Page 18 - Tunable Lasers Handbook

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1. INTRODUCTION

Tunable sources of coherent radiation are suitable for a wide range of appli-
cations in science, technology, and industry. For instance, the first broadly tun-
able laser source, the dye laser, is used for a plethora of applications in many
diverse fields [ 11 including physics [24], spectroscopy [5,6], isotope separation
[6-81, photochemistry [9], material diagnostics [9], remote sensing [9-11], and
medicine [12]. In addition to issues of physics, it is this utilitarian aspect of tun-
able lasers that motivates much of the interest in the field.
In recent years, new sources of tunable coherent radiation have become
available that have either extended spectral coverage or yielded appealing emis-
sion characteristics. Notable among these sources are optical parametric oscilla-
tors and tunable semiconductor lasers.
This field has several natural subdivisions. For instance, although most
sources of tunable coherent radiation are lasers, some sources such as the optical
parametric oscillator (OPO) do not involve population inversion. An additional
classification can be established between broadly tunable sources of coherent
radiation, including broadly tunable lasers, and discretely tunable lasers, and/or
line-tunable lasers. A subsequent form of classification can be the physical state
of the difFerent gain media such as gaseous, liquid, and solid state. Further

Tunable Lasers Handbook
Copyright 0 1995 by Academic Press, Inc. All rights of reproduction In any form reserved