05 Septembre – Thesis defense - Roberto Mostallino

13 h30 Auditorium - 1, avenue Augustin Fresnel (Palaiseau)

Development of DFB high-power laser diodes emitting at 975nm with high wall-plug efficiency for pumping of doped fibers and realization of fiber lasers.

This "CIFRE" PhD addresses the development of DFB high-power Laser diodes, emitting at 975nm with high wall-plug efficiency for optical pumping of doped fibers and realization of fiber Lasers. The thesis was developed in the framework of a close partnership between IMS Laboratory, III-V Lab, one of the main French founders of III-V semiconductor components for electronic and photonic applications and THALES Research & Technology (TRT). An important work of characterization and analysis focused on thermal aspects that contribute, in particular, to limit dramatically the output optical power levels. In this context, we performed a set of complementary characterizations at III-V Lab and IMS allowing us to propose feedback solutions for technological optimization regarding the etching depth and the nature of the thermal heatsink. These solutions were proposed based on physical modeling using a dedicated simulator, that is a property of III-V Lab and FEM simulations of the final microassembled structure. This work has been extended by the fabrication and electro-optical and thermal characterizations of the DFB Laser diodes (wavelength stabilization). An optical power of 8W (CW regime) with an efficiency of 60% has been obtained. Such performances are consistent with the state-of-the-art, especially those published by the Ferdinand-Braun Institute (FBH) in Berlin. The quality of the work carried out in this thesis allowed us to have access to a European LaserLab Cluster grant, to perform additional experiments at the Max-Born-Institute (Berlin) in the group of Prof. J. TOMM in 2017. These works have addressed time-resolved thermal characterizations of these high-power symmetrical (LOC, SLOC) and asymmetric (AOC) double-heterostructure Laser diodes by using microphotoluminescence, time-resolved photoluminescence, photocurrent spectroscopy and pulsed measurements) and enabling to analyze both residual thermomechanical stress due to the surface mounting process of the bare die onto the submount and COD threshold extraction as a function of the different vertical structures.

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