Bob Shine and Tim Day, New Focus Inc.
Environmental issues such as global warming, ozone depletion and
photochemical air pollution have increased concern about how pollutants
affect the environment. This has led to an increased emphasis on detecting
pollutants, understanding their sources of origin and measuring their
concentrations in the environment. Laser-based detection methods are useful
for these measurements; absorption spectroscopy can provide high detection
sensitivity of many different species.
The system designer has many alternatives when choosing semiconductor
lasers and system configurations for spectroscopy applications. The
price/performance trade-offs create myriad possibilities, each of which has
advantages for specific applications. This article addresses the trade-offs
among Fabry-Perot semiconductor lasers, external-cavity diode lasers and
distributed feedback lasers and suggests ideal uses in research &
development and commercial applications.