On-chip mid-infrared optical sensing with GeSbSe waveguides and resonators.

We fabricated single mode GeSbSe waveguides and resonators using e-beam lithography and achieved a propagation loss of 3.88 dB/cm at 3.66 µm. We compared BCl and CHF etch chemistries and determined CHF produced 1.5 dB/cm higher propagation losses at 3.6 µm due to C-H bond absorption. We use fabricated waveguides to detect an aromatic aldehyde dissolved in a non-polar solvent with a limit of detection of 1.09 µmol/mL. We then reduce this detection limit to 0.25 µmol/mL using the enhancement produced by a chalcogenide ring resonator.