Characterization of the hybrid integration of a shared dispersive element laser and a modulator

This paper characterizes a ten-channel waveguide grating router multifreque ncy laser (MFL) with 200-GHz channel spacing coupled to a 2,5-Gb/s electroa bsorption modulator on a separate chip. We show theoretically and experimen tally that in long-cavity semiconductor lasers such as the MFL, light refle cted back into the laser perturbs the device wavelength a negligible amount compared to the inherent modulator dynamic chirp hut can cause multimode l asing, However, if the ratio of the net external reflectivity to the laser facet reflectivity is kept below approximately 1/( 4 alpha(2) +1) where alp ha is the linewidth enhancement parameter in the laser, the lasing spectrum is immune to the back-reflected light. We also show that placing a simple "isolator" that only has to rotate the polarization of the back-reflected l ight rather than provide full isolation can easily provide the immunity.