Upconversion studies in Tm, Ho co-doped alumino-zirco-fluoride glass

Tm, Ho co-doped alumino-zirco-fluoride (AZF) glass is an attractive candidate for an optical pre-amplifier around two microns. In Tm, Ho doped materials, however, upconversion from the upper laser levels of Tm /sup 3/F/sub 4/ and Ho /sup 5/I/sub 7/ occurs which reduces the gain coefficient and efficiency. Therefore it is important to determine the upconversion rate constants in order to estimate optimum performance of such a Tm, Ho: AZF glass pre-amplifier. In this work, the upconversion rate constants were determined under high average power pumping conditions by measuring gain coefficients and an appropriate comparison made from a simple rate equation model.