Mofared Mohammad, Irani Elnaz, Sadighi-Bonabi Rasoul
Department of Physics, Sharif University of Technology, P.O. Box 11365-9567, Tehran, Iran.
Phys Chem Chem Phys. 2019 May 8;21(18):9302-9309. doi: 10.1039/c8cp07619g.
Enhanced high harmonics are generated by local and global optimization approaches to achieve a supercontinuum spectrum. Based on time-dependent density functional theory calculations, the optimum convolution of a two-color chirped pulse from an N2O molecule implements a significant enhancement of cutoff frequency and high harmonic yield. The optimization is done by controlling the effective chirp parameters and the carrier-envelope phase of the designed laser field. Indeed, all of the effective parameters are adjusted simultaneously for the global optimization; whereas, just two variables are tuned to obtain the desired cutoff frequency based on the local optimization. The results show that the global optimization approach extends the cutoff frequency by 96% compared to the single-color field, which could produce an isolated 25 as output pulse. This method opens up a valuable route by a pulse shaping mechanism for the control of high harmonic generation and ultrafast measurements for reducing the computational time and repeatability of an experiment with high accuracy.
通过局部和全局优化方法产生增强的高次谐波，以实现超连续谱。基于含时密度泛函理论计算，来自N2O分子的双色啁啾脉冲的最佳卷积实现了截止频率和高次谐波产率的显著增强。通过控制设计激光场的有效啁啾参数和载波包络相位来进行优化。实际上，为了全局优化，所有有效参数会同时进行调整；而基于局部优化，只需调整两个变量就能获得所需的截止频率。结果表明，与单色场相比，全局优化方法将截止频率提高了96%，单色场可产生孤立的25as输出脉冲。该方法通过脉冲整形机制为控制高次谐波产生和超快测量开辟了一条有价值的途径，可减少实验的计算时间并实现高精度的可重复性。
