The accumulation of femtosecond laser radiation energy in crystals of lithium fluoride

Abstract

We present the results of studies of energy accumulation during the non-destructive interaction of extremely intense near infrared laser radiation with model wide band gap dielectric crystals of lithium fluoride, when the intensity of pulses is sufficient for effective highly nonlinear absorption of light and for the excitation of the electron subsystem of matter and the energy of pulses is still not sufficient for significant heating, evaporation, laser breakdown or other destruction to occur. We studied the emission of energy in the form of light sum of thermally stimulated luminescence accumulated under conditions of self-focusing and multiple filamentation of femtosecond laser radiation. It was established that it's the F2 and F[3]{+} color centers and supplementary to them centers of interstitial type which accumulate energy under the action of a single femtosecond laser pulses. When irradiated by series of pulses the F3, F[3]{-} and F[4] centers additionally appear. F2 centers are the main centers of emission in the process of thermally stimulated luminescence of accumulated energy. The interstitial fluoride ions (I-centers) are the kinetic particles. They split off from the X[3]{-} centers in the result of thermal decomposition of latter on the I-centers and molecules X[2]{0}. I-centers recombine with F[3]{+} centers and form F[2] centers in excited state. The latter produce the characteristic emission spectrum emitted in the form of thermally stimulated luminescence.