THERMAL SWITCHING OF LASER EMISSION OF Er3+ AT 2.69 μ AND Tm3+ AT 1.86 μ IN MIXED CRYSTALS OF CaF2:ErF3:TmF3

Abstract

Pronounced temperature‐dependent transfer of excitation from the Er³⁺ laser pump levels to lower levels of Er³⁺ was observed in CaF₂:ErF₃ single crystals at ErF₃ concentrations exceeding 12.5 wt %. Transfer of excitation from Er³⁺ to Tm³⁺ occurred when TmF₃ was included as a second active constituent of the crystals. Stimulated emission of the ⁴I_11/2 → ⁴I_13/2 transition of Er³⁺ at 2.69 μ at 298°K resulted independently of Tm³⁺ and as a consequence of concentration quenching of emission of Er³⁺ from levels above ⁴I_11/2. At 100°K reduced transfer of excitation to ⁴I_11/2 of Er³⁺ occurred due to radiative emission from levels above ⁴I_11/2, and laser emission of Tm³⁺ was detected at 1.86 μ.