2.3- and 4.4-μm Lasing in Cr, Fe:Zn_{1 –x}Mn_xSe (x = 0.3) Single Crystal Pumped by Q-Switched Er:YLF Laser at 1.73 μm

Abstract

Novel Cr²⁺ and Fe²⁺ co-doped Zn_1–xMn_xSe (x = 0.3) crystal with Cr²⁺ to Fe²⁺ ions concentration ratio of about 1 : 2 (both doping ions concentration were at the ~10¹⁸ cm^–3 level) with a good optical quality was synthesized. Under pumping by a Q-switched Er:YLF laser at 1.73 μm, the oscillations of Cr²⁺ ions at 2.3 μm as well as Fe²⁺ ions at 4.4 μm were realized. Both regimes, i.e. intracavity pumping of Fe²⁺ ions by Cr²⁺ ions as well as excitation through the Cr²⁺ → Fe²⁺ ions energy transfer mechanism, were demonstrated. The output energy for Cr²⁺ ions lasing at 2.3 μm was up to 900 μJ while Fe²⁺ ions lasing at 4.4 μm reached up to 60 μJ in the intracavity pumping mode. In the Cr²⁺ → Fe²⁺ energy transfer mode, the maximum output energy was 20 μJ at 4.4 μm. Laser generation at 2.3 μm was observed up to 340 K while Fe²⁺ ions oscillations stopped for temperatures above ~150 K. The Fe²⁺ ions oscillation wavelength was observed to shift with temperature increase from ~4.4 μm at 78 K to ~4.5 μm at 150 K. The Fe²⁺ ions output pulses were quite stable in amplitude and temporal domain in both excitation modes with beam profile close to the fundamental transversal mode.