High Extinction Ratio Subwavelength Grating Ring Resonator

Compared with the conventional strip waveguide, subwavelength grating (SWG) waveguide has an enhanced evanescent field penetrating deeper within the upper cladding and the propagation direction, and an increased light-matter interaction can be achieved, resulting in a larger optical loss simultaneously. We experimentally demonstrate a subwavelength grating ring resonator around 1310nm. In order to reduce the influence of optical loss in the subwavelength bus waveguide and ring waveguide, we optimized the ring resonator by scanning the gap between the ring resonator and bus waveguide when the silicon duty cycle is fixed. The results experimentally show that the maximum extinction ratio of 18.8 dB when the gap and silicon duty cycle are equal to 120 nm and 0.7 around 1310nm. The extinction ratio has a 4.2dB larger than that for the resonance around 1550nm, which marks an increase of 28.7% compared to the C-band micro-ring sensors, thus showing a potential for bio-sensing applications in Lab-on-Chip system.