Femtosecond Pulse Shaping And Its Application To Coherent Control

Quantum coherent control is a hot and developing field, and it can be used to manipulate the dynamical processes by laser pulse-shaping technique based on the quantum interference in the time or frequency domain and achieve the desirable outcomes. Optimal feedback control based on pulse-shaping technique has been widely applied in physical, chemical and biological processes, such as manipulation of vibrational dynamics in diatomics, one and two photon transition in atoms, molecular electronic population transfer, chemical reaction product branching ratios, and so on. So, it is of practice to investigate optimal feedback control and quantum coherent control. In this thesis, femtosecond pulse shaping was investigated based on Genetic algorithms (GA), and two-photon fluorescence and coherent anti-Stokes Raman scattering (CARS) are coherently enhanced.1) The theory of quantum coherent control and laser pulse shaping technique is introduced, and optimal feedback pulse shaping experimental system is established using LC-SLM and CCD detector, and optimal feedback control program is composed by Labview and C languages based on improved Genetic algorithms (GA).2) Using optimal feedback pulse shaping experimental system, optimal feedback control of two-photon transitions in molecular system (DCM (4-dicyanomethylene-2-methyl-6-p-dimethylaminostryryl-4H-pyran)) is demonstrated experimentally. The two-photon fluorescence of the DCM ethanol solution is enhanced by a factor of ~23%. The SHG-FROG trace indicates that the effective population transfer arises from the positively chirped pulse. The experimental results appear the potential applications in molecular physics.3) Using optimal feedback pulse shaping experimental system, the CARS signal can coherently be enhanced by a factor of ~7.1, SHG-FROG trace indicates that the CARS can be enhanced by the counterintuitive and compressed pulses.