Thermal shifts and electron–phonon coupling parameters of the R-lines for Cr3+ ion in Y3Al5O12 crystal

The thermal shifts of R-1- and R-2-lines of laser crystal Y3Al5O12 (YAG):Cr3+ are investigated by considering both the static contribution caused by lattice thermal expansion and the vibrational contribution due to electron-phonon interaction. The investigation is in terms of the analyses of pressure- and temperature-dependences of R-lines. The results show that (i) the new theoretical expression of thermal shift by including the above two contributions is almost the same as that containing only the vibrational contribution obtained in the previous papers when the parameter -alpha changes to A-alpha' (where alpha and alpha' are, respectively, the apparent and true electron-phonon coupling parameters and A is a parameter concerning the static contribution), and (ii) the static contribution to the thermal shifts of R-lines in sign is opposite to and in magnitude is about 20% of vibrational one. So the true electron-phonon coupling parameter alpha' increases by about 20% compared with the corresponding apparent one in YAG:Cr3+. It appears that to explain reasonably the thermal shift of spectral line and to obtain the true electron-phonon coupling parameter, the static contribution to the thermal shift should be taken into account. (c) 2012 Elsevier B.V. All rights reserved.