Optical properties of chromium (III) in MIIn(WO4)2hosts, where MI= Li, Na, K, Rb

Optical absorption, excitation and emission spectra have been measured for double indium tungstate crystals with the formula MICrxIn1−x(WO4)2 (x = 0.5–2%, MI = Li, Na, K and Rb) at temperatures ranging from 5 to 300 K. The broadband 4T2–4A2 luminescence from low-crystal-field Cr3+ sites was observed in all the crystals that were studied. The local structure of the Cr3+ surroundings is discussed in terms of the spectroscopic results, and the crystal field parameters, Dq, B and C of the Cr3+ ion are derived for all the materials. The Huang–Rhys parameters, S, and breathing phonons, , are reported. The reported data indicate a possible phase transition at about 150 K for the trigonal RbIn(WO4)2 chromium (III) doped crystals. The possible application of these crystals as laser systems is discussed.