ABSTRACT
Arguably, semiconductor laser sources have not only revolutionized laser technology in general (with respect to versatility, miniaturization, and cost) but also helped many laser spectroscopic and imaging techniques to rapid penetration into commercial exploitation and into the development of novel applications. In this chapter, the fundamental principles and operation intricacies of lasers based on semiconductor materials as the active medium are described, both for interband (conventional junction lasers) and intraband (quantum cascade lasers) devices. The general description is complemented by relevant equations describing the key features of these laser sources. In addition, practical solutions for versatile laser setups—like external cavity configurations—are discussed, which provide bandwidth control and wide tunability. In the second part of the chapter, laser radiation phenomena and sources are discussed, which exploit nonlinear phenomena in (mono-) crystalline materials. These include “passive” laser light generation—in the form of harmonics, sum, and difference frequency generation—and “active” laser sources, based on cavity-supported optical parametric processes. The chapter concludes with a reminder on laser safety issues and measures: all too often, novice and experienced users alike tend to forget that even the smallest-size modern lasers may be able to cause damage to our precious eyesight.
