On-chip gas detection in silicon optical microcavities.

We demonstrate a chip-scale photonic system for the room-temperature detection of gas composition and pressure using a slotted silicon microring resonator. We measure shifts in the resonance wavelength due to the presence and pressure of acetylene gas and resolve differences in the refractive index as small as 10(-4) in the near-IR. The observed sensitivity of this device (enhanced due to the slot-waveguide geometry) agrees with the expected value of 490 nm/refractive index unit.