ABSTRACT
Many lasers exhibit partial spatial or temporal coherence properties, which can have a substantial effect on the propagation of the light beams they generate. Some examples of laser sources with reduced spatial coherence properties are multi-spatial-mode solid-state, gas or semiconductor lasers, excimer lasers, free-electron lasers (FELs), as well as many random lasers and vertical-cavity surface-emitting laser (VCSEL) arrays. On the other hand, excimer lasers and multi-longitudinal-mode continuous-wave lasers
also have rather limited temporal coherence properties, which restrict their use in, for example, interference experiments. Finally, there are pulsed sources that are spatially nearly coherent but can have quite arbitrary temporal coherence; the prime examples of these are sources of supercontinuum (SC) light. In this chapter, we apply the secondorder coherence theory of both stationary [1,2] and nonstationary [3-5] light to model continuous-wave and pulsed low-coherence laser sources. We further look at some aspects related to focusing, imaging, and controlling the spatial shape of beams generated by such lasers.
