The Research Of Design Of Long Wavelength Infrared Matasurface Absorber Based On Sandwich Structure

The plasma metasurface is a special artificial electromagnetic material with the ability to perform highly diverse manipulation of incident light at the nanoscale levels.In recent years,the plasma metasurface has attracted extensive attention and research heat due to its powerful light field control capability,and has played a huge role in communications,defense and energy.In many applications of plasma metasurface,broadband metasurface absorber is one of the important research directions,and the use of broadband metasurface absorbers for uncooled infrared detectors not only has better absorption performance,but also is easier to meet the needs of integration of infrared detectors.In this paper,based on the design of long-wave infrared broadband metasurface absorber,a broadband high-absorption structure for uncooled infrared detectors is fabricated.The micro-bridge structure of infrared detectors is fabricated by micro-nanofabrication technology and integrated with the metasurface absorber,so as to improve the absorption of infrared radiation in the broadband range of infrared detectors.The main research results and contents are as follows:(1)A long-wave infrared absorber based on metal-insulator-metal(MIM)sandwich structure with selective wavelength and ultra-thin structure is proposed.The structure consists of graphical metal-insulator pairs.The MIM-structured metamaterial absorber can be seen as a resonator blocked by magnetic field walls,which can strongly couple the energy of electromagnetic wave into the cavity mode,thus enhancing absorption.Because the absorption principle of metamaterial absorber is based on the surface plasmon resonance effect of nanostructure,perfect absorption only occurs at the specific wavelength of plasmon resonance excitation,and its narrowband absorption characteristics seriously hinder its potential application.In order to achieve broadband high absorption,the most direct method is to integrate multiple sub-unit structures to form a super-pixel.By flexibly combining metal-insulator pairs of different sizes,a broadband high absorption structure can be obtained in the long-wave infrared band.The average absorptivity of the proposed structure is over 90% in the range of 6.3-14.8 um.Compared with other narrowband absorption structures with complex patterns in the long-wave infrared band,the proposed structure has the advantages of wide absorption band,high absorptivity and easy fabrication.(2)A novel ultra-wideband,polarization-independent,wide-angle metasurface absorber in long-wave infrared is proposed,in which the MIM cavity is embedded in a bulk dielectric disk.In the long-wavelength infrared region,the hybridized modes generated by the combination of the dielectric-loaded surface plasmon waveguide and the resonant cavity and the PSP mode excitation are the main reasons for the formation of broadband high absorption.The structure has an average absorptivity greater than 94% in the range of 8 ?m to 16 ?m and an average absorptivity greater than 95% in the entire LWIR band(8-14 ?m).Compared with the traditional MIM structure similar to the structure,the absorption performance of the structure has been greatly improved.In addition,the absorptivity of 11.22-12.46 and 13.26-14.59 ?m bands is nearly perfect(over 99%).The results show that the resonant wavelength and working bandwidth can be flexibly adjusted by changing the relevant geometric parameters.This work provides a reference for the design of tunable broadband long-wave infrared metasurface absorbers.The design method can be extended to other bands such as medium-wave infrared band and very long-wavelength infrared band.(3)The preparation of multi-layer uncooled infrared detectors by MEMS process: A process flow for fabricating uncooled infrared detectors micro-bridge structure was designed and fabricated by micro-nano fabrication process.Integrating broadband metasurface absorber structure into the micro-bridge structure can significantly improve the absorption of infrared radiation and improve the performance of the detector.This process is easy to control the size of micro-nano structure,and can realize the monolithic integration of micro-bridge structure and bottom readout circuit.