Teledyne FLIR Laser Crystals and Components offers high quality Yttrium Orthoaluminate, also referred to as yttrium aluminum perovskite (YAP), doped with Tm, Nd, Pr, Er and Cr.
YAP´s hardness and thermal conductivity are similar to YAG, but exhibits a highly anisotropic thermal expansion coefficient and is birefringent. YAP is an orthorhombic negative biaxial crystal belonging to the D162h (Pnma) space group. Emission wavelengths are polarized, and emission and absorption cross sections are dependent upon the crystallographic orientation. Teledyne FLIR Laser Crystals and Components (along with references  and  below), use the Pnma space group convention for defining the crystallographic a, b, and c-axis lattice constants. Others (including reference ) use the Pbnm convention. In the table below, we related the two conventions thru their common lattice constants.