Temperature response of the whispering gallery mode resonances from the green upconversion emission of an Er3+–Yb3+ co-doped microsphere

Abstract

Whispering gallery mode resonances lying in the green emission from an Er3+–Yb3+ co-doped glass microsphere have been analyzed under different temperatures in the range 290–380 K. Exciting the microsphere at 997 nm results in an upconversion emission with broad bands centered at 530 and 550 nm and overlapped resonances due to the spherical cavity. Both the band shape and the position of the resonances are temperature dependent which allow the correlation of the positions with the temperature inferred by the fluorescence intensity ratio technique. A resonances shift of 4.7 pm K−1 is achieved by laser heating in the power range 50–300 mW. The minimum temperature resolution has been found to be 0.7 K in the fluorescence intensity ratio technique and 100 times smaller for the whispering gallery mode shifts.