Reduction of Facet Reflectivity of Quantum-Cascade Lasers With Subwavelength Gratings

We demonstrate the reduction of the facet reflectivity of quantum-cascade lasers (QCLs) by using subwavelength gratings. The gratings were fabricated on lambda=4.9- and 9.8-mum QCLs using focused ion beam milling. Reflectivities as low as 1%-3% for the 4.9-mum QCL and as low as 4%-8% for the 9.8-mum QCL are reported