Conversion of infrared radiation into red emission in YVO4:Yb,Ho

Upon continuous wave excitation around 1 mum, a YVO4 crystal codoped with ytterbium and holmium exhibits intense red emission originating in the F-5(5) level and considerably weaker green emission originating in the S-5(2) level of Ho3+. The ratio of the red to green emission intensities is 17:1 at 300 K. The dependence of the intensity of both emissions on the pump power is nearly the same but the mechanisms determined on the basis of short pulse excitation are found to be different. It is concluded that the green emission is excited by two consecutive energy transfers from Yb3+ to Ho3+, whereas excited state absorption is involved in the excitation of red emission. (C) 2001 American Institute of Physics.