Photoluminescence quenching in InP:Yb with a free-electron laser

We have studied photoluminescence (PL) from Yb3+ ions in InP, which is observed after a band-to-band excitation with a Nd:YAG laser. Upon irradiation of this system with a powerful mid-infrared beam from a free-electron laser (FEL), the PL is quenched. Measurements of the dependence of this effect on the wavelength of the FEL reveal a discontinuity, corresponding to the photon energy needed to reverse the excitation process. This proves the existence of an intermediate step in the excitation process, as postulated in models of excitation. For the quenching observed in the wavelength region where the photon energy of the FEL is not sufficient for this one photon energy back-transfer, two mechanisms are considered to explain the measured behavior. It is shown that a free-hole Auger quenching is the most likely mechanism to occur, and the Auger coefficient for this process is determined.