Mid-infrared wavelength multiplexers on an InP platform

We demonstrate mid-infrared multiplexers based on evanescent couplers in In0.53Ga0.47As/InP ridge waveguides. Multiplexing of λ = 5.2 µm and λ = 8 µm input wavelengths in TM00 modes to a single TM00 output was achieved with 0.7 dB insertion loss. The demonstrated multiplexing bandwidth is significantly broader than is achievable using typical arrayed waveguide gratings, while displaying comparable insertion loss. These devices will be essential toward the development of broadband multi-color mid-infrared photonic integrated circuits for multi-species gas sensing and multi-band mid-infrared free-space communications.