Single-mode interband cascade laser with a slotted waveguide

The design of a single-mode interband cascade laser (ICL) using a slotted waveguide is presented. This technique was explored as an inexpensive alternative to distributed feedback lasers since standard photolithography can be used in fabrication and complex techniques, such as e-beam lithography, re-growth steps, and/or metal gratings, can be avoided. The design of slotted waveguides must be carefully simulated before fabrication to ensure the efficacy of the photolithography masks with each ICL growth. Limitations and the behavior of key design parameters are discussed. Single-mode emission was achieved for certain temperature and injected current conditions, validating the operation of an Sb based slotted laser. The slotted ICLs were emitting from a single longitudinal mode at 3.5  μm and 2 mW of power per facet output at 20 °C with threshold currents around 80 mA.