ABSTRACT
The coverage and discussion of laser sources of relevance to modern spectroscopy and imaging is split into two chapters. In this first chapter, coverage of the “traditional/historic” laser sources is provided, addressing lasers based on gaseous, liquid, and solid active media. While in the early years of laser spectroscopy fixed-frequency gas lasers (like the argon ion—Ar+—laser) and tunable-frequency liquid-media lasers (dye lasers) dominated the field, it is fair to say that today these have been largely superseded by lasers based on solid-state active media, safe for a few niche applications. Therefore, the latter receive the main attention in this chapter. In particular, two types of laser sources are discussed, namely lasers utilizing solid-state, doped crystals (by and large, Nd:YAG and its brethren, and Ti:sapphire), and devices based on optical fiber materials. In both cases, the realization of fixed- and tunable-frequency sources is described, as well as system behavior in the most common modes of operation—in the continuous-wave, nanosecond-pulse, and ultrashort pulse (femtosecond) regimes. The chapter concludes with a brief summary on supercontinuum radiation, how it can be generated, and a short evaluation of its usefulness in laser spectroscopy and imaging.
