Study Of Metasurface Optical Absorbers Based On Surface Plasmon Polaritons

Surface plasmon based metasurface absorbers are an important way of achieving perfect absorption.Surface plasmon polaritons have the capability of limiting electromagnetic waves within a subwavelength distance,and thus lead to high localized field amplification,which provides an opportunity for miniaturization of optical devices.Metasurface is a special kind of metastructure,which often exhibits periodical structure along a plane,while retaining structural parameters of wavelength or subwavelength magnitude on the normal direction.For these reasons,metsurfacce structure devices are highly scalable along the plane,making it applicable for various sizes of surfaces.This thesis aims to study the application of surface plasmon polaritons and metasurface structures in the design of optical absorbers,and proposes an ultra-wide band,an ultra-narrow band,and a tunable absorber structure,achieving high performance absorption.The contents of this study are as follow:1、Design of a quadruple staircase absorber,which achieves an average absorption of 98.74%within the range of 300 nm to 2000 nm wavelength.At AM1.5 sunlight,its solar absorptivity can reach 98.7%,offering a photothermal conversion efficiency of 95.6%at room temperature.By varying the structural parameters,the design can be further made to absorb over a 200 nm to 3000 nm wavelength band.2、Dual gold plate periodical structure realizing an ultra-narrow band absorption of 3.85 nm full width at half maximum.The single absorption peak of 99.97%locates at 1582.44 nm.Due to the simplicity of the structural design,the position of the peak can be linearly adjusted by a single parameter.Meanwhile,the device is insensitive to the ambient refractive index,and the peak only has a 0.37 nm redshift while the surrounding refractive index goes from 1 to 2,showing great stability against the environment.3、Temperature tunable absorber based on the phase change property of vanadium dioxide.Below the phase change temperature,the absorber has three absorption band over 90%,599 nm to 1531 nm,2958 nmto 3895 nm,4183 nm to 4430 nm,respectively;above the temperature,bands at mid-infrared subside,only the band from 599 nm to 1855 nm remains.