Numerical and experimental investigation of near-infrared-visible luminescence in erbium doped sol-gel SiO2

Erbium doped silicon dioxide (Er³⁺: SiO₂) was obtained by the sol-gel method. Efficient green and red upconversion luminescence was observed using 488 nm (70 mW, continuous wave) and 800 nm (25 ns pulsed) excitation. Upconversion study of luminescence was done for 3 different samples (1%, 4%, 10%: Er³⁺) of sol-gel SiO₂. A theoretical analysis was performed and the results obtained were compared with the experimentally recorded photoluminescence spectra. An evolutionary algorithm was employed for optimising the upconversion coefficients of the rate equations model while the lifetime values were obtained from the Judd-Ofelt analysis. The modelling results closely reproduce the experimentally observed spectra.