ABSTRACT
Host materials for lasers are classified into three groups: crystals, glasses, and ceramics. Host materials should be uniform and large enough for laser action volume, and have excellent optical mechanical and thermal properties. Mechanical and thermal stabilities are important for stable laser oscillation under strong pumping and thermal stress. Thermal conductivity is also important for dissipating heat generated by pumping, and the thermal expansion coefficient is also important for keeping good beam properties. Laser oscillation is analyzed on a model using the concepts of population inversion and energy levels in lasing materials. Solid-state lasers have become popular because a wide range of coherent light is obtained by utilizing nonlinear crystals for wavelength conversion and semiconductor lasers for pumping. Diode-pumped solid-state lasers are widely used in semiconductor, display, and solar panel manufacturing industries. Yttrium aluminum garnet, discovered in 1969, is one of the best host materials and possesses good optical, thermal, and mechanical properties.
