On The Excitonic Absorption Of CuCl Microcrystallites In A Glass Matrix Under High Resonant Excitation Conditions

Abstract

We present new experimental results concerning the optical nonlinearities of CuCl microcrystallites embedded in a glass matrix. Using a "pump and probe" technique, the induced absorption is measured in the spectral range of the Z3 exciton. We observe two phenomena: first, a bleaching of the excitonic resonance accompanied by the generation of a new absorption band at higher photon energies when the test probes the sample during the pump pulse; secondly, a weak shift of the excitonic resonance towards higher photon energies when probing the sample during and after the pump excitation. We vary the intensity and the photon energy of the pump beam as well as the delay between the pump and the probe pulses. Thus we can show that the pump beam populates excitonic states, which leads to a complete bleaching of the excitonic absorption. In addition, excitons can be created at higher energies, inducing the new absorption band. Its energy depends on the number of states already occupied in the microcrystallites. The shift of the excitonic resonance, on the contrary, can be explained by the heating of the microcrystallites through this high population of excitons and its non radiative decay during and after the excitation pulse.