A 250 Hz spectral linewidth 1.5 mu m MQW-DFB laser diode with negative-electrical-feedback

Abstract
A 1.5 mu m corrugation-pitch-modulated MQW-DFB laser diode (LD) with multielectrodes was frequency stabilized using the negative electrical feedback technique. The FM response of the LD was precisely measured and used for the feedback loop design. The FM noise of the LD was reduced and reached 10 Hz/sup 2//Hz at 1 kHz<or=f<or=10 kHz where f is the Fourier frequency, and the resulting spectral linewidth was 250 Hz, which was mainly limited by the IM noise in the lower Fourier frequency range. The controlled power concentration ratio was 99%.