Integrated laser Mach-Zehnder modulator on indium phosphide free of modulated-feedback

Abstract

The main problem of integrated laser/Mach-Zehnder modulators is the modulated feedback due to reflections on the output multimode image (MMI). We have solved this problem changing the modulator technology from "deep-ridge" to "shallow-ridge" technology. In that case, the index step seen by the light in the MMI is far lower, then reflections which are nondetectable in optical low coherence reflectometry (OLCR) and there is no laser resonance left. This technology also enables a wider bandwidth (thanks to a stronger electrooptic effect) and a higher output power (better coupling between laser and modulator and lower loss of shallow-ridge guides).