Søren Hanghøj Møller

LADIE: Laser amplification in exicted dielectrics – a new phenomenon

Supervisor: Peter Balling

Date student colloquium: 27/2/2017

Wide band gap materials (dielectrics) are under normal circumstances transparent to visible light. However, when exposed to intense, ultrashort laser pulses, the strong electric field perturbs the material significantly, thus allowing for a cascade of non-linear processes such as multiphoton absorption whereby a multitude of electrons are excited to the conduction band. The dielectric then becomes metal-like. The striking changes in material properties can be observed in time in pump-probe experiments where a strong pump pulse excites the material and a weak probe pulse, delayed in time, “feels” the response due to the pump. In this talk I will introduce a recent pump-probe experiment, which observed significant amplification of the probe pulse. This is an entirely new phenomenon, that has yet to be understood. I will introduce the basics of the physics behind the experiment, discuss some of the results and provide a possible explanation. The talk is based on an upcoming paper, which is a joint work between groups in Kassel and Aarhus.