QUANTUM CASCADE LASERS

Abstract

IF THE CONDENSED history of infrared spectroscopy were written in biblical prose, the text might read: “In the beginning, dispersive instruments ruled. Then came the Fourier transform spectrometers, and the older instruments disappeared in a great purge.” The next verse in that ultrashort summary might not be recorded yet, but when molecular spectroscopy scribes put pen to parchment, they will certainly stress the field’s rapid advances due to the advent of quantum cascade (QC) lasers. To give a sense of the progress made with these semiconductor-based light sources and their importance to chemical analysis, the field’s devotees stress the remarkable timescale over which they were developed and commercialized as well as the breadth of their applications. “It has only been about 15 years since QC lasers were first demonstrated,” says chemistry Nobel Laureate Robert F. Curl Jr. of Rice University. “Yet in that short amount of time, these devices have become the most useful sources ...