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

We fabricated single mode Ge28Sb12Se60 waveguides and resonators using e-beam lithography and achieved a propagation loss of 3.88 dB/cm at 3.66 mu m. We compared BCl3 and CHF3 etch chemistries and determined CHF3 produced 1.5 dB/cm higher propagation losses at 3.6 mu m 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 mu mol/mL. We then reduce this detection limit to 0.25 mu mol/mL using the enhancement produced by a chalcogenide ring resonator.