Multi-spectral midwave-infrared (mid-IR) lasers are demonstrated by directly bonding quantum cascade epitaxial gain layers to silicon-on-insulator (SOI) waveguides with arrayed waveguide grating (AWG) multiplexers. Arrays of distributed feedback (DFB) and distributed Bragg-reflection (DBR) quantum cascade lasers (QCLs) emitting at 4.7 μmwavelength are coupled to AWGs on the same chip. Low-loss spectral beam combining allows for brightness scaling by coupling the light generated by multiple input QCLs into the fundamental mode of a single output waveguide. Promising results are demonstrated and further improvements are in progress. This device can lead to compact and sensitive chemical detection systems using absorption spectroscopy across a broad spectral range in the mid-IR as well as a high-brightness multi-spectral source for power scaling.
![(a) Top-view schematic of the QCL array and arrayed waveguide grating (AWG). Mirrors are defined under the red III-V QCL ridges for both the distributed feedback (DFB) and distributed Bragg-reflection (DBR) type lasers. (b) Micrograph of a multi-spectral DFB laser, showing the individual lasers on the left and the AWG combiner on the right.](/sites/default/files/styles/medium/public/2019-01/stanton19p_0.png?itok=t0uFOYOQ)