Large band gap materials are transparent to low intensity near-infrared (NIR) light. However, at sufficiently higher intensities, nonlinear absorption takes place by multi-photon processes and field assisted collisional ionization . Whereas for longer pulse durations (tp), tp > 100 fs, laser driven electrons can gain large kinetic energies by mechanisms such as inverse bremsstrahlung and electron avalanches , in short pulses, tp < 100 fs, these electrons are excited to the conduction band by multiphoton absorption. In order to study field dependent ionization processes, we will perform single-shot nonlinear transmission measurements at and beyond breakdown threshold of a transparent media such as fused silica and host matrices containing nanoparticles. This is enabled by indigenous instrumentation we developed at the femtosecond laser (fs) facility.
In the second part of this graduate work, we are currently investigating ZnO nanoparticles prepared by fs laser pulses . This study explores the dependence of the photoluminescence of the nanoparticles on different conditions of fs laser ablation. Further, we propose to continue this into a mature investigation exploring the physics and the applications. A combination of the two research themes presented here is envisaged in the form of ultrafast nonlinear transmission studies of nanoparticles synthesized by fs laser ablation.
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