Sensitization of the Ho3+ luminescence by Tm3+ or Cr4+ in Ca2Al2SiO8 crystals

摘要

Ho$-3$PLU$/ ions emitting in the near IR range, can be sensitized either by Tm$+3$PLU$/ or by Cr$+4$PLU$/ ions, as energy resonances between these ions are possible. In the Cs$-2$/Al$-2$/SiO$-7$/ (CAS) host, the shortest distance between two RI$+3$PLU$/ cations is 3.56 angstrom while this distance could be reduced to 3.14 angstrom when Cr$+4$PLU$/ and RE$+3$PLU$/ ions are considered. In this study, the materials are prepared in the form of small single crystal by the melting zone process in order to perform spectroscopic investigation. In the CAS host, the energy transfer processes are in competition with the very efficient non radiative multiphonon relaxation. Strong Tm $YLD Ho energy transfer enhanced the Ho$+3$PLU$/ near IR emission around 2 $mu@m while the Ho $YLD Tm back transfer probability is quite low. For Cr$+4$PLU$/:CAS, due to a strong electron-phonon coupling, Cr$+4$PLU$/ emission suffers from strong thermal quenching and almost vanished at room temperature. In the Cr$+4$PLU$/:RE$+3$PLU$/:Ca$-2$/Al$- 2$/SiO$-7$/ crystals, interactions between Cr$+4$PLU$/ and Er$+3$PLU$/, Ho$+3$PLU$/ or Tm$+3$PLU$/ occur and lifetime measurements are used to quantify the energy transfers probabilities.