Ultra-low threshold lasing through phase front engineering via a metallic circular aperture

High performance distributed feedback quantum cascade laser emitting at λ∼6.12um

Distributed feedback quantum cascade lasers emitting at a wavelength of 6.12 µm are reported. Benefitted from the optimized materials epitaxy and the modified bound to continuum transition active region design along with three pairs of phonon scattering, high device performance is achieved. For a 2-mm-long, 8.4-µm-wide device, the threshold current is as low as 130 mA, the corresponding threshold current density is only 0.77 kA/cm², and the optical output power is 69 mW at 20 °C in continuous wave mode. The temperature of continuous wave operation can reach 100 °C, where the optical output power is still more than 8 mW. In addition, it maintains a stable single mode operation from 20 to 100 °C without mode hopping, corresponding to a total wavelength shift of 41 nm. Such low-threshold quantum cascade lasers are highly beneficial to portable and highly integrated system sensor applications.