Efficient Broadband Absorber Based On Plasmonic Nanoparticles

Absorbing materials, as a kind of functional materials to absorb electromagnetic(EM) wave, has a very wide range of applications in the modern information age. Especially, an efficient broadband absorber plays a crucial role in solar cells, thermophotovoltaic collection systems, etc. In recent years, absorbers based on metal nanoparticles become a research focus due to their high absorptivity and novel absorption mechanisms. In thesis, we propose a kind of a bsorbers based on plasmonic nanoparticles.Here, the traditional narrow band absorber composed of metal-insulator-metal has been replaced by broadband ones comprised of metal-insulator-metal nanoparticles with different sizes, which can excite surface plasmon resonances at in different wavelengths. The absorbing performance of samples with different metal nanoparticles layer(MNL) thicknesses(tm) and different dielectric layer thicknesses(td) were studied. Experimental results show that while td kept unchanged and tm increased, the absorptivity increases first and then decreases, while tm kept unchanged and td increased, the absorption peaks and valleys shift to longer wavelengths. In addition, the influence of base pressure on the absorption performance was studied. The absorptivity at lower base pressure was higher than that at higher base pressures. The optimized absorbing structure was obtained by adjusting tm, td and base pressure. At a lower base pressure, the integrated absorption efficiency of the sample is 93% over the 300 ~ 1100 nm wavelength range when tm = 6 nm and td = 80 nm. Theoretically, we calculate the absorption efficiency of the structure with different MNL thickness by COMSOL. Our calculated absorption spectra is consistent with the experimental results. It is worth mentioning that, the proposed absorber is very promising in practical applications, due to their easy fabrication and good repeatability.This thesis also studied the metal-insulator-metal particle absorbers with different periodicities. Here, we regard metal nanoparticles layers- insulator composite film as one period, the number of periodicities is represented by N. The integrated absorption efficiency of the sample with N = 4 is 90%, and the absorber also angular insensitive. Moreover, the absorption is polarization insensitive at normal incidence.Finally, the summary and outlook are presented.