Chapter 6 Transverse mode shaping and selection in laser resonators

Abstract

This chapter discusses the transverse mode shaping and selection in laser resonators. Laser resonators are categorized as either stable or unstable. In a stable resonator, a ray launched inside the resonator parallel to the optical axis remains inside it, whereas in an unstable resonator, the ray may bounce off the resonator after a few round-trips. The chapter describes transverse modes in stable and unstable resonators, and also the numerical and analytical methods to determine the field distributions of the transverse modes. Various methods to select specific transverse modes in laser resonators, along with techniques for fabricating the needed intra-cavity elements are also described. Intra-cavity elements can be incorporated into laser resonators to shape specific transverse mode patterns and to discriminate and select a specific single mode out of the many modes that exist in the resonator. The properties of the laser output beams include beam quality, output power and field distributions. The analytical tools for describing the properties of the laser output beams, along with selected applications are discussed in the chapter.