5 - Dye Lasers

Abstract

This chapter elaborates on the performance and basic features of dye lasers. Laser dye molecules are large, with atomic weights in the 175- to 1000-amu range. A feature of dye laser molecules is that each electronic state contains a multitude of overlapping vibrational-rotational levels. The broadband nature of the emission is a consequence of the involvement of the vibrational manifold of the ground electronic state. It is found that as the gain medium exhibits homogeneous broadening, the introduction of intracavity dispersive elements enables all the excited molecules to contribute efficiently to the narrow-linewidth emission. Ultraviolet lasers—such as excimer lasers or nitrogen lasers—can be used to excite a large number of dyes whose emissions span the spectrum from the near ultraviolet to the near infrared. In the case of oscillator excitation, the beam waist of the laser emission should be determined by the diffraction conditions necessary to restrict emission to a single-transverse mode. A very important parameter in narrow-linewidth dye laser oscillators is the amplified spontaneous emission (ASE) level. One approach to quantify the ASE level is to measure the ASE percent present in the output. The flashlamp-pumped dye lasers are also discussed in the chapter.