Atomic layer deposition was used in preparing erbium (Er)-doped waveguides. Ridge-type Er-doped Al2O3 waveguides were patterned on silica-coated silicon wafers using photolithography and wet etching. Optical absorption, emission, fluorescence lifetime, and signal enhancement measurements were performed. Polarization dependence of the absorption spectrum and birefringence of the waveguide were measured. The material showed strong absorption and wide emission spectrum around 1530 nm with full-width at half-maximum of 52 nm. Signal enhancement of 6 dB was measured for a 3.9-cm-long waveguide.
Solehmainen, K., Kapulainen, M., Heimala, P., & Polamo, K. (2004). Erbium-doped waveguides fabricated with atomic layer deposition method. IEEE Photonics Technology Letters, 16(1), 194 - 196. https://doi.org/10.1109/LPT.2003.820484