Pulse generation from mode locked VECSELS AT 1.55 um

Overview & Synopsis

In a first step, we have developed and implemented VECSEL structures, aiming at maximizing the laser output power through a proper thermal management. The fabricated VECSEL chips contain an InP-based active region for emission at 1.55 µm. A hybrid metal-GaAs/AlAs Bragg mirror is used to achieve efficient dissipation of the heat generated in the active region. The semiconductor structure is integrated to various host substrates and the VECSEL performances are investigated numerically and experimentally. VECSELs with CVD diamond substrates have the best overall performance and are promising for large output power (> 500 mW), while electroplated copper substrate is demonstrated to be a flexible and cost-effective approach for thermal management in 1.55 µm OP-VECSEL in order to achieve output power of several tens of mW to ~ 200 mW. The second part of the work is devoted to the development of SESAM structures at 1.55 µm. The structures include an active region consisting of InGaAsN / GaAs quantum wells surrounding by GaAsN planes, allowing to achieve absorption relaxation time of few picoseconds. The SESAM microcavity resonance was adjusted via a selective etching of phase layers specifically designed to control the magnitude of both the modulation depth and the intra cavity group delay dispersion of the device.Finally, assembling VECSEL and SESAM chips in a cavity, we observe experimentally that the mode-locked pulse duration could be reduced from several picoseconds to less than one picosecond when the resonance and group delay dispersion of the SESAM microcavity are tuned.