Photoluminescence study of LiNbO 3 :Cr 3+ ; W 4+ at high pressure. Pressure dependence of spectroscopic parameters and local structure of Cr 3+

Abstract In this study, the photoluminescence properties of congruent codoped LiNbO3:Cr3+; W4+, crystals have been systematically investigated by performing photoluminescence studies at room temperature in the 0–280 kbar pressure range. In particular, we focus on the influence that hydrostatic pressure has on the 2E→ 4A2 (R-lines) transitions of Cr3+. It has been observed that the pressure dependence of the spectral position of the R-lines associated with both Cr3+ centres β and γ shows a bilinear behaviour with an abrupt slope change near 210 kbar. This change is related to the existence of a pressure-induced structural phase transition in the LiNbO3 host. The analysis of experimental results provides the Racah parameters B and C and the crystal field parameter 10Dq and their pressure and volume, through the crystal field theory and equation of state, dependences.