UP-CONVERSION OF RED-LIGHT INTO BLUE-LIGHT IN THULIUM DOPED FLUOROZIRCONATE GLASSES

Up-conversion of red light with a wavelength of about 650 nm in Tm3+ doped fluorozirconate glasses results in blue light. This blue light consists of two emission bands; one at 450 nm which is ascribed to the 1D2 --> H-3(4) transition, the other at 475 nm is ascribed to the 1G4 --> H-3(6) transition. The emission intensities of both bands vary quadratically with the excitation power. The up-conversion mechanism for these bands are elucidated from the results of the (up-conversion) emission and excitation spectra and decay time measurements of fluoride glasses with different Tm3+ concentrations. For glasses with a Tm3+ concentration of 0.2 mol% and greater, cross-relaxation processes occur which seriously decrease the up-conversion efficiency. These cross-relaxation processes turn out to be very efficient in Tm3+ doped fluoride glasses.