Monolithic coupling of QCLs in evanescent waveguides on InP

In this work we present a significant step toward monolithic multiplexed distributed feedback (DFB) quantum cascade lasers (QCL) array on indium phosphide (InP). A multi-wavelength DFB-QCL array evanescently coupled to an underlying InGaAs waveguide on iron doped InP wafer is presented. We introduce the design, optimization, simulation and fabrication of the adiabatic coupler ensuring high transfer efficiency from the active to the passive waveguide. The active region designed in 7 mu m - 10 mu m wavelength range is grown by molecular beam epitaxy on top of an InGaAs waveguide. Components are defined during postgrowth processing, which eliminates the need for material regrowth or bonding techniques. With the present design, one could realize a broadly tunable, mechanically robust, single-mode output source which can be used in spectroscopic applications.