ABSTRACT
The design of optimised resonators for use with solid–state lasers has been a topic of extensive research since the operation of the first ruby laser in 1960. To facilitate the use of specific practical examples, this chapter concentrates on the use of the laser material Nd:YAG in rod geometry; however, similar arguments can be applied to other materials such as Nd:glass and Ruby. For repetitively pulsed systems a quasi-steady state regime is reached in which the temperature profile is given by the sum of the particular profile produced after a single pulse and that remaining after thermal relaxation from the previous pulses. The level of output power from a Nd:YAG laser is approximately half of the level of absorbed power; thus, in order to achieve only low losses (for example less than 10% per pass), only low output powers are permitted.
