Polarons generated by laser pulses in doped LiNbO3 -: art. no. 125128

The temporal behavior of polarons generated by pulsed illumination of LiNbO3 crystals doped with Fe, Fe+Ti, and Cu is examined by detecting the light-induced absorption α(li) in a pump-probe experiment. The decay of the polarons is satisfactorily described by a stretched exponential function over a temporal range of six decades. This fact is attributed to the dependence of the polaron lifetime on the distance to the nearest deep traps or to the disorder in LiNbO3. The dependence of the amplitude and dynamics of the light-induced absorption on the pump intensity are explained within the framework of these models. The wavelength dependence of α(li) displays a maximum at about 740 nm, revealing the optical excitation of small bound Nb-Li(4+) polarons. Temperature-dependent measurements in the range 293-473 K reveal an Arrhenius behavior with an activation energy of about E-A=0.38 eV.