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Silicon carbide (SiC) has great potential for optomechanical applications due to its outstanding optical and mechanical properties. However, challenges associated with SiC nanofabrication have constrained its adoption in optomechanical devices, as embodied by the considerable optical loss or lack of integrated optical access in existing mechanical resonators. In this work, we overcome such challenges and demonstrate a low-loss, ultracompact optomechanical resonator in an integrated 4H-SiC-on-insulator (4H-SiCOI) photonic platform for the first time, to our knowledge. Based on a suspended 4.3-μm-radius microdisk, the SiC optomechanical resonator features low optical loss (<1  dB/cm), a high mechanical frequencyf_mof 0.95×10⁹  Hz, a mechanical quality factorQ_mof 1.92×10⁴, and a footprint of <1×10⁻⁵  mm². The correspondingf_m·Q_mproduct is estimated to be 1.82×10¹³  Hz, which is among the highest reported values of optomechanical cavities tested in ambient environment at room temperature. In addition, the strong optomechanical coupling in the SiC microdisk enables coherent regenerative optomechanical oscillations at a threshold optical dropped power of 14 μW, which also supports efficient harmonic generation at increased power levels. With such competitive performance, we envision a range of chip-scale optomechanical applications to be enabled by the low-loss 4H-SiCOI platform. 

Abstract Beta gallium oxide (β‐Ga₂O₃) has emerged as a highly promising semiconductor material with an ultrawide bandgap ranging from 4.5 to 4.9 eV for future applications in power electronics, optoelectronics, as well as gas and ultraviolet (UV) radiation sensors. Here, surface adsorption and air damping behavior of doubly clamped β‐Ga₂O₃nanomechanical resonators are probed and systemically studied by measuring the resonance characteristics under different gas and pressure conditions. High responsivities of resonance to pressure are obtained by heating the devices up to 300 °C to induce an accelerated adsorption–desorption process. The initial surface conditions of the β‐Ga₂O₃thin film play important roles in affecting the resonant behavior. UV ozone treatment proves effective in altering the initial surface conditions of β‐Ga₂O₃nanosheets by eliminating physisorbed contaminants and filling oxygen vacancy defects residing on the surface, resulting in a consequential and discernible modification of the resonance behavior of β‐Ga₂O₃nanomechanical resonators. The surface adsorption and desorption processes in β‐Ga₂O₃demonstrate clear reversibility by exposing the UV treated β‐Ga₂O₃to air. This study attains first‐hand information on how the surface conditions of β‐Ga₂O₃affect its mechanical properties, and helps guide future development of transducers via β‐Ga₂O₃nanoelectromechanical systems (NEMS) for pressure sensing applications, especially in harsh environments.