Ultra-High-Q Racetrack Resonators on Thick SOI Platform Through Hydrogen Annealing Smoothing

Abstract

We implemented a hydrogen annealing based postprocessing technique as a tool to improve the sidewall roughness of 3 μm thick silicon-on-insulator (SOI) waveguides and demonstrated ultra-high-Q factors on racetrack resonators leveraging on the propagation loss reduction achieved through the smoothing process. The designed racetracks are based on a combination of rib waveguides and strip-waveguide-based Euler bends. We measured intrinsic quality factors of 14×10 6 for a racetrack with a footprint of ~5.5 mm 2 and 10.7×10 6 for a smaller racetrack with footprint of ~1.48 mm 2 . The estimated propagation loss for the rib waveguides was ~2.7 dB/m, representing a ×3 reduction respect to the previously measured losses of 3 μm thick SOI rib waveguides treated with thermal oxidation smoothing. Overall, the post-processing technique allowed to significantly reduce the sidewall roughness without altering the geometry of the waveguides, unlike in sub-micron scale SOI platforms, making it an attractive solution for applications demanding ultra-low losses.

Supporting quantum technologies with an ultralow-loss silicon photonics platform

“…5(c), 6(a), and 6(b). This way, tight bends with loss lower than 0.02 dB can be achieved with effective bending radii of a few tens of microns, enabling, e.g., compact race track resonators with quality factor Q of up to 14 million 9 , 12 …”

“…We have demonstrated several different types of wavelength filters, including ring resonators with Q up to 14 million, 9 , 12 compact MMI resonators, 43 flat-top lattice filters, 44 and flat-top ring-loaded MZIs 45 . Some of these filters can be designed to have <0.5 dB excess loss.…”

“… – 6 In this regard, the micron-scale silicon photonics platform 7 brings with it a unique set of properties and building blocks. This includes low propagation losses (down to 3 dB/m demonstrated to date 8 , 9 ), broadband and low-loss coupling to fibers (≈0.5 dB), fast (>40 GHz) and responsive (≈1 A/W) integrated germanium photodetectors, 10 upreflecting mirrors (URM) for broadband and low-loss coupling to arrays of detectors, tight bends 11 enabling high-integration density, efficient phase shifters, low-loss Mach–Zehnder interferometers, multimillion Q ring resonators, 9 , 12 polarization insensitive operation, and polarization splitters 13 and rotators, including all-silicon Faraday rotators (FRs) 14 …”

Robust high-Q quasi-BICs in double-layer high-contrast metagrating with temperature self-compensation for refractive index sensing

“…silicon-based high-contrast gratings offer a novel route for optical sensing owing to their high reflectivity over a broad spectrum, sensitive optical resonances and compatibility with the complementary metal oxide semiconductor (CMOS) technology [14][15][16]. However, as the inherent thermo-optic (TO) effect of silicon (Si), the resonance wavelength of silicon-based sensors is very sensitive to temperature variations.…”

Tapered MMI splitters with unconstrained splitting ratio on a thick SOI platform

“…Silicon photonics platforms based on a micron-scale thick device layer 1,2 allow for a unique combination of tight bends [3][4][5] and relatively large modes, enabling dense integration with low propagation losses (down to 3 dB/m demonstrated 6 ) and low coupling losses over a very broad wavelength range. One of the main challenges in these platforms is the realization of compact power splitters.…”