Modal formulation for diffraction by absorbing photonic crystal slabs

TL;DR

This paper introduces a finite element modal formulation for analyzing diffraction and absorption in complex, absorbing photonic crystal slabs, enabling efficient design optimization for photovoltaic applications.

Contribution

A novel semi-analytic finite element modal approach for diffraction in absorbing photonic crystal slabs of arbitrary geometry is developed, providing physical insight and computational efficiency.

Findings

Validated method on silicon nanowire arrays

Accurately predicts absorption spectra

Identifies optimal array geometries

Abstract

A finite element-based modal formulation of diffraction of a plane wave by an absorbing photonic crystal slab of arbitrary geometry is developed for photovoltaic applications. The semi-analytic approach allows efficient and accurate calculation of the absorption of an array with a complex unit cell. This approach gives direct physical insight into the absorption mechanism in such structures, which can be used to enhance the absorption. The verification and validation of this approach is applied to a silicon nanowire array and the efficiency and accuracy of the method is demonstrated. The method is ideally suited to studying the manner in which spectral properties (e.g., absorption) vary with the thickness of the array, and we demonstrate this with efficient calculations which can identify an optimal geometry.