Coherent control of vibrational wave packet in condensed matters using amplitude- and phase-programmable pulses

我们开发了全固态振幅和相位可编程飞秒光源。近变换限制脉冲从钛：蓝宝石种子激光器被传送到一个可编程的相位调制器。相位调制器由一对光栅和球面镜、液晶空间光调制器（LC-SLM）组成。从FROG测量中可以得到飞秒脉冲的时间分布和相位信息。测量到的相位信息在PC机中进行处理，并反馈给SLM进行相位掩模的调整。通过迭代调整，可以得到期望的相位图。利用相位可编程光源测量了一种菁染料分子的激发态居数。在激发态上的波包运动与啁啾方向和飞秒脉冲激发速率有关。激发态人口的强烈减少对菁染料分子中的负啁啾脉冲是有效的，这是用泵倾倒过程来解释的。我们对耦合到单振动模式的电子双能级系统进行了量子力学计算，并成功地再现了实验观察结果。

We developed all solid-state amplitude- and phase-programmable femtoseocnd optical source. Nearly transform-limited pulses from a Ti : sapphire seed laser is delivered into a programmable phase modulator. The phase modulator is composed of a pair of grating and spherical mirror, and liquid crystal spatial light modulator (LC-SLM). The temporal profile and phase information of the femtosecond pulses can be obtained from the FROG measurement. The measured phase information is processed in a PC and fed back to the SLM for adjustment of the phase mask. A desired phase pattern will be realized through the iterative adjustment.We measured excited-state population in a cyanine dye molecule using the phase programmable optical source. Wave packet motion on the excited-state was observed to be dependent on chirp direction and rate of excitation by femtosecond pulses. Strong reduction in excited state population is efficient for negatively chirped pulses in the cyanine dye molecule, which is explained in terms of a pump-dump process.We have performed a quantum mechanical calculation for an electronic two-level system coupled to a single vibrational mode, and successfully reproduced the experimental observation.