Tapered quantum cascade lasers

The authors report on the fabrication of quantum cascade lasers with tapered gain sections. In order to obtain optimal results, index guided devices were realized with tapered angles varying between 0.9 degrees and 2.6 degrees. Compared to a common ridge waveguide laser (divergence of 48.7 degrees), a very small horizontal beam divergence of 6.6 degrees in the single lobe far field is achieved. The tapered quantum cascade lasers show good performance with peak output powers of more than 200 mW at room temperature at an emission wavelength of similar to 8.9 mu m. (C) 2007 American Institute of Physics.