Quantum cascade laser emits at 11 microns
Offering an alternative to lead-salt lasers, cooled quantum cascade lasers have produced milliwatts of continuous-wave (CW) and pulsed-mode output power at 11.2 µm (see Laser Focus World, Dec. 1996, p. 9). Demonstrated by Carlo Sirtori and collaborators at Lucent Technologies Bell Laboratories, (Murray Hill, NJ), the current devices consist of 25 aluminum indium arsenide/gallium indium arsenide heterostructures lattice-matched to an indium phosphide substrate; superlattice injectors between the active regions serve as energy relaxation regions for electrons exiting the previous stage.
The devices operated pulsed mode u¥to 200 K and reached maximum optical powers, in excess of 50 mW, at 110 K. Threshold current density was 3.2 kA/cm2 at 10 K, doubling at 170 K. In CW mode, output power was 7 mW at 10 K and about 1 mW at the maximum operating temperature of 30 K