Origin of optical losses in gallium arsenide disk whispering gallery resonators

Abstract

Whispering gallery modes in GaAs disk resonators reach half a million of optical quality factor. These high Qs remain still well below the ultimate design limit set by bending losses. Here we investigate the origin of residual optical dissipation in these devices. A Transmission Electron Microscope analysis is combined with an improved Volume Current Method to precisely quantify optical scattering losses by roughness and waviness of the structures, and gauge their importance relative to intrinsic material and radiation losses. The analysis also provides a qualitative description of the surface reconstruction layer, whose optical absorption is then revealed by comparing spectroscopy experiments in air and in different liquids. Other linear and nonlinear optical loss channels in the disks are evaluated likewise. Routes are given to further improve the performances of these miniature GaAs cavities.

High frequency optomechanical disk resonators in III–V ternary semiconductors

“…The loaded optical quality factor (Q opt ) evolves between 2 × 10 3 and 6 × 10 4 , with the best intrinsic Q opt attaining 10 5 . While a complete study of optical dissipation [17] was not yet carried on our InGaP disks, our current understanding is that such Q opt may be increased by improving the fabrication procedure, as the material loss sits well below the here-observed level [18]. The drop of Q factor observed in Fig.…”

“…The latter fact permits the production of heteroepitaxial materials with designed photon/phonon interactions, based for example on quantum wells [15]. Together with Si, GaAs is probably amongst the most mature materials in semiconductor technology but both suffer from two photon absorption (TPA) at the telecom wavelength [16,17]. At large optical power, such multi-photon absorption processes dominate optical dissipation and degrade the attainable cooperativity in the widely used linearized regime of optomechanics.…”

Microscopic Nanomechanical Dissipation in Gallium Arsenide Resonators

“…The obtained level of agreement sheds light on the microscopic nature of dissipation. The mechanical damping up to 100 K is well explained by an amorphous TLS model, which suggests a role of the surface reconstruction layer, whose amorphous nature was observed by transmission electron microscopy [39]. In order to model the dissipa-tion at higher T, the single defect model must however be used on top.…”

Theoretical framework for thin film superfluid optomechanics: towards the quantum regime

“…Finally we briefly address the potential of micrometer-sized WGM resonators made of high refractive index semiconductors such as silicon [29,52] or gallium arsenide [5,53] for thin-film superfluid optomechanics. The optimal resonator thicknesses given in figure 2(d) are chosen to maximize the WGM deconfinement, resulting in low WGM effective indices, and therefore do not lend themselves to wavelength-sized radii without incurring significant bending losses [54]. For this reason we consider thicker more confining disks for this application, such as 200 nm thickness for TE modes [53].…”