Study On The Design And Optical Properties Of Plasmonic Metamaterial Absorbers

Surface Plasmons?SPs?are free electrons on the metal surface to oscillate when incident light irradiates the interface between the metal and the medium.When the frequency of incident light is close to the frequency of free electron oscillation,the phenomenon of plasmon resonance will occur.Due to the characteristics of the localized SPs field,the diffraction limit of the light field in the spatial domain is broken.Based on the strong field enhancement effect,SPs have been widely used in perfect absorbers and optoelectronic devices.Based on the novel properties of surface plasmons in metal nanostructures,high-performance perfect absorbers can be designed.This thesis is to use the finite-difference time-domain method to numerically calculate the proposed perfect absorber and study its optical properties.The main contents are as follows:1.The theory and application of surface plasmons are briefly introduced.Finite-Difference Time-Domain Method?FDTD?and Finite Element Method?FEM?are introduced in detail.In this paper,we use the finite-difference time-domain method to numerically simulate the proposed perfect absorber and study its optical properties.2.An ultra-wideband perfect absorber is designed via the silica-chromium-silica-titanium?SiO₂-Cr-SiO₂-Ti?four-layer structure.The spectral bandwidth can achieve 2350 nm with the absorption over 90%.The absorption window ranges from 1022 nm to 3372 nm.The average absorption rate is 93.9%and the maximum absorption is up to 99.6%.In addition,the physical mechanism of the absorber is also studied.3.A truncated Ti and Si cones metasurface has been proposed for wide-band solar absorber,which produced a high average absorption of 94.7%in the spectral region from 500 to 4000 nm.With taking the absorption over 90%into account,the spectral range is varied from 0.5?m to 3.552?m,suggesting a perfect absorption bandwidth up to 3.052?m.The maximal absorption is up to 99.8%.These excellent absorption properties show great improvement both on the absorption bandwidth and absorption efficiency than the common noble metallic nano-resonators based absorbers.These properties pave a new way for achieving full-spectrum solar absorption via combining the Ti material and semiconductors.4.A new ultra-thin silicon film perfect absorber is proposed.the proposed perfect absorber consists of a ultra-thin silicon film sandwiched by the top metal resonant metasurface and the bottom metal film substrate.In this work,Si and Au films are obtained via a physical sputtering deposition process.The formation of the Au resonators metasurfaces are based on the moderate heat-treatment.In addition,the optical properties of the absorber were also studied.5.An absorber is proposed for achieving broadband perfect absorption in the full visible light range.The absorber is formed by the TiO₂/TiN dual-layer nano-grating on the thick TiN film substrate.The spectral absorption average efficiency is up to94%in the wavelengths from 380 nm to 760 nm?visible light?.The full-spectrum visible light absorption is observed to be maintained in a wide angle range under the oblique illumination.The high absorption is also retained under different polarization states.Moreover,the absorber has highly thermal stability.These findings pave new insights on the refractory perfect visible light absorber for nano-scale photo-thermal process,microfluid thermal disinfect or local high-temperature process,etc.6.A low-cost,short-time,and easy-to-operate Polydimethylsiloxane?PDMS?mold preparation experiment is proposed.The PDMS mold perfectly replicates the surface structure of rose petals.The PDMS mixed solution is poured on the surface of rose petals,and a series of operations such as water bath ultrasonic,vacuum degassing and heating are used to prepare the PDMS mold.