Coupled-waveguides for dispersion compensation in semiconductor lasers

The generation of optical frequency combs via direct electrical pumping of semiconductor lasers is an attractive alternative to the well-established mode-locked laser sources in terms of compactness, robustness and integrability. However, the high chromatic dispersion of bulk semiconductor materials can prevent the generation of frequency combs or lead to undesired pulse lengthening. In this letter, we present a novel dual waveguide for intracavity dispersion compensation in semiconductor lasers. We apply the concept to a short mid-infrared wavelength quantum cascade laser operating in the first atmospheric window (\lambda $ \approx$ 4.6 \mu m). As a result, stable comb operation on the full dynamical range is achieved in this device. Unlike previously proposed schemes, the dual waveguide approach can be applied to various types of semiconductor lasers and material systems. In particular, it could enable efficient group velocity dispersion compensation at near-infrared wavelengths where semiconductor materials exhibit a large value of that parameter.