Suspended InGaAs membrane waveguide devices with subwavelength gratings and photonic crystal structures for ammonia sensing at lambda=6.15um (Conference Presentation)

Fully suspended InGaAs waveguide devices with holey photonic crystal waveguides (HPCWs) and Sub-wavelength waveguides (SWWs) are designed and fabricated for mid-infrared sensing at λ=6.15µm in the low index contrast InGaAs-InP platform. We experimentally detect 5 ppm ammonia in 1 mm long suspended HPCW and 3 mm long suspended SWW with propagation loss of 39.1 dB/cm and 4.1 dB/cm, respectively. This result emphasizes the advantage of SWWs which can utilize the longer devices by virtue of its low propagation loss to increase the gas sensing sensitivity compare to HPCWs.