Improved efficiency of planar light converters based on Al2O3-YAG:Ce eutectic crystals: Physical Trends and Limits.

A theoretical model of a crystalline converter of white light with internal scattering medium is proposed. Obtained are the expressions for estimation of the light converter efficiency depending on its optical parameters (refractive index and coefficients of absorption at the wavelengths of the incident and re-emitted light), as well as on the geometrical dimensions and the scattering indicatrix of the optical system. The physical limits of improvement of the converter efficiency due to strong internal scattering, are established. Realized are the theoretical and experimental estimations of the efficiency of the light converter based on the crystals of Al2O3-YAG:Ce eutectic alloy which amounts to 16%. This is twice as high in comparison with the efficiency of the light converter based on YAG:Ce single crystal.