Research On The Performance Of Wideband Absorbere Based On Finite-Difference Timedomain Method

With the development of nanophotonics,today's surface plasmon resonance(SPR)broadband absorbers based on finite time domain difference methods have attracted more and more researchers'scientific interest because of their excellent electromagnetic properties.Ultra-wideband perfect absorber in a specific frequency band of sunlight can be highly concentrated light field intensity,to achieve ultra-wideband perfect absorption,due to its small size,high integration,low cost,has been widely used in photothermal conversion,seawater desalination and other fields.Through a large number of theoretical calculations and experimental studies,it is found that the bandwidth,amplitude and resonance wavelength of the light absorption structure design are related to the material,medium and shape size of the structural metal particles.Therefore,this paper mainly focuses on a series of research work around the finite time domain difference method and the construction of a perfect broadband absorber.The main research contents of the thesis are as follows:(1)A molybdenum disulfide(Mo S₂)spherical absorber was designed based on the numerical simulation of the finite time domain difference method.The absorber calculated the optimal structural parameters and absorption performance,and analyzed the surface plasmon resonance according to the electromagnetic field distribution.In principle,under the coupling effect of SPR and LSPR,the absorber has an average absorption rate of 97%and a relative bandwidth of 153%in the light wavelength range of 200 nm to 1500 nm.Through structural analysis,it is found that the composite material of molybdenum disulfide and lanthanum fluoride(La F₃)will give the absorber a wider absorption bandwidth and higher absorption rate.On the basis of this structure,the molybdenum disulfide sphere was replaced with a sphere of a composite material of molybdenum disulfide and lanthanum fluoride.Through research,it was found that the performance of the absorber composited with molybdenum disulfide and lanthanum fluoride was better than that of the molybdenum disulfide array nanometer The spherical structure absorber was also used to obtain the optimal absorption performance,with an average absorption rate of 98%in the light wavelength range of 200 nm to 2500 nm.(2)A broadband absorber with periodic composite structure based on numerical simulation of finite time-domain difference method is designed.At the same time,the relationship between the absorption performance and structural parameters of the absorber is optimized through calculation.By analyzing the coupling effect between the surface plasmon resonance and the localized surface plasmon resonance(LSPR)of the broadband absorber,on the basis of the coupling effect,an average absorption rate of 95%in the light wavelength range of 200 nm to 2500nm is achieved.The research results show that the absorber proposed in this paper is insensitive to light polarization,has wide-angle characteristics,and is easy to realize recycling.(3)The basic structural composition and detailed operation process of the interface photothermal evaporator are introduced,the evaluation method of its performance is summarized,the absorption performance of the interface photothermal evaporator is discussed in detail by the material selection of the photothermal absorber layer and the microstructure design of the photothermal material,and the preparation process of the photothermal evaporator is specifically discussed,so the interface photothermal evaporator has great application value in the fields of photothermal conversion,seawater desalination,and rapid collection of sea salt.The simulation results show that the three ultra-wideband perfect absorber models designed in this paper have wide band,high absorption and good thermal stability,and are insensitive to light polarization and have wide-angle characteristics.The absorber is applied to the interface photothermal evaporator,a good structural design can make the solar spectrum in the photothermal absorption layer to achieve effective light absorption,therefore,through the structural design of the interface photothermal evaporator to adjust,so that the absorbing area increases,thereby improving its light absorption performance.