Ultrahigh Q SOI ring resonator with a Hermite or B-spline curved waveguide

Two new, to the best of our knowledge, designs for a huge, single-mode operation, ultrahigh quality factor SOI ring resonators based on the 90° bend of the B-spline curve and the Hermite curve were demonstrated. The ring resonators comprise multimode straight strip waveguides (MMWG), single-mode strip waveguides (SMWG), 90° bends, and tapers. The TE 0 -TE 0 transmission loss of the bends can reach 0.000013 dB and 0.000091 dB, and the TE 0 -TE 1 excitation ratios reach −48dB and −50dB, respectively, when the bends were designed using the Hermite curve or B-spline curve. Two SOI ring resonators of about 3.00 cm length consisting of the structures mentioned above are manufactured. The first was made up of Hermite curves with 90° bends. It could achieve a Q factor of 4.65×10 6 and a free spectrum range (FSR) of 0.025 nm. The second one employed B-spline curves with 90° bends. It could reach a Q factor of 4.37×10 6 and FSR of 0.022 nm.