Narrow-band infrared absorber based on all-dielectric metasurface

Abstract

The present invention provides a narrow-band infrared absorber based on an all-dielectric metasurface, comprising a substrate, a dielectric base layer, a dielectric loss layer and a dielectric resonator array, wherein the dielectric base layer is arranged on the substrate; the dielectric loss layer is arranged on the dielectric base layer; and the dielectric resonator array is arranged on the dielectric loss layer. The present invention uses a high-refractive-index dielectric resonator to replace a metal resonator, which has no ohmic loss, thereby achieving narrow-band absorption with a high quality factor, and the dielectric loss layer and the dielectric resonator array are designed in layers, and a narrow-band response is achieved by using a dielectric resonator that is lossless in the mid-infrared band; the resonance effect is enhanced by introducing a dielectric loss layer, thereby achieving an improvement in the absorption efficiency in the mid-infrared band, and overcoming the contradiction between the resonator loss and the absorption bandwidth.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano optical devices, and specifically provides a narrow-band infrared absorber based on an all-dielectric metasurface. Background Art

[0002] The mid-infrared band mainly refers to infrared radiation with a wavelength of 2.5 to 25 μm, including two atmospheric window areas, the mid-infrared band and the long-wave infrared band, covering the characteristic frequency area and the fingerprint area. It is of great significance for identifying functional groups and distinguishing compounds with similar structures. It has important application value in the fields of optical sensing, environmental monitoring and spectral detection. Therefore, it is urgent to develop mid-infrared band narrow-band absorbers for infrared spectral detection, biosensors, spectrometers, etc. However, due to the low absorption efficiency of natural materials and the inability to control their absorption bandwidth, the application of infrared absorbers is hindered. The design and development of new narrow-band infrared absorbers are of great significance.

[0003] Metasurface is a two-dimensional form of metamaterial, which is formed by subwavelength microstructures arranged in a certain pattern. Its electromagnetic properties do not depend on the natural properties of the material. Through the design of the microstructure, a specific spectral response can be achieved. Metasurfaces have been widely studied in recent years. Metasurface absorbers based on metal-dielectric-metal sandwich structures can achieve nearly 100% absorption at specific wavelengths. On the one hand, due to the limitation of the Ohmic loss effect in metal resonators, absorbers based on metal materials are difficult to achieve narrowband absorption; on the other hand, the photothermal effect of metal materials is not conducive to photoelectric conversion in biosensors and detectors. Metasurfaces based on dielectric materials have the characteristics of low loss, which can achieve narrower resonance bandwidth and higher quality factor, but the low loss of the resonator affects the absorption efficiency of the absorber. For the near-infrared band, the use of lossy dielectric materials with high refractive index can improve the absorption rate under the premise of losing a certain bandwidth; however, in the mid-infrared band, due to the lack of high refractive index dielectric materials, the size of the resonator becomes larger, resulting in the dielectric resonator still facing the contradictory relationship between resonator loss and absorption bandwidth. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a narrow-band infrared absorber based on an all-dielectric metasurface, which mainly designs a dielectric loss layer and a dielectric resonator array in a layered manner, and uses dielectric resonators that are lossless in the mid-infrared band to achieve narrow-band response; by introducing a dielectric loss layer to enhance the resonance effect, the absorption efficiency in the mid-infrared band is enhanced, thereby overcoming the contradiction between resonator loss and absorption bandwidth.

[0005] The narrow-band infrared absorber based on the all-dielectric metasurface provided by the present invention comprises:

[0006] substrate;

[0007] A dielectric base layer, which is disposed on the substrate;

[0008] A dielectric loss layer, which is disposed on the dielectric base layer;

[0009] a dielectric resonator array disposed on the dielectric loss layer;

[0010] The dielectric resonator array includes N dielectric resonators arranged in a periodic manner, wherein N is a positive integer, and the dielectric resonator is a microstructure;

[0011] The loss rate in the mid-infrared band in the dielectric substrate or dielectric resonator array is smaller than the loss rate in the dielectric loss layer;

[0012] The refractive index of the dielectric substrate in the mid-infrared band is smaller than the refractive index of the dielectric resonator in the mid-infrared band.

[0013] Preferably, the substrate is a silicon wafer or a quartz wafer.

[0014] Preferably, the dielectric base layer is made of calcium fluoride or magnesium fluoride, and its thickness is 1000-100000 nm.

[0015] Preferably, the dielectric loss layer is made of a material whose loss rate in the mid-infrared band is not zero, and has a thickness of 50 to 500 nm.

[0016] Preferably, the dielectric loss layer is a patterned dielectric film or a complete continuous dielectric film.

[0017] Preferably, the material used for the dielectric resonator is germanium, and its thickness is 100-10000 nm.

[0018] Preferably, the dielectric resonator is a cylindrical, rectangular or polygonal microstructure.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0020] 1. The present invention uses a high-refractive-index dielectric resonator to replace a metal resonator, which has no ohmic loss and can thus achieve narrow-band absorption with a high quality factor.

[0021] 2. The present invention designs the dielectric loss layer and the dielectric resonator array in layers, and realizes the narrowband response of the absorber in the lossless resonator; by introducing the lossy dielectric layer, the resonance effect is improved, the absorption efficiency in the mid-infrared band is improved, the contradiction between the resonator loss and the absorption bandwidth is overcome, and the narrowband high absorption in the mid-infrared band is realized.

[0022] 3. The metasurface breaks through the limitations of the dispersion characteristics of natural materials and can achieve narrow-band high absorption at any wavelength, and the structural scheme of the present invention is expected to be extended to other bands.

[0023] 4. The polarization sensitivity of the present invention can be adjusted by changing the design of the dielectric resonator, and the polarization insensitivity can be adjusted, and polarization selection can also be achieved.

[0024] 5. The metasurface structure of the present invention is fully compatible with CMOS technology and is easy to integrate with existing devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the distribution of each layer of a narrow-band infrared absorber based on an all-dielectric metasurface provided by the present invention;

[0026] Figure 2 is a side view of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to Embodiment 1 of the present invention;

[0027] Figure 3 is a top view of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to Embodiment 1 of the present invention;

[0028] Figure 4 is an absorption spectrum diagram of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to Embodiment 1 of the present invention;

[0029] Figure 5 is a side view of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to Embodiment 2 of the present invention;

[0030] Figure 6 is a top view of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to Embodiment 2 of the present invention;

[0031] Figure 7 is an absorption spectrum diagram of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to the second embodiment of the present invention;

[0032] Figure 8 This is an absorption spectrum diagram of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to Example 3 of the present invention.

[0033] The reference numerals include: substrate 1, dielectric base layer 2, dielectric loss layer 3, dielectric resonator array 4, and dielectric resonator 4-1. DETAILED DESCRIPTION

[0034] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0036] Distribution of each layer of narrow-band infrared absorber based on all-dielectric metasurface:

[0037] Figure 1 The distribution of each layer of the narrow-band infrared absorber based on the all-dielectric metasurface provided according to the present invention is shown.

[0038] like Figure 1 As shown, the structure of the narrow-band infrared absorber based on the all-dielectric metasurface includes: a substrate 1, a dielectric base layer 2, a dielectric loss layer 3 and a dielectric resonator array 4. The dielectric base layer 2 is arranged on the substrate 1; the dielectric loss layer 3 is arranged on the dielectric base layer 2; and the dielectric resonator array 4 is arranged on the dielectric loss layer 3.

[0039] The substrate 1 is an integral supporting structure and can be made of silicon wafers, quartz wafers, etc. The substrate 1 of the narrow-band infrared absorber based on the all-dielectric metasurface can be replaced with an uncooled infrared detection pixel unit to achieve functional integration.

[0040] The dielectric base layer 2 may be made of a material with a low refractive index and low or no loss in the mid-infrared band, such as calcium fluoride or magnesium fluoride, etc. The thickness of the dielectric base layer 2 is set to 1000-100000 nm.

[0041] The dielectric loss layer 3 can be made of a material having loss in the mid-infrared band, such as silicon nitride, etc. The thickness of the dielectric loss layer 3 is 50-500 nm. The dielectric loss layer 3 can be made of a patterned dielectric film or a complete and continuous dielectric film.

[0042] The dielectric resonator array 4 includes N dielectric resonators arranged in a periodic manner, where N is a positive integer. The dielectric resonator can be made of materials with high refractive index and low or no loss in the mid-infrared band, such as germanium. The dielectric resonator can be processed into a cylindrical, rectangular or polygonal microstructure with a thickness of 100 to 10,000 nm through micro-nano processing technology. The function of the dielectric resonator array 4 is to generate a narrowband resonance with a high quality factor, localize the energy in the N dielectric resonators, and then conduct it to the dielectric loss layer 3 for absorption. The low or no loss dielectric resonator material helps to improve the quality factor of the absorber and obtain a narrow bandwidth. All the absorbed energy is concentrated in the dielectric loss layer 3, and the high energy density that can be obtained is conducive to the application of narrow-band infrared absorbers based on all-dielectric metasurfaces in the fields of detection and sensing.

[0043] It is necessary to ensure that: the loss rate of the mid-infrared band in the dielectric base layer 2 or the dielectric resonator array 4 is smaller than the loss rate in the dielectric loss layer 3; the refractive index of the dielectric base layer 2 for the mid-infrared band is smaller than the refractive index of the dielectric resonator for the mid-infrared band.

[0044] Embodiment 1:

[0045] Figure 2 The side-view structure of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to the first embodiment of the present invention is shown.

[0046] Figure 3 The top-down structure of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to Embodiment 1 of the present invention is shown.

[0047] like Figure 2 and Figure 3 As shown, the distribution of each layer of the narrow-band infrared absorber based on the all-dielectric metasurface of Example 1 is Figure 1 The contents of the parts are consistent and will not be repeated here. Among them, the substrate 1 is made of silicon wafer; the dielectric base layer 2 is made of calcium fluoride with a thickness of 5000nm; the dielectric loss layer 3 is made of silicon nitride with a thickness of 100nm; the dielectric loss layer 3 is patterned by micro-nano processing and has the same diameter as the dielectric resonator 4-1; the dielectric resonator 4-1 is made of germanium with a cylindrical shape and a microstructure realized by micro-nano processing; the structural parameters of the germanium cylinder are a diameter of 2000nm, a height of 4380nm, and a period of 3380nm.

[0048] Figure 4 The absorption spectrum of the narrow-band infrared absorber based on the all-dielectric metasurface provided according to the first embodiment of the present invention is shown.

[0049] like Figure 4 As shown, the finite difference time domain method is used to perform numerical simulation calculations on the narrow-band infrared absorber based on the all-dielectric metasurface in Example 1, and the following conclusions are obtained: at the mid-infrared band with a wavelength of 6.612 microns, the absorption rate of the present invention is 89.6%, the bandwidth is 1.08nm, and the quality factor is 6122. Based on the above data analysis, the present invention is effective and superior.

[0050] It should be noted that the absorptivity of the present invention is obtained by the calculation formula A=1-TR, wherein A represents absorptivity, T represents transmittance, and R represents reflectivity; the quality factor of the present invention is obtained according to the calculation formula Q=lambda / FWHM, wherein Q is the quality factor, lambda represents the absorption center wavelength, and FWHM represents the half-peak width.

[0051] Embodiment 2:

[0052] Figure 5The side-view structure of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to the second embodiment of the present invention is shown.

[0053] Figure 6 The top-down structure of a narrow-band infrared absorber based on an all-dielectric metasurface provided according to the second embodiment of the present invention is shown.

[0054] like Figure 5 and Figure 6 As shown, the structure of the embodiment 1 is different from that of the embodiment 1 in that the dielectric loss layer 3 is a complete and continuous dielectric film, and other structures, materials, and dimensions are the same as those of the embodiment 1, which will not be described in detail here.

[0055] Figure 7 The absorption spectrum of the narrow-band infrared absorber based on the all-dielectric metasurface provided according to the second embodiment of the present invention is shown.

[0056] like Figure 7 As shown, the finite difference time domain method is used to perform numerical simulation calculations on the narrow-band infrared absorber based on the all-dielectric metasurface in Example 2, and the following conclusions are obtained: at the mid-infrared band with a wavelength of 6.612 microns, the absorption rate of the present invention is 79.08%, the bandwidth is 4.27nm, and the quality factor is 1551. Based on the above data analysis, the present invention is effective and superior.

[0057] Embodiment three:

[0058] The structural difference from the first embodiment is that the dielectric resonator 4 - 1 is enlarged by 1.08 times, that is, the diameter of the germanium cylinder is 2160nm, the height is 4730nm, and the period is 3650nm.

[0059] Figure 8 The absorption spectrum of the narrow-band infrared absorber based on the all-dielectric metasurface provided according to the third embodiment of the present invention is shown.

[0060] like Figure 8 As shown, the finite difference time domain method is used to perform numerical simulation calculations on the narrow-band infrared absorber based on the all-dielectric metasurface in Example 3, and the following conclusions are obtained: at the mid-infrared band with a wavelength of 7.286 microns, the absorption rate of the present invention is 82.30%, the bandwidth is 1.98nm, and the quality factor is 3680. Based on the above data analysis, the present invention has effectiveness and superiority.

[0061] The verification of Example 1, Example 2 and Example 3 fully demonstrates the effectiveness and superiority of the present invention. The present invention will have broad application prospects in the fields of food safety, environmental monitoring, biosensing and instant detection.

[0062] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0063] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A narrow-band infrared absorber based on an all-dielectric metasurface, characterized in that: include: substrate; A dielectric base layer, which is disposed on the substrate; A dielectric loss layer, which is arranged on the dielectric base layer; a dielectric resonator array, which is arranged on the dielectric loss layer; The dielectric resonator array includes N dielectric resonators arranged in a periodic manner, wherein N is a positive integer, and the dielectric resonator is a microstructure; The loss rate of the mid-infrared band in the dielectric base layer or the dielectric resonator array is smaller than the loss rate in the dielectric loss layer; The refractive index of the dielectric substrate in the mid-infrared band is smaller than the refractive index of the dielectric resonator in the mid-infrared band.

2. The narrow-band infrared absorber based on the all-dielectric metasurface according to claim 1, characterized in that: The substrate is a silicon wafer or a quartz wafer.

3. The narrow-band infrared absorber based on the all-dielectric metasurface according to claim 1, characterized in that: The material used for the dielectric base layer is calcium fluoride or magnesium fluoride, and the thickness thereof is 1000-100000nm.

4. The narrow-band infrared absorber based on the all-dielectric metasurface according to claim 1, characterized in that: The dielectric loss layer is made of a material that allows a non-zero loss rate in the mid-infrared band, and has a thickness of 50 to 500 nm.

5. The narrow-band infrared absorber based on the all-dielectric metasurface according to claim 4, characterized in that: The dielectric loss layer is a patterned dielectric film or a complete and continuous dielectric film.

6. The narrow-band infrared absorber based on the all-dielectric metasurface according to claim 1, characterized in that: The material used for the dielectric resonator is germanium, and its thickness is 100-10000nm.

7. The narrow-band infrared absorber based on the all-dielectric metasurface according to claim 6, characterized in that: The dielectric resonator is a cylindrical, cubic or polygonal microstructure.

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