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

Abstract

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 (T0=170 K) in pulsed mode operation at 295 K.