Narrow linewidth multi-electrode monolithic external cavity DFB laser incorporating a phase modulator giving 2nm continuous tuning

Narrow linewidth, wavelength tunable semiconductor laser diodes are important devices for the practical realization of coherent optical communication systems. Linewidths less than lMHz can be readily obtained with a DFB laser monolithically integrated with an external cavity. However, such devices show periodic linewidth broadening and mode hops with increasing laser current due to variation in the feedback phase, and cannot be tuned while maintaining a narrow linewidth [1]. We report here a novel multi-electrode monolithic external cavity DFB laser incorporating a phase modulator which gives a narrow linewidth for more than 2nm continous tuning.