Vertically Coupled Microdisk Resonators Using AlGaAs/AlOx Technology

Abstract

In this letter, we report the first experimental demonstration of microdisk resonators that are vertically coupled to their buried access waveguides on III-V semiconductor epitaxial structures using an original fabrication process. The here-proposed and validated three-dimensional integration scheme exploits selective lateral thermal oxidation of aluminiumrich AlGaAs layers. Compared with the previously reported processing techniques, this new scheme is simpler as it does not require any planarization or substrate transfer steps. As a proofof-principle demonstration of this approach, 250-µm diameter microdisk devices exhibiting quality factor reaching ∼8500 have been successfully fabricated.

Coupled mode analysis of micro-disk resonators with an asymmetric-index-profile coupling region

“…of SPIE Volume 10090 -article 10090-48 The structure under investigation is the one we recently demonstrated 11 and its vertical index profile in the coupling region is depicted in figure 1. Our criterion to select the permittivity decomposition applies to coupler structures with piece-wise constant overall permittivity distributions , as represented in figure 2.…”

“…In this section, we investigate the coupled microdisk characteristics of the recently-reported and above-described vertically-coupled structure 11 . The microdisk diameter is taken to be 300 µm and the coupler length is varied to simulate various guide-to-resonator offsets.…”

“…We subsequently exploit the derived mode-overlap coefficients and loss rate as basic building blocks of the transfer function (11) to evaluate the theoretical transmission characteristics of the coupled resonator as function of wavelength and as function of the coupling length L.…”

Coupled-Mode Analysis of Vertically Coupled AlGaAs/AlOx Microdisk Resonators

“…The second method uses a substrate transfer to be able to etch waveguides on both sides of a membrane structure [12]. The third technique exploits a localized oxidation to define the buried waveguide structure underneath the etched resonator [13] [14]. The relative complexity associated with the above-described fabrication procedures has somewhat hindered the general uptake of the vertical integration scheme.…”

“…In this paper, following our recent extension of the use of selective lateral oxidation [19][20] to create vertically-coupled microdisk resonators on an (Al)GaAs platform [14], we provide a more extensive set of experimental characterization results. Additionally, the device performances are quantitatively analyzed using a CMT-based model taking into account the specificities of this embodiment namely a slab-waveguide loss channel and an asymmetric multi-layer separation between the access and resonator waveguides.…”