Characterization of Mid-Infrared Silicon-on-Sapphire Microring Resonators With Thermal Tuning

Microring resonators on silicon-on-sapphire (SOS) were characterized at 2.75 $\mu\hbox {m}$ wavelength. We obtained a $Q$ factor of 11400 $\pm$ 800. The thermo-optic coefficient of epitaxial silicon of SOS wafer was measured to be $2.11 \pm 0.08 \times 10^{-4} \hbox {K}^{-1}$ . We also describe a characterization technique to measure the $Q$ of microring resonators using a fixed wavelength source. By only varying the temperature of the device, it is possible to measure the $Q$ of a mid-infrared (mid-IR) microresonator. The proposed method provides an alternative method of $Q$ measurement for microring resonators in mid-IR, where tunable lasers may not be easily available. The technique was used to determine the $Q$ of SOS microring resonators at 2.75 $\mu\hbox {m}$ wavelength.