Measurement of the facet modal reflectivity spectrum in high quality semiconductor traveling wave amplifiers

We demonstrate that the Hakki-Paoli technique, commonly used for measuring single pass gain in semiconductor lasers, can be modified to measure facet modal reflectivity down to 10/sup -6/ in semiconductor laser amplifiers. We also introduce a new technique based on Fourier and Hilbert transformations of the spontaneous emission spectrum (the SET method) which enhances the signal-to-noise ratio and permits modal reflectivity measurements down to 10/sup -1/.<
>