Chapter 7 - Pulsed Narrow-Linewidth Tunable Laser Oscillators

Abstract

This chapter describes various aspects of pulsed narrow-linewidth tunable laser oscillators. The basics on interference, the uncertainty principle, polarization, and beam propagation are applied to the design, architecture, and engineering of narrow-linewidth tunable lasers. The gain media assumed here are tunable media either in the gas, liquid, or solid state. The narrower the intracavity aperture and the longer the cavity, the lower the number of transverse modes. The single-pass transverse-mode structure in one dimension can be characterized using the generalized interferometric equation. The single-pass approximation to estimate the transverse-mode structure assumes that in a laser with a given cavity length, most of the emission generated next to the output-coupler mirror is in the form of spontaneous emission, and thus, highly divergent. Tunable laser oscillators without intracavity beam expansion are those laser resonators in which the intrinsic narrow beam waist at the gain region is not expanded using intracavity optics. The chapter also discusses the widely tunable narrow-linewidth external-cavity semiconductor lasers.