Long-wave infrared integrated resonators in the 7.5–9 μm wavelength range

We present broadband on-chip resonators based on SiGe graded-index waveguides operating in the long-wave infrared spectral range from 7.5 to 9.0 μm wavelength range. A quality factor up to 105 has been measured, while an intrinsic quality factor of 1.13 × 105 has been extracted from the measurements. Thermal tuning of the phase in the micro-ring has been used to overcome the limitation of the experimental setup in terms of spectral resolution. These results pave the way toward the development of integrated frequency comb operating in the long-wave infrared range.