Abstract

Quantum cascade lasers (QCL.s)^1,2 have greatly increased the availability of tunable lasers emitting in the mid-to long-wave infrared spectral regions. Due to the abundance of spectroscopic signatures from compounds used in a vast array chemical processes, high-resolution spectroscopy^3,4 and chemical sensing⁵ are very important and topical applications for such laser sources. QCL.s are intrinsically low-noise due to their near-zero alpha parameter,^1,6,7,8 have good control characteristics and lend themselves well to laser stabilization.⁹ This makes them ideal for high performance cavity-based chemical detection schemes such as Noise-Immune Cavity-Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS).¹⁰⁻¹⁴

© 2002 Optical Society of America