Single crystals with internal doping with laser ions prepared by a hydrothermal method

Single heterogeneous crystals are described that contain multiple regimes, adjacent regimes varying from one another with regard to function. Also disclosed is a hydrothermal epitaxial growth process that can be utilized to form the single heterogeneous crystals. The single heterogeneous crystals can exhibit enhanced performance when used as a laser gain medium as compared to previously known single crystals and multi-crystal constructs. The heterogeneous single crystal can be utilized for thin disk lasers and can minimize the thermal distortion effects at high powers. The heterogeneous crystal can also serve as an embedded waveguide