Broadband integrated racetrack ring resonators for long-wave infrared photonics.

Long-wave infrared photonics is an exciting research field meant to revolutionize our daily life by means of key advances in several domains including communications, imaging systems, medical care, environmental monitoring, or multispectral chemical sensing, among others. For this purpose, integrated photonics is particularly promising owing to its compactness, mass fabrication, and energy-efficient characteristics. We present in this Letter, for the first time to the best of our knowledge, broadband integrated racetrack ring resonators operating within the crucial molecular fingerprint region. Devices show an operation bandwidth of Δλ≈900  nm with a central wavelength of λ≈8  μm, a quality factor of Q≈3200, and an extinction ratio of ER≈10  dB around the critical coupling condition. These resonant structures establish the basis of a new generation of integrated building blocks for long-wave infrared photonics that opens the route towards miniaturized multitarget molecule detection systems.