A laser gain element including an undoped layer of a monoclinic double tungstate (MDT) crystal, and a method of forming a laser gain element are provided. The laser gain element includes a layer of doped MDT crystal adjacent to the undoped layer, the doped MDT layer including a pre-selected concentration of rare earth ions. The layer of doped MDT crystal has an absorption peak at a first wavelength and an emission peak at a second wavelength longer than the first wavelength; and the layer of doped MDT crystal has a fluorescence emission with a weighted average at a third wavelength shorter than the first wavelength. A laser resonator cavity formed with a plurality of composite gain elements as above is also provided.