Filter with infrared multi-band coordinated response capability

Abstract

The present application relates to a filter with infrared multi-band coordinated response capability, which excites surface plasma by etching a sub-wavelength (0.01-2 times wavelength) hollow circular hole-metal ring structure of different sizes on a metal film, forming a surface plasma enhanced light transmission effect for infrared medium-wave band and infrared long-wave band light. At the same time, the interaction between different geometric features in the unit structure is regulated to achieve the absorption of the atmospheric window infrared non-communication band, achieving the effect of filtering electromagnetic waves of different bands, and the metal part of the metal film except the open hole structure forms a continuous conductive structure to achieve the shielding effect of electromagnetic waves.

Description

Technical Field

[0001] The present application relates to the field of electromagnetic protection technology, and in particular to a filter having infrared multi-band coordinated response capability. Background Art

[0002] As an optical frequency selective device, filters can pass electromagnetic waves of specific wavelengths to achieve filtering and wave absorption. They are widely used in optical channels of photoelectric detection systems.

[0003] However, according to the different signal transmission bands, the photoelectric detection system can be divided into a single-band detection system and a multi-band composite detection system. At the same time, infrared detector technology is developing at a rapid pace, and its threat is also increasing, bringing new challenges to the military and security fields. In this increasingly complex situation, the research and development of filters with multi-functional integration, infrared multi-band coordinated response and microwave band electromagnetic protection is particularly important, so that it can be effectively concealed or effectively protected in various environments. Summary of the invention

[0004] Based on this, it is necessary to provide a filter with infrared multi-band coordinated response capability that can achieve multi-band high transmittance of infrared light and shield ultra-wideband electromagnetic waves in order to address the above technical problems.

[0005] A filter with infrared multi-band coordinated response capability, comprising: a metal film, and a plurality of light-transmitting units etched on the metal film;

[0006] The plurality of light-transmitting units are periodically arranged on the metal film, each of the light-transmitting units is a hollow circular hole-metal circular ring combination structure that runs through the thickness direction of the metal film and has a sub-wavelength size, and each of the hollow circular hole-metal circular ring combination structures has the same size;

[0007] The metal parts on the metal film except the light-transmitting unit are continuous conductive structures;

[0008] The thickness of the metal film is greater than 0.05 um and less than or equal to 0.1 um.

[0009] In one embodiment, in the hollow circular hole-metal circular ring combination structure of each light-transmitting unit, the centers of the hollow circular hole and the metal circular ring coincide with each other, and the radius of the hollow circular hole is larger than the outer radius of the metal circular ring.

[0010] In one embodiment, the thickness of the metal film is 0.1 um.

[0011] In one embodiment, the distance between the centers of the light-transmitting units is 2.5 um.

[0012] In one embodiment, the radius of the hollow circular hole structure in each of the light-transmitting units is in the range of 1.45 um-2.15 um.

[0013] In one embodiment, the radius of the hollow circular hole structure in each of the light-transmitting units is 2.05 um.

[0014] In one embodiment, the outer radius of the metal ring structure in each light-transmitting unit is 1.2 um.

[0015] In one embodiment, the inner radius of the metal ring structure in each light-transmitting unit is 1.1 um.

[0016] In one embodiment, the metal film is made of gold.

[0017] The above-mentioned filter with infrared multi-band coordinated response capability excites surface plasma by etching a sub-wavelength (0.01-2 times the wavelength) hollow circular hole-metal circular ring combination structure of different sizes on the metal film, thereby forming a surface plasma enhanced light transmission effect for light of a specific wavelength. At the same time, different types of resonance effects are formed through the interaction between different geometric features in the structure, thereby regulating the movement of the transmission peak of the infrared band of the atmospheric window, thereby achieving the effect of electromagnetic wave filtering in the infrared medium wave band and the infrared long wave band, and the metal part of the metal film except the hollow circular hole-metal circular ring combination structure forms a continuous conductive structure to achieve a shielding effect on microwaves. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a filter having infrared multi-band coordinated response capability in one embodiment;

[0019] Figure 2 is a transmittance spectrum of a light-transmitting unit under different radii r1 in one embodiment;

[0020] Figure 3 This is a diagram of the shielding effectiveness in the radar band 1-18GHz when the filter parameters in an experiment are set to a period of 5um, a radius r1 of 2.05um, a radius r2 of 1.2um, a radius r3 of 1.1um, and an Au film thickness of 0.1um. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] In response to the demand for filters that integrate infrared multi-band coordinated response and microwave band electromagnetic protection in existing application scenarios, a filter with infrared multi-band coordinated response capability is provided in the application. The filter includes: a metal film, and a plurality of light-transmitting units etched on the metal film. Multiple light-transmitting units are periodically arranged on the metal film, and each light-transmitting unit is a hollow circular hole-metal ring combination structure that runs through the thickness direction of the metal film and has a sub-wavelength size, and each hollow circular hole-metal ring combination structure has the same size. Except for the light-transmitting units, the rest of the metal part on the metal film is a continuous conductive structure. At the same time, the thickness of the metal film is greater than 0.05um and less than or equal to 0.1um.

[0023] In this embodiment, a sub-wavelength (0.01-2 times the wavelength) hollow circular hole-metal circular ring combination structure of different sizes is etched on the metal film to excite the surface plasma, thereby forming a surface plasma enhanced light transmission effect for light of a specific wavelength. At the same time, different types of resonance effects are formed by the interaction between different geometric features in the hollow circular hole-metal circular ring combination structure, thereby regulating the movement of the transmission peak of the infrared band of the atmospheric window, and achieving the effect of electromagnetic wave filtering in the infrared medium wave band and the infrared long wave band. Since the surface plasma structure is simple and centrally symmetrical, it can achieve light transmission for incident electromagnetic waves with different polarization directions.

[0024] At the same time, after etching away the opening area, the remaining metal forms a continuous conductive ultra-wideband shielding layer, which achieves a shielding effectiveness of more than 60dB in the microwave band of 1-18GHz. In the prior art, most of the filters that can achieve this effect are filters that use grids and multi-layer film structures. It is difficult to solve the compatibility between infrared transmittance and microwave shielding effectiveness, and the overall film thickness is too large and the adhesion between the films is not strong, which leads to easy falling off between film layers of different materials and the response band involves multiple infrared atmospheric windows.

[0025] Furthermore, the infrared multi-band cooperative response filter proposed in this method has the advantages of small size and easy integration, and the micro-nano structure has higher resolution and better imaging effect, making the filter suitable for filtering information transmission in various situations. The key is that by combining the hollow circular hole structure and the metal ring structure, the response band of the filter is broken through from a single response band to a multi-response band, meeting the requirements of multi-band cooperative response of the infrared detection system. Under the premise of meeting the surface plasma transmission, the lower the proportion of the opening area of ​​the metal film, the more beneficial it is for the filter to improve the microwave shielding efficiency and the more conducive it is to the stability of the structure. And the transmittance of the device for different light transmission bands is not less than 30%.

[0026] In this embodiment, the hollow circular hole-metal circular ring combination structure of each light-transmitting unit has the centers of the hollow circular hole and the metal circular ring coincident, and the radius of the hollow circular hole is larger than the outer radius of the metal circular ring. The structure of the entire filter is as follows: Figure 1 As shown, a plurality of periodically arranged light-transmitting units 2 are arranged on the metal film 1, each light-transmitting unit 2 runs through the thickness direction of the metal film, and the continuous conductive structure is the metal part of the metal film 1 except the light-transmitting unit 2. The radius r1 of the hollow circular hole is greater than the outer radius r2 of the metal ring, and greater than the inner radius r3 of the metal ring, that is, each light-transmitting unit has a concentric metal ring arranged in the hollow circular hole.

[0027] In this embodiment, the distance between the centers of each light-transmitting unit is 2.5um, the radius r1 of the hollow circular hole structure in each light-transmitting unit is in the range of 1.45um-2.15um, the outer radius r2 of the metal ring structure in each light-transmitting unit is 1.2um, and the inner radius r3 of the metal ring structure in each light-transmitting unit is 1.1um. Such a light-transmitting unit size can form a surface plasma enhanced light transmission effect in the range of 3-5um in the infrared medium wave band and 8-12um in the infrared long wave band.

[0028] Preferably, the radius of the hollow circular hole structure in each light-transmitting unit is 2.05 um.

[0029] Preferably, the thickness of the metal film is 0.1 um.

[0030] In this embodiment, the metal film 1 is made of gold.

[0031] Next, the transmittance of the hollow circular hole-metal ring structure in the infrared medium wave band and the infrared long wave band was simulated, and the simulation experiment was implemented using the FDTD finite time-domain difference method. The specific experimental environment parameters are set as follows: According to the Floquet theorem, using periodic boundary conditions, only one periodic unit structure of the research object needs to be considered in the actual CST Studio calculation. This treatment can not only effectively reduce the calculation time, but also obtain the electromagnetic field distribution of the unit structure. Therefore, the X and Y boundaries of the unit structure are set as periodic boundary conditions, and the Z boundary is set as an open boundary condition. In addition, the free electron gas Drude model is used to describe the gold material, and the specific parameters are: ω p =1.374e16 rad / s, γ =4.08e13 rad / s, ε ∞ = 1. The quartz material is selected from the sample in the CST software material library.

[0032] The electromagnetic wave is incident vertically from the metal film 1 to the light-transmitting unit 2. In the specific experiment, the transmission peak position in the range of 3-5um in the infrared medium wave band and 8-12um in the infrared long wave band can be achieved by adjusting the geometric parameters of the light-transmitting unit, such as Figure 2 At the same time, electromagnetic shielding is performed for the microwave band 1-18GHz, as shown in Figure 3 shown.

[0033] The detailed parameters are as follows:

[0034] In this embodiment, the infrared multi-band cooperative response filter adopts a metal film 1 with a thickness h1 of 0.1um; the radius r1 of the light-transmitting unit 2 is 1.45um, 1.55um, 1.65um, 1.75um, 1.85um, 1.95um, 2.05um, and 2.15um respectively; the radius r2 of the light-transmitting unit 2 remains unchanged at 1.2um; the radius r3 of the light-transmitting unit 2 remains unchanged at 1.1um; the distance between the center points of adjacent light-transmitting units is 5um;

[0035] By adjusting the radius r1 of the light-transmitting unit 2, as Figure 3 As shown, as the radius r1 in the light-transmitting unit 2 increases, a transmission peak appears in the range of 3-5μm in the infrared medium wave band, and the transmission peak shifts in the direction of smaller wavelength as the radius r1 increases, and finally the transmission peak splitting phenomenon occurs when the radius r1 reaches 2.15um. At the same time, as the radius r1 increases, a transmission peak also appears in the range of 8-12μm in the infrared long wave band, and increases with the increase of the radius r1, and gradually covers the entire infrared long wave band 8-12μm range. It is worth noting that an absorption valley appears in the range of 5-8μm in the infrared non-communication band, forming a stop band, which makes it impossible to transmit signals in the non-communication band. By comparison, the radii r1, r2, r3 and the distance P between the center points of adjacent light-transmitting units were finally selected as 2.05um, 1.25um, 1.1um and 5um, respectively.

[0036] Furthermore, the transmittance of the infrared multi-band cooperative response filter in the microwave band of 1-18 GHz was simulated under this parameter. The results are as follows: Figure 3 As shown, the infrared multi-band cooperative response filter has a shielding effect of more than 60dB in the microwave band range of 1-18GHz.

[0037] The above-mentioned filter with infrared multi-band coordinated response capability excites surface plasma by etching a sub-wavelength (0.01-2 times the wavelength) hollow circular hole-metal ring combination structure of different sizes on the metal film, thereby forming a surface plasma enhanced light transmittance effect for infrared medium-wave band 3-5um and infrared long-wave band 8-12μm wavelength light. At the same time, after etching away the opening area, the remaining metal forms a continuous conductive structure to constitute an ultra-wideband shielding layer, achieving a shielding effectiveness of more than 60dB in the microwave band 1-18GHz band.

[0038] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0039] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A filter with infrared multi-band coordinated response capability, characterized in that: The filter has the ability to transmit light with a wavelength of 3-5 μm in the infrared medium wave band and 8-12 μm in the infrared long wave band, and at the same time achieves a shielding effect greater than 60 dB in the microwave band of 1-18 GHz, comprising: a metal film, and a plurality of light-transmitting units etched on the metal film; The plurality of light-transmitting units are periodically arranged on the metal film, each of the light-transmitting units is a hollow circular hole-metal circular ring combination structure that runs through the thickness direction of the metal film and has a sub-wavelength size, each of the hollow circular hole-metal circular ring combination structures has the same size, and the distance between the centers of the light-transmitting units is 2.5 um; The hollow circular hole-metal circular ring combination structure of each light-transmitting unit, the centers of the hollow circular hole and the metal circular ring coincide, and the radius of the hollow circular hole is greater than the outer radius of the metal circular ring, wherein the radius of the hollow circular hole structure in each light-transmitting unit is 2.05um, and the outer radius and inner radius of the metal circular ring structure in each light-transmitting unit are 1.2um and 1.1um respectively; The metal parts on the metal film except the light-transmitting unit are continuous conductive structures; The thickness of the metal film is 0.1 um, and the metal film is made of gold material.

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