Broadband quantum cascade laser gain medium based on a "continuum-to- bound" active region design

We present quantum cascade laser designs at 7-9 μm with two lower injector states strongly coupled with the upper laser state at the operating electric fields. Optical transitions from these three coupled states contribute to a large gain spectrum width (∼250 cm-1 full width at half maximum), which enables external cavity tuning of the lasers over 200 cm-1. Lasers show comparable performance to the conventional narrow band design at a similar wavelength with a peak modal gain coefficient of ∼10 kA/cm, a slope efficiency ∼1 W/A, and good temperature performance (T 0=170 K) in pulsed mode operation at 295 K.