EFFECT OF YB3+-CODOPING ON THE UP-CONVERSION EMISSION INTENSITY IN ER3+-DOPED ZBLAN FLUORIDE CLASSES UNDER 800-NM EXCITATION

The effect of Yb3+-codoping on the upconversion emission intensity in Er3+-doped ZBLAN fluoride glasses is investigated. The codoping of Yb enhanced the emission intensity for the samples excited by an 800-nm laser diode beam. The enhancement in a constant YbF3 content (2 mol%) increased with increasing ErF3 content was about 70% of the initial value at 550 nm for the glasses containing 8 mol% of ErF3. The emission intensity at 550 nm in a constant ErF3 content (5 mol%) increased remarkably with the addition of YbF3 and was maximized around 7 mol% of YbF3 content, giving an increased ratio of about 200% of the initial value. The reason for the enhancement is discussed and it is derived mainly from two-step excitation of Er3+ assisted by Yb3+ excited through the energy transfer from Er3+.