High-quality factor, high-confinement microring resonators in 4H-silicon carbide-on-insulator

Abstract

Silicon carbide (SiC) exhibits promising material properties for nonlinear integrated optics. We report on a SiC-on-insulator platform based on crystalline 4H-SiC and demonstrate high-confinement SiC microring resonators with sub-micron waveguide cross-sectional dimensions. The Q factor of SiC microring resonators in such a sub-micron waveguide dimension is improved by a factor of six after surface roughness reduction by applying a wet oxidation process. We achieve a high Q factor (73,000) for such devices and show engineerable dispersion from normal to anomalous dispersion by controlling the waveguide cross-sectional dimension, which paves the way toward nonlinear applications in SiC microring resonators.

Silicon carbide color centers for quantum applications

“…The emitters' lifetimes in the excited state is around 10 ns [70,78]. The coupling of such defects with photonic elements such as solid immersion lenses [69], nanowires [159,160], nanopillars [18] or PhC cavities, microdisks and micro-ring resonators [2,108,138,[161][162][163][164][165][166][167][168] enhances/controls the photon flux collection.…”

“…The polytype choice for photonics cavity fabrication has been mostly in 3C with few exceptions where 4H was used. Heteroepitaxial growth of thin layers of cubic 3C-SiC on a Si wafer is a method for building nanophotonic devices [163,166,168,178,179], and it has been used initially to test the material. However, the quality of the 3C material growth on Si may not allow reaching the required quality factor for implementing quantum photonics as well the defects in 3C SiC are less known than 4H, where most of the above demonstrations have been achieved.…”

“…However, the quality of the 3C material growth on Si may not allow reaching the required quality factor for implementing quantum photonics as well the defects in 3C SiC are less known than 4H, where most of the above demonstrations have been achieved. The smart-cut techniques applied to hexagonal-polytype thin films grown on oxide [161,168] have also been used, however, due to the material damage, so far the quality factor achieved is deemed not optimal for the intended applications, where high optical Q is required. Suspended structures can be derived from hexagonal SiC by selective etching, producing devices such as PhC cavities and whispering gallery mode resonators, with quality factors up to 50 000 [11,164,165,180].…”

“…Both 3C and 4H SiC can be achieved on insulator (SiCOI), based on direct wafer bonding rather than smart cut techniques and thinning of the material, methods now developed at the wafer-scale level. Recent experiments on wafer bonding of 3C on Insulator have provided microdisks with Q=143 000 [138], while in 4H integrated circuits such as micro-ring resonators [168] with a Q=73 000, photonic crystal nanocavities [182] with Q=630 000, and photonics waveguides [183]. Direct wafer bonding holds the promises to improve the final Q and optical quality of the resonators and be able to provide an integrated platform for nonlinear photonics and integrated quantum circuits in SiC.…”

High-Q suspended optical resonators in 3C silicon carbide obtained by thermal annealing

“…Recent work on the SiC on-insulator (SiCOI) platforms such as 3C and 4H SiC have garnered much interest [26][27][28]. In 3C-SiCOI a flip, bond, etch and polish method was developed to bond 3C-SiC onto an insulating wafer of thermal SiO 2 on Si [26].…”