Hydrogen passivation and microstructure fabrication in erbium silicates for optical amplification applications around 1.5 um (Conference Presentation)

Abstract

Erbium (Er) has offered a means towards optical amplification around 1.5 µm due to the intra-4f transitions of Er3+ ions. Er silicates are of much interest due to a 3 order increase in the concentration of Er3+ ions in the film as opposed to different Er-doped materials. Unfortunately, the major hindrance toward optical gains in such erbium containing materials is the fast quenching of Er luminescence, mainly resulting from excitation energy dissipation at structural defects even with a small density, via resonant energy transfer processes among Er ions. In this work, we investigate effects of hydrogen passivation and micro/nano scale structures on the luminescence properties of Er silicates. Arrays of micron-sized erbium silicate structures are created via etching a silicon wafer followed by deposition of erbium metal onto the etched pits. After deposition, the photoresist is removed through lift off and the metal structures are subjected to high temperature oxygen annealing (1200˚C) for oxidation of the film. Hydrogen passivation is conducted in a H2 gas ambient between 500˚C and 900˚C. Rutherford backscattering spectroscopy (RBS) and x-ray diffraction (XRD) are used to determine the composition and crystal structure information of the resultant thin films and photoluminescence (PL) is measured for their luminescence properties. The results show a significant decrease of photoluminescence in the ultraviolet/visible (UV/Vis) range, accompanied by an increase in both the intensity and lifetime of the near-infrared (NIR) luminescence emission around 1.5 µm wavelength from Er oxide/silicate compound thin films, following passivation in a H2 gas. Furthermore, samples with arrays of micro-structured Er silicates exhibit stronger NIR luminescence than the thin film sample. Combining with computer simulations, we identify the possible mechanisms for the observed Er luminescence enhancement, and suggest promising routes toward optical amplification around 1.5 µm in Er compounds.