FM SUPERMODE OPERATION OF INGAASP SEMICONDUCTOR-LASERS

The multimode operation of InGaAsP semiconductor lasers of the Fabry-Perot type at power levels of a few milliwatts and higher is identified as FM supermode operation. It is shown that the observed phenomena can be explained by the creation of a dynamic gain grating probably related to a dynamic carrier temperature grating. A gain suppression time constant of about 0.3 ps was required to explain the observed FM supermodes. The occurrence of the FM supermodes puts a fundamental limit of about 3 nm on the full spectral width obtained at high powers from the Fabry-Perot-type semiconductor lasers currently used in fibre-optic telecommunication systems.