Cooperative emission in Yb3+:YAG planar epitaxial waveguides

Blue emission was observed in Yb3+ activated YAG planar waveguides obtained by the liquid phase epitaxy on YAG substrates and in bulk Yb3+ : YAG crystals under infrared excitation. Through the excitation and emission spectra, decay time measurements and excitation intensity dependence the process responsible for this anti-Stokes emission was assigned to the cooperative deexcitation of two Yb3+ ions. Theoretical cooperative emission spectrum and the cooperative luminescence rate of Yb3+ : YAG waveguide were calculated.