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Radio-frequency sputtering fabrication of chalcogenide-based Er3+-doped vertical optical cavities for near-infrared operation

Chalcogenide-oxide Bragg reflectors and a 1-D vertical cavity for operation at 1.55 µm were designed and fabricated via radio-frequency sputtering. The Bragg reflectors were made out of repeating layers of Al2O3 and As2Se3, and the cavity was obtained via a Ga5Ge20Sb10S65:Er3+ defect layer. The layers’ properties were assessed via ellipsometry and SEM imaging. Transmission spectroscopy verifies the appearance of a well-defined stop-band centered around 1.5 µm with a very wide bandgap, and extremely low transmission, even with a relatively low layer count. The vertical optical cavity fabrication results in the appearance of a resonance within the band, at a wavelength corresponding to the 4I13/2→4I15/2 transition of erbium. The high transmittance at 808 and 980 nm allows for optical pumping, and thus light amplification and coherent light generation from the cavity. The operation of these devices was investigated, showing coherent light emission at 1.5 µm. The results are encouraging in assessing the viability of this design and these materials for operation in the near-infrared range, providing an important step towards the fabrication of chalcogenide-based optical amplifiers for the near-infrared.