Abstract
Ultraviolet-blue upconversion (UC) radiations of ions at 240, 290, 360, 385, 418, 445, were observed in hexagonal powders under diode laser excitation of . UC mechanism analyses illustrate that successive energy transfers from to generate emissions at 240, 360, 385, and , while cross relaxations between ions evoke UC emissions at 290 and . Power dependence analyses indicate that these UC emissions already have intense saturation effects even at low-power density range of . Theoretical calculations based on steady-state equations demonstrate the proposed UC mechanisms and explain well the observed saturation effects.
© 2010 Optical Society of America
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