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

We present quantum cascade laser designs at 7 - 9 μ m 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.