises a silicon dioxide substrate, a metal microstructure unit and a quantum dot luminescent material, and is innovatively provided with a dielectric isolation layer and a surface plasma enhancement layer, the dielectric isolation layer reduces the quenching effect of metal on quantum dots, and the surface plasma enhancement layer enhances the surface plasma on the quantum dots. The surface plasma enhancement layer enhances a local electric field. The metasurface structure for realizing terahertz up-conversion luminescence can effectively improve the terahertz visible light up-conversion efficiency, realizes high-sensitivity and quick-response terahertz detection at room temperature, improves the detection sensitivity, simplifies a detection system, has a wide application prospect in the fields of biomedicine, security inspection, communication and the like, and has a wide application prospect in the fields of biomedicine, security inspection, communication and the like. And the practical application development of the terahertz technology is promoted.

Description

Technical Field

[0001] The present invention belongs to the field of optical technology, and in particular relates to a super surface structure for realizing terahertz up-conversion luminescence. Background Art

[0002] Terahertz waves occupy a unique position in the electromagnetic spectrum, between microwaves and infrared regions. They have many excellent properties, such as low single photon energy and strong penetration into non-polar substances such as biological tissues, which makes them very promising in biomedical imaging, early disease diagnosis and other fields; each substance has a unique absorption and emission spectrum in the terahertz band, namely fingerprint characteristics, which has obvious advantages in the field of security inspection, such as drug and explosive detection; the broadband nature of terahertz waves also brings new opportunities for high-speed communications.

[0003] However, existing terahertz detection technologies have many limitations. Although thermal radiation meters and pyroelectric detectors have high sensitivity, thermal radiation meters require deep cryogenic cooling, which makes the equipment costly and has limited application scenarios; pyroelectric detectors respond slowly, with a response time of milliseconds. Although Schottky diodes and field-effect transistors can work at room temperature and have a response time of nanoseconds or picoseconds, they have low sensitivity and a limited detection range, usually below ~1 terahertz, which seriously restricts the widespread application of terahertz technology. Summary of the invention

[0004] The purpose of the present invention is to provide a metasurface structure for realizing terahertz up-conversion luminescence, so as to solve the problem that the Schottky diode and field effect transistor proposed in the above background technology can work at room temperature and have a response time of nanoseconds or picoseconds, but have low sensitivity and limited detection range, usually lower than ~1 terahertz, which seriously restricts the widespread application of terahertz technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a metasurface structure for realizing terahertz up-conversion luminescence, comprising a silicon dioxide substrate, a metal microstructure unit, and a quantum dot luminescent material, wherein the metal microstructure unit is periodically arranged on the surface of the silicon dioxide substrate, the metal microstructure unit is a center-open resonant ring, the quantum dot luminescent material is covered on the silicon dioxide substrate and the metal microstructure unit, the quantum dot luminescent material exists in the form of a thin film, a dielectric isolation layer is arranged between the metal microstructure unit and the quantum dot luminescent material, the quantum dot luminescent material is covered with a surface plasma enhancement layer, and the surface plasma enhancement layer is composed of silver nanoparticles.

[0006] In a further embodiment, the surface of the silicon dioxide substrate is specially treated, and a titanium dioxide anti-reflection film with a thickness of 10-30 nm is deposited on the surface by chemical vapor deposition.

[0007] In a further embodiment, the corners of the central split ring resonator of the metal microstructure unit are designed with rounded corners.

[0008] In a further embodiment, the quantum dot luminescent material is doped with rare earth elements, and the doping concentration is 0.1-1%.

[0009] In a further embodiment, a metal border is provided in the edge region of the metasurface structure, and the material of the metal border is the same as that of the metal microstructure unit.

[0010] In a further embodiment, the dielectric isolation layer is grown on the metal microstructure unit by atomic layer deposition technology. The surface plasmon enhancement layer prepares silver nanoparticles by chemical solution method and uniformly deposits them on the surface of the quantum dot luminescent material by self-assembly technology.

[0011] Technical effects and advantages of the present invention:

[0012] The metasurface structure for realizing terahertz upconversion luminescence effectively improves the upconversion efficiency of terahertz to visible light through the synergistic effect of the dielectric isolation layer and the surface plasmon enhancement layer. The detection sensitivity is more than twice that of the traditional structure. It can work at room temperature, and the response time is shortened to within 30 ns, meeting the requirements of rapid detection.

[0013] The dielectric isolation layer reduces the adverse effects of the metal microstructure unit on the quantum dot luminescent material, improving the luminescence efficiency and stability. The surface plasmon enhancement layer enhances the local electric field, further improving the detection performance.

[0014] By using the innovative principle of terahertz to visible light upconversion, the detection of terahertz waves is cleverly converted into the detection of visible light. With the help of mature visible light detection technology, it not only simplifies the structure and complexity of the terahertz detection system, reduces the system cost, but also improves the stability and reliability of the system, making the terahertz detection system easier to build and maintain. The metasurface structure for realizing terahertz upconversion luminescence can effectively improve the terahertz to visible light upconversion efficiency, achieve high-sensitivity and fast-response terahertz detection at room temperature, improve the detection sensitivity, and at the same time simplify the detection system, having broad application prospects in the fields of biomedicine, security inspection, communication, etc., and promoting the practical application development of terahertz technology. Description of the Drawings

[0015] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 is a schematic structural diagram of the present invention;

[0017] Figure 2 is a cross-sectional view of the present invention.

[0018] In the figure: 1, silica substrate; 2, metal microstructure unit; 3, dielectric isolation layer; 4, quantum dot luminescent material; 5, surface plasmon enhancement layer. Specific embodiments

[0019] In the following description, numerous specific details are given to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details. In other instances, well-known technical features are not described to avoid obscuring the present invention.

[0020] Unless otherwise defined, the directions such as up, down, left, right, front, back, inside, and outside referred to herein are based on the up, down, left, right, front, back, inside, and outside directions in the figures shown in the present invention, and are hereby explained together.

[0021] The present invention provides a metasurface structure for realizing terahertz upconversion luminescence as shown in Figure 1-2 , including a silica substrate 1, a metal microstructure unit 2, and a quantum dot luminescent material 4. The metal microstructure units 2 are periodically arranged on the surface of the silica substrate 1. The metal microstructure unit 2 is a center-opening resonant ring. The quantum dot luminescent material 4 covers the silica substrate 1 and the metal microstructure unit 2. A dielectric isolation layer 3 is provided between the metal microstructure unit 2 and the quantum dot luminescent material 4. The material of the dielectric isolation layer 3 is alumina, and the thickness is 10 - 30 nm. The dielectric isolation layer 3 is grown on the metal microstructure unit 2 by atomic layer deposition technology. A surface plasmon enhancement layer 5 is covered on the quantum dot luminescent material 4. The surface plasmon enhancement layer 5 is composed of silver nanoparticles, and the particle size is 20 - 50 nm. The surface plasmon enhancement layer 5 is prepared by chemically synthesizing silver nanoparticles in a solution and uniformly depositing them on the surface of the quantum dot luminescent material 4 by self-assembly technology;

[0022] The silica substrate 1 is used to support the entire metasurface structure. The purity of the silica substrate 1 is not less than 99.9%, the thickness is between 0.5 - 2 mm, and the surface roughness is less than 10 nm. The surface of the silica substrate 1 is specially treated, and a titanium dioxide antireflection film with a thickness of 10 - 30 nm is deposited on its surface by chemical vapor deposition;

[0023] The material of the metal microstructural unit 2 is one or more of gold, silver, and copper, with a purity of not less than 99.5%. The outer contour side length of the center-opening split ring resonator is 12 μm, the slit width of the microstructural unit is less than 2 μm, the periodic pitch between adjacent microstructural units is 8 μm, and the corners of the center-opening split ring resonator of the metal microstructural unit 2 are designed with rounded corners;

[0024] The quantum dot luminescent material 4 is one or more of CdSe, CdTe, and ZnSe. The quantum dot luminescent material 4 exists in the form of a thin film with a thickness of 30 - 80 nm, and the surface flatness deviation of the thin film is within ±5 nm. The quantum dot luminescent material 4 is doped with rare earth elements, and the rare earth elements are one or more of europium and terbium, with a doping concentration of 0.1 - 1%;

[0025] A metal frame is provided in the edge region of the metasurface structure. The material of the metal frame is the same as that of the metal microstructural unit 2, with a width of 50 - 150 nm. At the same time, the metasurface structure is integrated with a micro-nano optical lens array. The focal length of the micro-nano optical lens array is 1 - 5 mm. Through the synergistic effect of the dielectric isolation layer 3 and the surface plasmon enhancement layer 5, the up-conversion efficiency of terahertz visible light is effectively improved. The detection sensitivity is more than twice that of the traditional structure, and it can work at room temperature. The response time is shortened to within 30 ns, meeting the requirements of rapid detection. The dielectric isolation layer 3 reduces the adverse effects of the metal microstructural unit 2 on the quantum dot luminescent material 4, improving the luminescence efficiency and stability. The surface plasmon enhancement layer 5 enhances the local electric field, further improving the detection performance.

[0026] The standard parts used in the present invention can all be purchased from the market. The special-shaped parts can be customized according to the description in the specification and the drawings. The specific connection methods of each part all adopt conventional means such as bolts, rivets, and welding that are mature in the prior art. The machines, parts, and equipment all adopt conventional models in the prior art. In addition, the circuit connection adopts the conventional connection method in the prior art, which will not be elaborated here. The control method of the present invention is controlled by a controller, and the control circuit of the controller can be realized by simple programming by those skilled in the art. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0027] In the description of the present invention, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0028] Working principle:

[0029] The metasurface structure for realizing terahertz upconversion luminescence, when terahertz waves are perpendicularly incident on the metasurface, the periodically arranged central split-ring metal microstructure units 2 will have a strong interaction with the terahertz waves. Due to the special design of the metal microstructure units 2, a local electric field enhancement effect will occur at the slit. This enhancement effect stems from the scattering and resonance of the metal microstructure on the terahertz waves, which can concentrate the energy of the terahertz waves near the slit, significantly increasing the electric field strength at the slit, and an enhancement effect of up to three orders of magnitude can be achieved;

[0030] After the local electric field enhancement is generated by the terahertz waves exciting the metal microstructure units 2, the dielectric isolation layer 3 plays a key isolation and protection role. On the one hand, it can reduce the quenching effect of the metal microstructure units 2 on the quantum dot luminescent material 4. The free electrons in the metal will have an energy transfer with the quantum dots, resulting in a decrease in the luminescence efficiency of the quantum dots. The dielectric isolation layer 3 can effectively prevent this energy transfer and maintain the luminescence performance of the quantum dots. On the other hand, the dielectric isolation layer 3 has good insulation, can stabilize the local electric field, prevent electric field leakage, and ensure that the electric field energy effectively acts on the quantum dot luminescent material 4;

[0031] When the local electric field generated by the terahertz wave excitation acts on the surface plasmon enhancement layer 5, the silver nanoparticles will undergo surface plasmon resonance. This resonance will further enhance the local electric field strength, greatly optimizing the electric field environment around the quantum dot luminescent material 4. The near-field enhancement effect generated by the surface plasmon resonance can more efficiently transfer the energy of the terahertz waves to the quantum dots and improve the excitation efficiency of the quantum dots;

[0032] Under the synergistic effect of the above multi-layer structure, the quantum dot luminescent material 4 absorbs the enhanced terahertz wave energy, and the electrons inside the quantum dots are excited to higher energy levels. When the electrons transition from the higher energy levels back to the lower energy levels, they will release energy in the form of visible light, realizing the upconversion process of terahertz to visible light. Due to the optimization of the dielectric isolation layer 3 and the surface plasmon enhancement layer 5, the luminescence efficiency of the quantum dots is significantly improved, and the intensity of the emitted visible light is higher;

[0033] Finally, by using a visible light detector to detect the visible light emitted by the quantum dots and converting the optical signal into an electrical signal, since there is a corresponding relationship between the intensity of the visible light and the intensity of the incident terahertz waves, after processing and analyzing the electrical signal, relevant information about the terahertz waves, such as intensity, frequency, etc., can be indirectly obtained, thus realizing the detection of terahertz waves.

[0034] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A metasurface structure for realizing terahertz upconversion luminescence, comprising a silicon dioxide substrate (1), a metal microstructure unit (2), and a quantum dot luminescent material (4), characterized in that: The metal microstructure units (2) are periodically arranged on the surface of a silicon dioxide substrate (1); the metal microstructure units (2) are center-open resonant rings; the quantum dot luminescent material (4) covers the silicon dioxide substrate (1) and the metal microstructure units (2); the quantum dot luminescent material (4) exists in the form of a thin film; a dielectric isolation layer (3) is provided between the metal microstructure units (2) and the quantum dot luminescent material (4); a surface plasma enhancement layer (5) is covered on the quantum dot luminescent material (4); and the surface plasma enhancement layer (5) is composed of silver nanoparticles.

2. The metasurface structure for realizing terahertz upconversion luminescence according to claim 1, characterized in that: The surface of the silicon dioxide substrate (1) is specially treated, and a titanium dioxide anti-reflection film with a thickness of 10-30 nm is deposited on the surface by chemical vapor deposition.

3. The metasurface structure for realizing terahertz upconversion luminescence according to claim 1, characterized in that: The corners of the central open resonant ring of the metal microstructure unit (2) are designed with rounded corners.

4. The metasurface structure for realizing terahertz upconversion luminescence according to claim 1, characterized in that: The quantum dot luminescent material (4) is doped with rare earth elements, with a doping concentration of 0.1-1%.

5. The metasurface structure for realizing terahertz upconversion luminescence according to claim 1, characterized in that: A circle of metal frame is arranged at the edge region of the super surface structure, and the material of the metal frame is the same as that of the metal microstructure unit (2).

6. The metasurface structure for realizing terahertz upconversion luminescence according to claim 1, characterized in that: The dielectric isolation layer (3) is grown on the metal microstructure unit (2) by atomic layer deposition technology, and the surface plasma enhancement layer (5) is prepared by a chemical solution method to prepare silver nanoparticles, and the silver nanoparticles are uniformly deposited on the surface of the quantum dot light-emitting material (4) by using a self-assembly technology.

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