Abstract

In the last decade, nanotechnology has enormously and rapidly developed. The technological progress has allowed the practical realization of devices that in the past have been studied only from a theoretical point of view. In particular we focus here on nanotechnologies for the optical frequency range, such as plasmonic devices and photonic crystals, which are used in many areas of engineering. Plasmonic noble metal nanoparticles are used in order to improve the photovoltaic solar cell efficiency for their forward scattering and electromagnetic field enhancement properties. Photonic crystals are used for example in low threshold lasers, biosensors and compact optical waveguide. The numerical simulation of complex problems in the field of plasmonics and photonics is cumbersome. The dispersive behavior has to be modeled in an accurate way in order to have a detailed description of the fields. Besides the code parallelization is needed in order to simulate large and realistic problems. Finite Difference Time Domain (FDTD) is the numerical method used for solving the Maxwell's equations and simulating the electromagnetic interaction between the optical radiation and the nanostructures. A modified algorithm for the Drude dispersion is proposed and validated in the case of noble metal nanoparticles. The modified approach is extended to other dispersion models from a theoretical point of view. A parallel FDTD code with a mesh refinement (subgridding) for the more detailed regions has been developed in order to speed up the simulation time. The parallel approach is also needed for the large amount of required memory due to the dimension of the analysis domain. Plasmonic nanostructures of different shapes and dimensions on the front surface of a silicon layer have been simulated. The forward field scattering has been evaluated in order to optimize the concentration of the light inside the active region of the solar cell. Some design parameters have been deduced from this study. Opal photonic crystals with different filling factors have been simulated in order to tune the optical transmittance band-gap and find a theoretical explanation to the experimental evidences.