Spiral Waveguides on Germanium-on-Silicon Nitride Platform for Mid-IR Sensing Applications

Spiral waveguides on a new germanium-on-silicon nitride (GON) platform with a wide transparency and a large core-clad index contrast for mid-infrared (mid-IR) sensing applications are demonstrated. Spiral waveguide sensors with a low bending loss on this platform enable compact sensors for mid-IR absorption spectroscopy. A minimum volumetric concentration of 5% isopropanol (IPA) in an IPA-acetone mixture is measured. This detection limit is three times lower than the counterpart waveguide, fabricated on the regular germanium-on-silicon platform with similar propagation loss at 3.73 μm wavelength. This silicon-compatible GON sensor is promising for applications such as environmental studies, industrial leak detection, process control, medical breath analysis, and many more.