High-power low-divergence tapered quantum cascade lasers with plasmonic collimators

We demonstrate a tapered quantum cascade laser with sloped side-walls emitting a high-brightness single-lobe beam at 8.1 μm with a peak power of 4 W at room temperature. Using a combination of high and low reflectivity facet coatings, the power output is increased to 6.2 W while a high beam quality is maintained. Plasmonic collimators are fabricated on the facet of the uncoated lasers without compromising power output, demonstrating the viability of this beam-shaping strategy for high-power lasers. The collimated lasers emit a beam with a more circular cross-section, which is more amenable to high-efficiency coupling into mid-infrared optical fibers.