Light Scattering and Surface Plasmon Resonance on Prism-Metal-Dielectric Coupler

Abstract

Advances in scientific knowledge of plasmonics offer key ideas for nanotechnology applications from biosensors to plasmonic solar cells. For biosensors there are attempts to improve their sensitivity, and for solar cells both their efficiency in energy conversion capability and harnessing by enhancing light-matter interaction, e.g., by designing antireflection surfaces and surface roughing for trapping or absorbing of light. One of the most common models is designed as a dielectric-metal coupler in similar to the Kretschmann's configuration design. In this study, we used COMSOL Multiphysics software implemented with finite element method (FEM) to study the relation of incident angle of light with respect to wavelength, investigate the physical relevant parameters and find the optimal parameters for occurrence of surface plasmon (SP) resonance. In the first part we studied the SiO2-Ag-air coupler to find the optimal thickness of the silver layer. For smooth surface of the Ag-slab, we found that its thickness of 40 nm yields the minimum reflection close to zero with the electromagnetic field of wavelength of 565 nm incident at the angle of surface plasmon resonance of 46°. For the rough surface of grating type, there are dips at other angles than at the angle of surface plasmon resonance. For the second part, we designed the structures of plasmonic solar cell to investigate the physical relevant parameters and the effect of particle shape, size and array pitch on the coupling of light for the plasmonic solar cell, which can be integrated within the solar cell in three configurations. For the first configuration, the spherical silver nanoparticles (Ag) are imbedded at the top as well as the Ag film at the bottom of the solar cell. For the second one, the Ag nano-spheres are embedded inside between the silicon (Si) and SiO2 film. For the last one, the Ag gratings are placed at the bottom face of the plasmonic solar cell. A TM wave with wavelength of 530 nm is incident on the top surface of the first configuration and it was found that the minimum dip in reflection corresponding to the highest absorption occurs at an angle of SP resonance of 36° for the spacing distance between the Ag nano-spheres of 160 nm. For the second and the third configurations where the Ag spheres embedded inside between the Si and SiO2 interface and the Ag grating at the back of the solar cell, the dips in reflection resonance angle of SP resonance occurs at an angle of 74" and 40" with incident wavelengths of 650 nm and 460 nm, respectively. It is found that for various spacing distances of either the Ag nano-sphere or the Ag grating of 150nm, 160nm, 170nm and 180nm there is no change in angle of SP resonance.