MEASUREMENT OF THE FACET MODAL REFLECTIVITY SPECTRUM IN HIGH-QUALITY SEMICONDUCTOR TRAVELING-WAVE AMPLIFIERS

We demonstrate that the Hakki-Paoli technique, commonly used for measu ring single pass gain in semiconductor lasers, can be modified to meas ure facet modal reflectivity down to 10(-6) in semiconductor laser amp lifiers. We also introduce a new technique based on Fourier and Hilber t transformations of the spontaneous emission spectrum (the SET method ) which enhances the signal-to-noise ratio and permits modal reflectiv ity measurements down to 10(-7).