High-quality microresonators in the long-wave infrared based on native germanium

The longwave infrared (LWIR) region of the spectrumspans 8 to 14 mu m and enables high-performance sensing and imaging for detection, ranging, and monitoring. Chip-scale LWIR photonics has enormous potential for real-time environmental monitoring, explosive detection, and biomedicine. However, realizing technologies such as precision sensors and broadband frequency combs requires ultra low-loss and low-dispersion components, which have so far remained elusive in this regime. Here, we use native germanium to demonstrate the first high-quality microresonators in the LWIR. These microresonators are coupled to partially-suspended Ge waveguides on a separate glass chip, allowing for the first unambiguous measurements of isolated linewidths. At 8 mu m, we measured losses of 0.5 dB/cm and intrinsic quality (Q) factors of 2.5 x 10(5), nearly two orders of magnitude higher than prior LWIR resonators. Our work portends the development of novel sensing and nonlinear photonics in the LWIR regime.

Automated summary

High-quality microresonators in the LWIR have been demonstrated using native germanium, paving the way for the development of novel sensing and nonlinear photonics in this regime.