A mounting arrangement for mounting a slab of laser host material in a face pumped laser is provided which is operable to isolate the host from flexing caused by differential thermal expansion of the laser housing relative to the host mounting members. First and second stainless steel pedestals are respectively secured to the aluminum housing and first and second elongated, stainless steel rail support members are pivotally secured, respectively, through a pair of flex pivots each, to the first and second pedestals for isolating the support members from flexure of the pedestals. The host is secured between and to the rail support members by bonding with an RTV compound. In the preferred embodiment, one of the rail support members is provided with a diaphragm on one of its sides along the entire length thereof, to which is bonded one of the sides of the host, thus providing further isolation of the host from stresses caused by thermal expansion.

Two solid state laser structures are provided which are optimized for multimode operation. The first laser structure has a plurality of normal incidence optically transmissive surfaces in the laser cavity. The most reflective one of those normal incidence surfaces is disposed at the optical center of the laser cavity. The gain medium is centered in the subcavity defined by a cavity mirror and the optical center. In the second laser structure, there are no normal incidence surface in the laser cavity, and the gain medium is disposed at the optical center of the laser cavity. The laser structures are employed to construct erbium glass lasers which are not only optimized for multimode operation but also have effective cooling of the gain medium and minimized thermal lensing effect.

A monolithic solid state laser structure is used to construct erbium lasers that are insensitive to external pressure changes and vibrations, and have improved cooling of the gain medium and reduced thermal lensing effect. In the monolithic laser structure, the gain medium is separated from an optically transmissive plate on one side and a wave plate on the other side by spacers to form narrow air gaps which provide effective cooling of the gain medium and reduced the thermal lensing effect. Such an arrangement is further combined with a pressure-insensitive Brewster polarizer, such as a solid Brewster polarizer or a pressure-sealed Brewster plate, to form a pressure-insensitive laser cavity. The wave plate cooperates with the Brewster polarizer to select the wavelength of the solid state laser.

A side-pumped solid laser employs diode array pumping to produce a near-diffraction-limited output beam in at least one dimension of the output beam, while maintaining high efficiency operation. Conversion efficiency is enhanced by orientation of a nonlinear crystal for enhanced beam quality along one axis, while improved beam quality is obtained in the other dimension by increasing absorption of the diode light within the laser crystal, reducing the crystal width, and/or a multi-pass reflector on the crystal face opposite the pumped face. The laser may be used in frequency doubling or wavelength shifting systems employing non-linear optical media. In that case, the output beam has its good axis preferentially aligned to enhance stability or prevent walkoff.