Twentyfold blue upconversion emission enhancement through thermal effects in Pr3+/Yb3+-codoped fluoroindate glasses excited at 1.064 mu m

Infrared-to-visible upconversion emission enhancement through thermal effec ts in Yb3+-sensitized Pr3+-doped fluoroindate glasses excited at 1.064 mu m is investigated. A twentyfold increase in the 485 nm blue emission intensi ty as the sample temperature was varied from 20 to 260 degrees C was observ ed. The visible upconversion fluorescence enhancement is ascribed to the te mperature dependent multiphonon-assisted anti-Stokes excitation of the ytte rbium sensitizer and excited-state absorption of the praseodymium acceptor. A model based upon conventional rate equations considering a temperature d ependent effective absorption cross section for the F-2(7/2)-->F-2(5/2) tra nsition of the Yb3+ and (1)G(4)-->P-3(0) excited-state absorption of the Pr 3+, agrees very well with the experimental results. (C) 2000 American Insti tute of Physics. [S0021-8979(00)08209-8].