On the characteristic lengths in the variable stripe length method for optical gain measurements

Although the variable stripe length (VSL) method has been widely used to measure the optical gain in thin film active media, different nor totally rigorous criteria have yet been used to estimate two important characterization parameters, namely, threshold and saturation lengths, on which the method critically depends. Here we present a formalism which leads to analytical expressions to rigorously calculate these characteristic lengths from VSL data, providing a unique criterion for the estimation of the amplified spontaneous emission threshold and saturation points. (C) 2010 Optical Society of America