Prediction of the gain versus injection-current characteristic of individual semiconductor laser amplifiers

A method of calculating the gain versus current characteristic of an individual laser amplifier is presented. The method applies to traveling-wave amplifiers that are derived from semiconductor lasers by antireflectively coating both facets. It relies on a knowledge of certain general parameters, the power versus current characteristics of the laser before and after the first coating has been applied, and a measurement of the residual reflectivity of the first coating. These measurements are normally done during the coating process and therefore require no additional experimental effort. It is found that four parameters, along with a set of fixed general parameters, are sufficient to provide good agreement between calculated and measured results for different lasers