Coupled-mode analysis of vertically-coupled AlGaAs/AlOx microdisk resonators

Clément Arlotti (1) , Gael Lafleur (1) , Alexandre Larrue (1) , Pierre-François Calmon (2) , Alexandre Arnoult (2) , Guilhem Almuneau (1) , Olivier Gauthier-Lafaye (1) , Stéphane Calvez (1)

1 LAAS-PHOTO - Équipe Photonique
2 LAAS-TEAM - Service Techniques et Équipements Appliqués à la Microélectronique

This article reports the experimental and theoretical assessments of the optical characteristics of recently-introduced vertically-coupled microdisk resonators made by selective oxidation of AlGaAs multilayer structures. Experimental measurements show that the Q-factors are in the 10 3 to 10 4 range for diameters ranging from 75 to 300 µm. To establish the origins of this limited performance a coupled-mode-theory-based model of the single-access-waveguide-coupled resonator system was developed. It includes features which are specific to oxide-based vertically-coupled resonators, namely losses towards the slab waveguide lying under the resonator and a coupling region with an asymmetric and multilayer structure. Setting this simulation tool required the proposal and validation of a general criterion to select an appropriate set of decomposition permittivity profiles to be able to accurately model the characteristics of these more complex couplers using the coupled-mode-theory approach. This theoretical development is generic and can be now deployed to simulate any device which includes multi-waveguide couplers with arbitrary piece-wise-constant profile of the dielectric permittivity. Exploiting this particular development and experimental measurements of the disk sidewall roughness and of the coupling lengths, the calculated and experimental Q-factors are found to be in good agreement and allow establishing that the current performance is limited by the scattering losses and the slab-leakage losses for small-and large-diameter devices respectively.

Mots clés: optical waveguide components; microresonators; integrated optics; coupled-mode analysis

Domaines: Optique [physics.optics]; Optique / photonique; Micro et nanotechnologies/Microélectronique

Clément Arlotti, Gael Lafleur, Alexandre Larrue, Pierre-François Calmon, Alexandre Arnoult, et al.. Coupled-mode analysis of vertically-coupled AlGaAs/AlOx microdisk resonators. IEEE Journal of Quantum Electronics, 2018, 54 (3), ⟨10.1109/JQE.2018.2811739⟩. ⟨hal-01741465⟩