From CO2 laser to quantum cascade lasers-A saga of high power infrared lasers

The era of high continuous laser power in the infrared region of the spectrum started with the first demonstration of laser action on the vibrational-rotational transitions of molecules and the invention of the carbon dioxide laser [C. K. N. Patel, "Interpretation of CO2 Optical Maser Experiments," Phys. Rev. Lett. 12, 588-590 (1964)] in 1964. The progress in the high power molecular lasers was swift and led to an explosion of scientific and practical applications in the infrared. The romance with high power infrared lasers that started with in 1964 is still very much alive today. New types of infrared lasers, notably the quantum cascade lasers (QCLs) are carving out a special niche in this arena. Applications of these lasers abound, both in science and industry. In reviewing the fun and excitement of the past as well as what may be in store for us in the future, I will focus on the current impact of the high power midwave and long wave infrared QCLs [A. Lyakh, C. Pflugl, L. Diehl, Q. J. Wang, Federico Capasso, X. J. Wang, J. Y. Fan, T. Tanbun-Ek, R. Maulini, A. Tsekoun, R. Go, and C. Kumar N. Patel, "1.6 Watt, High Wallplug Efficiency, Continuous-Wave Room Temperature Quantum Cascade Laser Emitting at 4.6 mu m," Appl. Phys. Lett. 92, 111110 (2008)] in many defense and homeland security related applications [C. K. N. Patel, "Laser Photoacoustic Spectroscopy Helps Fight Terrorism: High Sensitivity Detection of Chemical Warfare Agent and Explosives," Eur. Phys. J. Spec. Top. 153, 1-18 (2008)]. In this paper I will recount some of the key advances in the high power lasers and their applications. (C) 2010 Laser Institute of America.