Grating-coupled surface emitting quantum cascade ring lasers

We report on the fabrication and operation of quantum cascade ring lasers providing grating-coupled surface emission. The devices exhibit tunable far fields, ranging from spot- to ring-shaped symmetric beam cross sections, depending on the grating period. This-along with threshold current densities as low as for comparable Fabry-Perot lasers-dernonstrates the compatibility of reduced beam divergence and two-dimensional integrability, resulting in an attractive light source for applications in midinfrared spectroscopy and imaging. (c) 2008 American Institute of Physics.