Room temperature iron doped II-VI lasers have demonstrated broad band tunability between 3.5 and 6 μm with efficiency ~40%. However, these lasers require pump sources with a wavelength ~3 μm which could be selected only from a few available. Cobalt ions in the II-VI materials have strong absorption bands at ⁴A₂→⁴T₁(⁴P) and ⁴A₂→⁴T₁(⁴F) transitions located at ~0.75 and 1.5 μm, respectively. A number of different laser sources (including diode lasers) could be potentially used for cobalt excitation followed by energy transfer to iron ions. Here we report materials fabrication and study of energy transfer in Co:Fe:ZnS(ZnSe) crystals. Iron-cobalt co-doped samples were prepared using a two-stage post-growth thermal diffusion procedure with Fe concentrations of 8.5-19x10¹⁸ cm^-3. Kinetics and photoluminescence spectra reveal energy transfer under cobalt excitation at ⁴A₂-⁴T₁(⁴F) transition by 1.56 μm radiation and ⁴A₂-⁴T₁(⁴P) transition by 0.7 μm radiation. Analysis shows effective energy transfer from ⁴T₁(⁴F), ⁴T₂ and ⁴T₁(⁴F) Co²⁺ energy levels to ⁵T₂ excited level of Fe²⁺ ions the first realization of Fe²⁺ ions lasing at 3.6 μm and 3.8μm via Co-Fe energy transfer. Demonstrated effective Co²⁺→Fe²⁺ energy transfer process could result in utilization of a more convenient laser pump sources for the Fe²⁺:II-VI lasers.

Date Published: 15 February 2012
PDF: 6 pages
Proc. SPIE 8235, Solid State Lasers XXI: Technology and Devices, 823503 (15 February 2012); doi: 10.1117/12.909287

Published in SPIE Proceedings Vol. 8235:
Solid State Lasers XXI: Technology and Devices
W. Andrew Clarkson; Ramesh K. Shori, Editor(s)