Hydrothermal growth of hexagonal beryllium borate crystals for use in laser non-linear optical and birefringent applications and devices

Single, acentric, hexagonal, beryllium borate crystals having the formula Sr.sub.2Be.sub.2B.sub.2O.sub.7 and of a size sufficient for use in a variety of laser and non-optical applications are formed by a hydrothermal method. Alternate structures are formed by partially substituting the strontium ion with at least one other divalent metal ion