Figure 1.

(a) Illustration of microring resonator (MRR) with radius R fabricated with fishbone sub-wavelength grating (SWG) waveguides and (b) expanded view of bus-to-ring coupling region with coupling gap g_c. Illustrations of (c) strip, (d) conventional SWG, and (e) fishbone SWG waveguide geometries with width w, thickness t, grating period Λ, duty cycle δ, and fishbone width w_fb. (f) Graphical representations of MRR performance criteria, including (clockwise from top left) critically coupled quality factor (Q_crit), free spectral range (FSR), intrinsic limit of detection (iLoD), and bulk sensitivity (S_b).