High-Q mid-infrared chalcogenide glass resonators

In this letter, we fabricated and characterized chalcogenide glass resonators monolithically integrated on mid-infrared transparent CaF2 substrates. The devices feature an intrinsic Q-factor of 4E5 at 5.2 micron wavelength, which represents the highest Q-factor reported in planar mid-infrared resonators. It is found that moisture can significantly impact the device performance when the device was exposed to an ambient environment, although the high-Q characteristics can be restored after undergoing an annealing treatment. Using these devices, we further demonstrated on-chip cavity-enhanced spectroscopy to quantify mid-IR absorption of ethanol solutions around 5.2 micron wavelength.