Gas sensing using slow light in photonic crystal waveguides

We introduce a novel gas sensor based on photonic crystal (PhC) waveguides where the gas sensing is based on the interaction between the slow light mode and the gas. Specifically, when the refractive index of the photonic crystal waveguide changes (due to a change in gas), the slow light regime of the photonic crystal waveguide is affected and shifts in wavelength. We have performed experiments with Helium and Argon gases to confirm the operation of the sensor, with Air being used as reference gas. Results show that the slow light regime typically shifts by 0.6 nm for Helium and 0.05nm for Argon.