Far-infrared and ultra-high-speed quantum-cascade lasers

Quantum cascade (QC) lasers, invented and first demonstrated at Bell Labs in 1994, already outperform all other mid-infrared (IR) semiconductor laser technologies in terms of optical power and spectral agility and are now commercially available. They can be designed to cover the entire mid-IR spectrum and part of the far-IR spectrum (3-24 mum) using the same material. They are also the only compact lasers capable of broad continuous single mode tuning in the mid-IR and in particular in the two atmospheric windows (3-5 mum and 8-13 mum). The latter regions can be used advantageously for the detection of many trace gases and vapors, down to parts-per-billion by volume (ppbv), for applications such as pollution detection, atmospheric chemistry and industrial process monitoring and control. QC lasers have already achieved many important milestones in trace gas detection via a large variety of spectroscopic techniques. QC lasers are the first mid-IR semiconductor lasers to operate pulsed at room temperature and above and have also achieved record powers (over 1 W) in both pulsed and CW mode. The above power levels are three orders of magnitude higher than those of commercial lead salt lasers. Using AlInAs/GaInAs heterostructures lattice matched to InP, our group has covered the entire range from 4.3 to 24 mum. Using strained layered AlInAs/GaInAs, this range has been extended to 3.4 mum