Fig. 2: Device fabrication and measurement set-up.

a SEM image of a full quasi-2D snowflake OMC device fabricated on SOI. This device is an “8-shield device” in which an additional eight periods of cross-structure phononic bandgap shielding is applied at the periphery (see Supplementary Note 4). A lensed optical fiber is used to couple light into a tapered on-chip waveguide, which is butt-coupling to the quasi-2D snowflake OMC cavity. b SEM image of the center of the cavity region. Fitting to the geometries for “C”-shaped holes and snowflake holes in the cavity region are shown as red solid lines. c Measured “C” parameters fit from SEM images of a fabricated cavity (dots) along with their design values (dashed curves). Shown over one half of the cavity (first 8 “C” shapes on the right side of the cavity) are the parameters (from top to bottom): h_o (cyan circles), w_o/2 (green squares), h_i (blue crosses), and w_i/2 (red triangles). Error bars in geometrical parameters correspond to standard deviation of ten sets of measured SEM images. d Experimental set-up for characterization of the quasi-2D snowflake OMC cavity. Multiple optical switches are used to switch between continuous wave and pulsed optical excitation and between heterodyne spectroscopy and single photon detection. AOM acousto-optic modulator, EOM electro-optic modulator, EDFA erbium-doped fiber amplifier, VC variable coupler, BDP balanced photodetector, SPD single photon detector. A more detailed schematic and description of the measurement set-up is provided in Supplementary Note 2.