Mid-IR lasing of Fe²⁺ ions via Cr²⁺ → Fe²⁺ energy transfer process with YLF:Er or laser diode pumping at 1.7 µm

A nonradiative Cr²⁺ → Fe²⁺ ions energy transfer process in Zn_1-xMn_xSe:Cr²⁺,Fe²⁺ (x = 0.05) single crystal with a Cr²⁺ to Fe²⁺ ions concentration ratio about 2.5:1 was investigated under short-pulse (200 ns) ∼1.73 µm excitation by YLF:Er laser. Fe²⁺ ions lasing in a temperature range from 78 K up to 200 K was achieved and the central oscillation wavelength was observed to increase from 4.1 µm to 4.4 µm, depending on the temperature of the active medium. Moreover, stable Fe²⁺ ions lasing under a “long” pulse excitation (1 ms, 10 Hz) by a ∼1.71 µm laser diode were demonstrated. The laser generated in a temperature range from 78 K up to 110 K at a central wavelength around ∼4.17 µm. The maximum mean laser output power of 4.1 mW with a slope efficiency of 2.3% with respect to the absorbed power was achieved. These results present a new possibility to develop a simple and compact diode-pumped coherent mid-infrared (4.1–4.3 µm) laser sources.