Single-Nanosecond-Pulse Lasing in Heavily Doped Fe:ZnSe

We investigated room-temperature pulsed lasing in heavily doped Fe:ZnSe single crystals. The active elements were pumped by a Q-switched Cr³⁺:Yb³⁺:Ho³⁺:YSGG laser operating at 2.87 μm. Our results show that the generation of short laser pulses has a deep high-frequency modulation associated with relaxation dynamics in Fe:ZnSe. The lasing regime obtained in this study provides a straightforward way to generate mid-IR single nanosecond pulses at moderate pump energies. Moreover, we found a relation between the lasing pulse duration and the concentration of Fe²⁺ doping ions, and we experimentally demonstrated pulse shortening in heavily doped active crystals. Single-pulse lasing with an FWHM pulse duration of ∼2.8 ns was achieved in ZnSe crystals doped with 2.3 · 10¹⁹ cm^-3 Fe²⁺ ions. The demonstrated single-pulse lasing regime is applicable for seeding high-power mid-IR laser systems.