Method for enhancement of useful luminescence from vacancy defects in refractory oxides for tunable lasers

A method of preparing a refractory oxide laser host material having high quantum efficiency, high thermal stability, and high useful luminescence in the nanoseconds range comprising the steps of:

• (a) removing substantially all of the hydrogen from a single crystal of said refractory oxide to a level of less than about 10.sup.13 protons/cm.sup.3 by the simultaneous steps of heating said crystal to a temperature sufficient to dissociate hydrogen from OH.sub.- bonds within said crystal and applying an electric field across said crystal to sweep the dissociated hydrogen ions from said crystal;
• (b) further heating said crystal in an atmosphere of a cation vapor of said refractory oxide at an elevated pressure and temperature sufficient to thermochemically reduce the oxygen content of said crystal to form oxygen (anion) vacancies within said crystal so that F.sup.+ luminescence is produced when said crystal is optically excited by light of a wavelength within the absorption band of said crystal, said temperature being sufficient to remove contaminants by means of outdiffusion during thermochemical reduction of the oxygen in said crystal, thereby preventing crystal darkening;
• and
• (c) irradiating said crystal with electrons sufficient to inactivate trace amounts of H.sup.- ions, thereby improving the ratio of short-lived to long-lived luminescence following optical excitation.