Optical properties and upconversions in Er3+ doped Li:TeO2 glass

A NIR excitation of Er3+ doped Lithium modified tellurite (Li:TeO2) glass results in antistokes fluorescent emission near 380, 530, 551 and 654 nm (ultraviolet, green and red regions) in addition to NIR Stokes emission. The antistokes emissions are ascribed to transition from the excited 4G11/2, 4S3/2(2H11/2) and 4F9/2 levels in Er3+. The excitation involves three and two incident photons. On excitation with the green laser line at 532 nm also leads to similar emissions. The mechanisms involved in these processes are discussed on the basis of the known energy level diagram and the upconversion efficiency has been calculated. Lifetime of the 4S3/2 level has been measured. The temperature dependence of the upconversion process has also been investigated.