Abstract

Upconversion emissions of Ho³⁺ ion sensitized by Yb³⁺ ion in fluoride glasses with different phonon frequencies were investigated. The green emission of 543nm is stronger in a fluorozircoaluminate glass (AZF) than in a fluorozirconate glass (ZBLAN). It suggests that the emission is primarily governed by the Yb³⁺-Ho³⁺ energy transfer rate rather than by the multiphonon decay rate of the emitting level. The concentrations of Ho³⁺ and Yb³⁺ were determined to provide higher emission efficiencies. Using fibers made of a AZF glass optimized in the dopant concentrations, gains were measured at 543nm with Тi:Аl₂O₃ laser pumping at 974nm. A maximum gain obtained for a 2mm fiber was 0.5dB for 90mW incident power. By tuning a pump wavelength, strong blue upconversion emissions were firstly, to our knowledge, observed in the Ho³⁺-Yb³⁺ system.

© 1993 Optical Society of America