Effect of Scaling on the Optical Q of SiN Optomechanical Oscillators*

Cavity optomechanical oscillators (OMOs) have several applications in timing, communications and sensors. For all applications, it is interesting to investigate the effect of reduced device size on optical quality factor, Q. In this study, we measure the optical Q at 1550 nm of released SiN whispering gallery mode resonator OMOs coupled to SiN waveguides. We chose a free space optical setup for flexible mode matching and long-term stability. The setup takes advantage of a top down camera and co-linear, co-focused 635 nm and 1550 nm lasers for easier waveguide coupling. We also describe improvements in automation for real time resonance identification and analysis. The devices measured are discs and anchored ring resonators with varying waveguide coupling gaps and device radii ranging from 10 μm to 60 μm which are suspended with various spoke widths. We achieved Q=2x10⁶ in 50 μm radius discs. A comparison of optical Q as a function of the parameters stated above will be made to determine designs for optomechanical characterization.