1. Introduction
Tunable diode laser spectroscopy (TDLS) has recently attracted much attention as an extremely effective tool for reducing global warming and air pollution and contributing to a safe and secure society, because this technique will afford selective detection and precise quantification of various gases. Various technological advances including laser sources and sensing technologies for increasing sensitivity and precision has expanded the TDLS application field. We describe recent progress on laser light source technology for TDLS and some TDLS application examples.