Difference frequency generation in AlGaAs Bragg-reflection waveguides using an integrated quantum dot laser

Nonlinear frequency conversion is ubiquitous in laser engineering and entangled photon pair generation, and has applications across quantum technology, for example in erasing spectral distinguishability of single photon emitters. Typically, frequency conversion requires multiple costly and bulky lasers to be coupled into a nonlinear crystal using free space optics that is often challenging due to the large spectral separation of the lasers. Here, we demonstrate nonlinear difference frequency generation (DFG) in an AlGaAs waveguide that is itself the gain medium for one of the required lasers. By including a quantum dot layer in the waveguide, doping the semiconductor and injecting current, we produce laser light at ∼790nm wavelength using the facets of the waveguide to form a cavity. Using this on-chip laser and the Χ⁽²⁾ nonlinearity of AlGaAs, we perform DFG of an external telecom laser. We use the broad phase-matching to perform DFG from 1520-1630nm wavelength. We measure conversion efficiency up to (7.5 ± 2.4) x 10^-2 %/W/cm² which could be readily increased with further engineering to reduce losses and improve thermal management. Our proof-of-concept device has applications in intra-band telecom frequency conversion and for converting quantum emitters to a common wavelength.