The photoluminescence of Er3+in borosilicate glass is strongly enhanced by the presence of silver. Samples prepared by a combination of erbium ion implantation and Na+↔Ag+ ion exchange show an increase of the Er3+excitation efficiency of up to a factor 70 when excited at 488 nm. Excitation of Er3+ is possible over a broad wavelength range in the near ultraviolet and visible. Our data suggest that absorption of light occurs at a silver ion/atom pair or similar defect, followed by energy transfer to Er3+. We can exclude that silver nanocrystals are part of the dominant excitation mechanism, neither via local field enhancement effects due to their surface plasmon resonance nor via absorption and subsequent energy transfer to Er3+.

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We have used a rate equation propagation model of an Er3+/Yb3+ doped Al2O3 waveguide amplifier with copropagating pump at 980 nm to investigate the dependence of gain on Yb3+ concentration. The model includes excited state absorption and energy transfer upconversion processes within the Er3+ as well as the relevant energy transfer processes between Yb3+ and Er3+. The results of the calculations indicate a close relationship of the parameters gain, launched pump power, waveguide length, and Yb3+ concentration. Codoping with a well-chosen Yb3+ concentration is shown to increase the gain around 1530 nm for all combinations of these parameters. The gain is improved most by Yb3+ codoping at pump powers around the amplifier threshold. At high pump powers the increase in gain of an Er3+/Yb3+ doped waveguide is insignificant compared to that of its Er3+ doped counterpart. Furthermore for each launched pump power, a nonzero Yb3+ concentration can be determined, which maximizes the gain.

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