800-nm upconversion emission in Yb-sensitized Tm-doped optical fiber

We report, for the first time, the upconversion emission at 800 nm in Yb-sensitized Tm-doped alumino-germano-silicate glass optical fiber when pumped with the 980-nm laser diode. Maximum gain of 6 dB was measured at 808 nm and the upconversion is contributed to the energy transfer from Yb/sup 3+/ ions to Tm/sup 3+/ ions.