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Friday 5th of february 2021, 9:15 am, INSA Rennes

Alejandro LORENZO RUIZ defends his PhD thesis

« Nonlinear integrated photonic devices based on gallium phosphide »

Integrated photonics ; nonlinear photonics ; photonic circuits ; microresonators


The objective of this thesis is to investigate different aspects of nonlinear integrated devices based on GaP material, focusing on two processes : the use of GaP microdisks to perform second harmonic generation in the near infrared regime using whispering gallery modes and the use of IR waves to produce THz using difference frequency generation.
First, we study the vertical evanescent coupling process to a GaP microdisk to address its impact on the efficiency of the nonlinear device and demonstrate the importance of propagation constant mismatched couplers to properly design fully encapsulated devices.
We also demonstrate that the origin of the specific phase matching selection rules in circular microresonators is due to the Berry phase experienced by the transverse spin angular momentum components of the WGMs into azimuthal momentum.
To fabricate the designed schemes, we investigated the technological challenges of the process flow for the fabrication of these GaP-based photonic circuits, focusing on three processes : bonding, lithography, and encapsulation.
Finally, we propose a novel approach for integrated THz generation in the Reststrahlen band. Using surface phonon polariton modes to guide THz waves and showing how an unusual crystal alignment is suited for this configuration we estimate efficiencies about the state-of-the-art level.

Committee members
Christelle MONAT Professor, INL, Ecole Centrale de LyonExaminator
Mathieu CHAUVET Professor, Femto-ST, Université de Franche-ComtéExaminator
Sophie BOUCHOULE Director of research, C2N, CNRSMember
François LÉO Researcher, OPERA, Université Libre de BruxellesMember
Alexandre BECK Assistant Professor, Institut Foton, INSA de Rennes PhD Manager
Yoan LÉGER Researcher, Institut Foton, CNRSPhD Manager
Charles CORNET Professor, Institut Foton, INSA de RennesPhD Supervisor