Optical and EPR spectroscopy of Zn:Cr:ZnSe and Zn:Fe:ZnSe crystals

• Strong bleaching of the divalent state of chromium and iron metals was studied.
• The IR luminescence quantum yield was measured under photo-ionization excitation.
• Excitation rate of the upper laser level under ionization transition was studied.
• Cr charge transfer processes were studied using time-dependent photo-EPR method.

Optical and EPR characterization of Cr and Fe doped ZnSe crystals annealed in Zn vapor revealed a strong bleaching of the divalent state of transition metal ions. Photo induced EPR kinetics were studied in 20–80 K temperature range. Analysis of time-dependent data reveals Cr1+ signal rise time decreases with increasing temperature. The non-exponential decay of Cr1+ concentration were analyzed using Auger-type recombination process. The photoluminescence quantum yield of Cr2+ ions at 5E(D) → 5T2(D) mid-IR transition excited via chromium ionization process was measured to be close to 100%.