احمد محمدی اسلامی

Generalized multipole technique (GMT) has been implemented as a powerful and precise method for investigating the interaction between radiation field and matter on a scale under the diffraction limit. GMT, Mie and generalized Mie codes have been developed in MATLAB. To validate the GMT code, both analytical solvers namely, Mie and generalized Mie have been performed for simulating scattered field from dielectric microcylinders and plasmonic nanoantenns. The excellent agreement between all techniques demonstrates high precision of GMT method for computational nano-optics analysis. In the next step, the effect of different physical parameters such as material, size, geometry and the refractive index of background media on optical properties of nanoantennas have been analyzed. It is turned out that one can control the spectral position of localized surface plasmon resounance modes and coupling resonaunce modes according to spectral region of solar cell operation. In this work, genetic algorithm (GA) has been investigated as a method which is well suited for the task of optimizing plasmonic structures and optical thin-film coatings. GA code is developed in MATLAB, as well. Coupled nanoantennas resonate scattered field in the coupling mode, thus, we focus on optimizing radius and surface to surface distance of an Ag coupled nanoantenna embded in chrystalline silicon background in a way that total absorption enhances inside the active material in near IR. Bulk and nanostructured antireflection coatins (ARCs) are introduced as efficient structures for increasing photocurrent density in silicon solar cells. Last but not the least, optical thickness of ARC are optimized using GA, so that the reflection from layers over all visible spectrum range and incident angles 0 to 60 degrees are minimum.