Hollow core fibers for optical amplification

Hollow core optical fibers are normally passive light transport components. In contrast, within this Letter, we numerically investigate the possibility of using them as optical amplifiers, through the adoption of a novel fiber structure. We show that optical amplification can be achieved in hollow core fibers, where the cladding region is partially doped and composed of both resonant and anti-resonant elements. A balance between loss and glass/ optical mode overlap is obtained, which allows efficient amplification over a limited spectral bandwidth. We discuss the case of a thulium-doped optical amplifier based on this novel technological approach.