Bandgap-engineered semiconductor lasers based on either intersubband or interband cascade structures are emerging in a rapidly expanding wavelength range throughout the midwave-, longwave-, and far-IR. This paper reviews recent progress in applying these new lasers to high-sensitivity sensors of gases, liquid, and solids. General operational characteristics and applications of the most common mid-IR Quantum Cascade Lasers (QCL) will be described. Particular emphasis will be placed on: new interband cascade devices operating near 3.3 microns and used for hydrocarbon detection; cavity-enhanced detection of trace breath species; and far-IR (or THz) wavelength devices used for detection of solid-phase organic crystals such as explosives.
© 2004 Optical Society of AmericaPDF Article