Diode-pumped broadband vertical external cavity surface emitting semiconductor lasers. Application to high sensitivity intracavity absorption spectroscopy

Abstract

Summary form only given. Absorption spectroscopy is widely used in the laboratory and for in situ measurements. One of the most important issues of any monitoring technique, as important as the sensitivity, is the ability to provide absolute absorption coefficients without the need for complicated and cumbersome calibration procedures. Intracavity-laser-absorption-spectroscopy (ICLAS) is one of the most sensitive techniques capable of providing this absolute information. In the ICLAS technique an absorbing medium with absorption lines narrower than the broadband spectrum of a laser is placed inside the laser cavity. The absorption lines follow the Lambert-Beer law, with an equivalent path length of L/sub eq/=ctg, where the generation time t/sub g/ is the time from the beginning of the laser generation to the moment of observation, and c is the velocity of light. Any type of laser with a homogeneously broadened gain medium can be used. ICLAS allows extreme sensitivity, but, up to now, it has been limited mainly to the 0.6. 1 /spl mu/m range, with expensive and bulky systems.