Strengthened solid-state laser materials

The tensile fracture strength of crystalline materials for high average power lasers has been increased by a factor of 15 using deep chemical polishing. Samples of gadolinium scandium gallium garnet, gadolinium gallium garnet, and yttrium aluminum garnet, which were prepared by conventional mechanical techniques to a high quality polish, were found to contain subsurface damage up to 50 μm in depth. When this damage was removed by deep chemical etching, the mean strength of small, four-point flexure specimens increased from 155 to 2280 MPa; however, these samples were no longer optically flat after etching. Specimens in which the optical figure was restored by polishing after the etch had an intermediate strength of 630 MPa.