Mid-IR lasing of iron-cobalt co-doped ZnS(Se) crystals via Co-Fe energy transfer

► Energy transfer in Fe and Co co-doped ZnS and ZnSe crystals. ► Mid-IR Fe2+photoluminescence results from Co2+ excitation at 4A2-4T1 transition. ► Fe2+ lasing in Co:Fe:ZnS crystal via energy transfer process was demonstrated.