Exciton-erbium energy transfer in si nanocrystal-doped SiO2

Silicon nanocrystals were formed in SiO2 using Si ion implantation followed by thermal annealing. The nanocrystal-doped SiO2 layer was implanted with Er to peak concentrations ranging from 0.015 to 1.8 at.%. Upon 458 nm excit ation, a broad nanocrystal-related luminescence spectrum centered around 75 0 nm and two sharp Er luminescence lines at 982 and 1536 nm an observed. By measuring the temperature-dependent intensities and luminescence dynamics at a fixed Er concentration, and by measuring the Er concentration dependen ce of the nanocrystal and Er photoluminescence intensity, the nanocrystal e xcitation rate, the Er excitation and decay rate, and the Er saturation wit h pump power we conclude that: (1) the Er is excited by excitons recombinin g within Si nanocrystals through a strong coupling mechanism; (2) the excit on-Er energy transfer rate is > 10(6) s(-1); (3) the exciton-Er energy tran sfer efficiency is > 60 %; (4) each nanocrystal can have at most similar to 1-2 excited Er ions in its vicinity, which is attributed to either an Ange r de-excitation or a pair-induced quenching mechanism; (5) at a typical nan ocrystal concentration of 10(19) cm(-3), the maximum optical gain at 1.54 m um of an Er-doped waveguide amplifier based on Si nanocrystal-doped SiO2 is similar to 0.6 dB cm(-1); (6) the effective Er excitation cross-section us ing this nanocrystal sensitization scheme is sigma (eff) approximate to 10( -15) cm(2) at 458 nm, which is a factor 10(5)-10(6) larger than the cross-s ection for direct optical pumping of Er. This enables the fabrication of an Er-doped nanocrystal waveguide amplifier that can be pumped using a white light source. (C) 2001 Elsevier Science S.A. All rights reserved.