Study Of Near-infrared All-dielectric Metasurface Absorber Based On Mie Resonance

Metasurface,a kind of metamaterial with the thickness of sub-wavelength,has excellent light-field regulation characteristics,and it can modify the phase,amplitude and polarization state of incident light.The metasurface has the advantages of small size and high integration degree.In the early stage,the metasurface absorber is usually made of metal materials.The absorption characteristics of single band or multi-band can be obtained by designing different metal structures.However,metal materials are incompatible with CMOS technology,and the absorption area of device is mostly located in metal materials,which limits its further application.For the current sensors and detection device in near-infrared region,the responsivity is an important performance indicator.Some researchers pointed out that the free carrier absorption effect of doped silicon material can greatly improve the responsivity of the hot carrier photodetector.In addition,the metasurface absorber made of silicon and other dielectric materials have the advantages of compatibility with the CMOS technology and good heat insulation performance.It can be directly applied in the hot carrier detectors.Based on the theories of metasurface design and Mie resonance occurred in dielectric particles,two kinds of all dielectric metasurface absorbers are designed for the application of near infrared hot carrier photodetector.They can achieve double band and broadband absorption in the near-infrared band,respectively.Performance tests and/or principle analysis are carried on.The main content and results present in the thesis are listed as following:1.Demonstrate a dual-band metasurface absorber that works in the near-infrared region.In order to enhance the absorption of the device,the silicon of the SOI top layer is heavily doped,and the nanoporous metasurface arrays are fabricated.Firstly,the simulation model is established with FDTD numerical simulation software to disclose the influence of the parameters such as the radius and period of the nanohole on the performance of the device,and the fabrication of the metasurface absorber is completed.Then,the performance experiment of the device is carried out.The measured results show that the device has two absorption peaks in the wavelength range from 1500 nm to 1600 nm,whose wavelengths are ?₀=1526.1 nm and ?₁=1554.6 nm,and absorbances are 64.4% and 38.6%,respectively.It is found that the experimental results agree nicely with the simulation results.Finally,we use the multipole decomposition method to analyze the absorption principle of the device,and find that the magnetic dipole resonance mainly exists in the two Mie resonance modes and has the main contribution to the enhanced optical absorption.2.Design the structure of a broadband metasurface absorber that works in the near-infrared region.The silicon of the SOI top layer is heavily doped with P-type ions,and then the elliptical nanopore arrays are designed on the layer.Taking into account the effect of mode coupling on the absorbance of the device,a Bragg reflector is added between the silicon substrate and the buried oxide layer.It is found that when the electric field of the incident plane wave polarizes along the angular bisector of the major axis and minor axis of the elliptical hole,a broadband absorption peak will be generated by the coupling of four narrow-band absorption peaks.The simulation results show that the absorbance of the four narrow-band peaks are 78.3%,81.2%,80.7%and 79.8%,respectively.A broadband absorption spectrum with a full width at half maximum of 40.12 nm is obtained at the center wavelength of 1555.36 nm.