Ultrafast Phenomena

Time-resloved pump-probe experiment is a useful tool in studying the dynamics related to electrons, phonons, and spin. The basic analogy of IR pump-probe method is simple that a powerful light pulse, usulally labeled the 'pump pulse' of 'excitation pulse', interacts with the sample and excites it into a non-equilibrium state. The sample thereafter relaxes towards a new equilibrium state. This process can be mapped by sending a second much weaker pulse, 'probe pulse', onto a sample. The 'probe pulse' detects a change of optical properties without disturbing the object under investigation. Left figure shows simple scheme of this technique.