Interferometric measurement of time-varying longitudinal cavity modes in GaAs diode lasers

Measurement of mode chirping in a current-modulated semiconductor laser was performed using a Michelson interferometer. For a current step excitation, the rate of this chirping decays as a function of time, and two characteristic time constants were identified. Their interpretation is discussed, and the thermal impedance of the device is calculated. In addition, the significance of such a measurement for the analysis of chirp-induced modal noise in optical fibers is discussed, and experimental results are presented.