Electron-phonon coupling effects on Yb3+ spectra in several laser crystals

The complex absorption spectra of Yb3+ in YAG, LiNbO3 and YLF, three import ant laser crystals, are analysed in terms of electron-phonon coupling effec ts. The local symmetry for Yb3+ in these crystals is noncentrosymmetric all owing the coexistence of several electron-phonon coupling mechanisms in the formation of vibronic spectra. The shape of several Yb3+ absorption lines is interpreted in terms of the near resonant electron-phonon coupling theor y. The computer modelling, by taking into account more phonons in the reson ance region enables the assignment of crystal-held levels of the Yb3+ F-2(5 /2) multiplet and an estimation of electron-phonon coupling strengths. The phonons involved in the near resonance processes were observed in Raman spe ctra too. For YAG the modelling with a phonon density with four peaks in th e near resonant region is made and it gives a good description of the compl ex experimental pattern. In the case of Yb3+ in LiNbO3 and YLF the use of p olarization data evidences also the symmetry characteristics of the electro n-phonon coupling.