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 degrees 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 mu m 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 degrees 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 x 10(6), with a free spectrum range of 0.036 nm, and achieved an actual loss of unit transmission of approximately 0.25 dB/cm.