Chromim doped ZnSe is very promising material for optoelectronics (tunable lasing in Mid Infrared) and spintronics (high temperature ferromagnetism) applications.

In this communications two-color spectroscopy (pulse-to-probe) experiments are discussed. We show that two strong Cr²⁺ intra-shell emissions, the first at 930-1300 nm (with life time τ=1.8 ms) and the second at about 2200-2800 nm, can be efficiently pumped upon the Cr²⁺ → Cr⁺ photoionization transition. The intra-shell emission can be enchanced upon additional illumination with Free Electron Laser (FEL) with photon energy tuned at 0.08-0.14 eV range, as we demonstrate for the 930-1300 nm photoluminescence, for which we first present arguments for the Cr²⁺-centers relation. Enhancement of th intra-shell emissions we relate to ionization of shallow ZnSe acceptors, followed by capture of free holes by Cr⁺ ions. Hole capture by Cr⁺ centers proceeds via excited intra-shell states of Cr²⁺ ions, and thus is followed by two easily detectable Cr²⁺ intra-shell emissions, opening a simple method for detection of THz radiation for photon energies above 80 meV.