Ultrahigh Q SOI ring resonator with a strip waveguide

The design and experimental demonstration of a large, ultrahigh-quality (Q) factor, and single-mode operation silicon ring resonator based on a strip silicon photonic waveguide are presented. The ring resonator comprises multimode straight strip waveguides (MMWG), single-mode strip waveguides (SMWG), 90° Bezier bends, and linear tapers. The SMWG are used in the coupling region to achieve mode coupling for the fundamental mode without exciting the higher-order mode. The MMWG, 1.6 μm in width, are used to decrease the propagation loss. The taper smoothens the straight-to-bend transition and reduces the intermode crosstalk at the interface between the straight and bent waveguides. The design of the 90° Bezier bend ensures that only the maintained fundamental mode propagates at the bend with ultralow loss and low intermode interference. The resonator fabricated in this study had an ultrahigh-Q factor of 1.54 × 106, with a free spectrum range of 0.036 nm, and achieved an actual loss of unit transmission of approximately 0.25 dB/cm.