Search

Building integrated semitransparent thin-film solar cells is a strategy for future eco-friendly power generation. Organic photovoltaics in combination with dielectric mirrors (DMs) are a potential candidate as they promise high efficiencies in parallel to the possibility to adjust the color and thus the transparency of the whole device. A fully solution processed and printable DM with an easily adjustable reflection maximum is presented that can be facilely attached to solar cells. The DM is optimized via optical simulations to the particular needs of the device with regard to photocurrent enhancement. The excellent agreement between experimental and theoretical results confirms the high optical quality of the printed layers with respect to homogeneity and surface roughness. The used inks are organic–inorganic nanocomposites with a large refractive index contrast of ≈0.7. The short-circuit current is enhanced by up to ≈24% for a semitransparent polymer solar cell.

A stable iterative solver for the simulation of optical waves in metals using finite difference frequency domain (FDFD) method is presented. The corresponding discretization of Maxwell's equations enables simulating electromagnetic waves in structures when materials with negative permittivity are involved. Convergence of the iterative solver is proved for positive and negative permittivities. Numerical results are presented for a thin-film silicon solar cell structure containing silver back contact.

The thermal lensing effect in the crystal influences the stability of solid-state lasers. The deformation of the end faces of the crystal and the temperature dependence of the refraction index causes this effect. The photoelastic effect produced by thermal induced stress in the crystal has also an influence. For high power lasers and for lasers with a radially polarized laser beam the analysis of the photoelastic effect is important. We use FE model to calculate the deformation, heat and stress distribution in the laser crystal with high accuracy in this work. Using the calculated stress distribution we also simulated the refraction index anisotropy with respect to the crystal orientation. We can study stability of laser resonators for both radially and azimuthally polarized laser beam, as a result of our simulation. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

The difficulties of solving initial-value solid-state laser problems numerically arise from both stiffness of the problems and near-to-zero nonnegative exact solutions. Stability and non-negativity must be maintained simultaneously in the numerical solutions. Backward differentiation formulas (BDFs) is capable of dealing with stiff problems ,but is of small oscillation when time-step is large. Therefore unfortunately BDFs suffers from severe time-step restriction . In this paper,we present an optimized numerical approach, with which 3-dimensional laser problems can be solved faster and much more efficiently. These techniques can not only be used for solid-state laser systems, but can also be applied to solve other stiff problems which have near-to-zero nonnegative exact solutions. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper we analyze the approximation properties of Trigonometric Finite Wave Elements (TFWE). These Finite Ele- ments were developed for solving Helmholtz equation and Schrodinger equation with respect to special applications, e.g. for simulating resonators with internal reflections occurring in Distributed Feedback (DFB) lasers and other laser types. We emphasize the advantages of the TFWE in comparison to standard bilinear Finite Elements (FE).

Automatic grid generation is very important in industrial applications. Furthermore, in several applications discretization grids are needed which provide an anisotropic refinement and an accurate approximation of the derivatives of the solution. These requirements are fulfilled by semi-unstructured grids. In this paper, we report how semi-unstructured grids are used in the laser simulation program LASCAD [3].