Estimation of angle-dependent mode coupling and attenuation in step-index plastic optical fibers from impulse responses.

We report on a method for estimation of angle-dependent mode coupling and attenuation in step-index plastic optical fibers (SI-POFs) from the shapes of impulse responses at two different fiber lengths. While alternating the fiber lengths, deviations between simulated and reference impulse responses are minimized by optimizing both mode coupling and attenuation parameters using pattern-search routines. Applying a matrix-based finite-difference approach to Gloge's time-dependent power flow equation fast computation of simulated impulse responses is enabled.

Micro-spectroscopy on silicon wafers and solar cells.

Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the doping density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole density-dependent Fano resonances of the first order Raman peak.

Illumination-induced errors associated with suns-V(OC) measurements of silicon solar cells.

I(SC)-V(OC) curves measured by the suns-V(OC) method are widely used for solar cell characterization due to its being unaffected by series resistance effects. A common setup for this measurement system uses a xenon photoflash for illumination purposes, resulting in a fast acquisition of the suns-V(OC) measurement data during the decaying edge of one flash. However, the use of a xenon photoflash accompanies also several disadvantages.