ABSTRACT
Lasers are uniquely suited to applications in precision measurement due to their output beam spatial and spectral characteristics. They emit light in a near diffraction-limited beam and may also emit in a single longitudinal mode, with a narrow linewidth. By way of introduction to this chapter, a few comments covering spatial characteristics are given, in so far as they can affect the stabilization and application of narrow linewidth lasers. Subsequently, we concentrate solely on spectral characteristics.
