Strong green emission from Er3+ in a fluorine containing (Pb, La)–tellurite glass without using up-conversion route

Absorption, emission, excitation spectra and the lifetime of the 4 S 3/2 excited luminescent state of Er 3+ ions in a fluorine containing (lead, lanthanum)-tellurite glass have been studied. The glass exhibits a strong green luminescence upon excitation through 380 nm ( 4 I 15/2 → 4 G 11/2 ) absorption band of its Er 3+ ions. The spectrum consists of a strong green component in the wavelength range 534-553 nm due to luminescence transitions 2 H 11/3 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 and a very weak red component in the range 650-710 nm due to 4 F 9/2 → 4 I 15/2 transition. The Stark split components of the 4 S 3/2 state are not very clear in the spectrum, but the biexponential luminescence decay of the 4 S 3/2 state confirms the presence of the Stark levels. A rapid conversion of the upper Stark level to the lower level is also evident from the decay kinetics which helps greater number of ions to populate in the lower stark level of the 4 S 3/2 state. Thus, the present study indicates that the glass may be a suitable candidate for use as a laser medium in making a solid state green laser by pumping the later by normal route.