Energy-transfer upconversion in $Al_2O_3:Er^{3+}$ thin layers


Wörhoff, K. and Bradley, J.D.B. and Agazzi, L. and Geskus, D. and Ay, F. and Kahn, A. and Scheife, H. and Petermann, K. and Huber, G. and Pollnau, M. (2008) Energy-transfer upconversion in $Al_2O_3:Er^{3+}$ thin layers. In: Second International Workshop on Advanced Spectroscopy and Optical Materials, 13-17 July 2008, Gdansk, Poland.

Abstract:Erbium-doped aluminum oxide (Al2O3:Er) is a promising material for integrated amplifier or tunable laser applications due to its wide gain spectrum around 1550 nm. We deposited Al2O3 layers on thermally oxidized Si-wafers by reactive co-sputtering at 550°C. Propagation losses were 0.11 dB/cm at λ =1.5 μm. Channel waveguides were fabricated by reactive ion etching with propagation losses down to 0.21 dB/cm. Under pumping at 977 nm, the optical small-signal gain at 1533 nm is 0.84 dB/cm, resulting in 5.4 dB net gain over the waveguide length of 6.4 cm. Net gain is obtained over a wavelength range of 41 nm.
The Er concentration was measured using Rutherford Back-Scattering (RBS). Lifetimes of the 4I13/2 level of up to 7 ms were measured for Er concentrations around 2×1020 cm-3. A faster decay with an increasingly non-exponential initial component is measured for higher Er concentrations (Fig. 2). While the initial quenching is probably due to migration-accelerated energy-transfer upconversion between neighboring Er3+ ions in the 4I13/2 level, the decreasing exponential tail is due to either pair-induced energy-transfer upconversion or quenching by impurity ions. Detailed investigations of the quenching mechanisms are currently under way.
Item Type:Conference or Workshop Item
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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