MEASUREMENT OF 50-FS NONLINEAR GAIN TIME CONSTANT IN SEMICONDUCTOR-LASERS

The symmetric and asymmetric nonlinear gain in 1.3-mu-m semiconductor laser are measured in the frequency domain by a novel pump-probe technique using an external cavity traveling-wave semiconductor ring laser. A very short time constant of about 50 fs is measured as the dominant process. The data also indicated the presence of a smaller contribution approximately 15% of the magnitude of the dominant process and with a long time constant consistent with hot carriers effect.