Second-Order Nonlinear Polarization in the Strong-Field Regime [article]

Liang Li, Tengfei Huang, Pengfei Lan, Yinfu Zhang, Jiapeng Li, Xiaosong Zhu, Lixin He, Wei Cao, Peixiang Lu
2020 arXiv   pre-print
We theoretically and experimentally investigate the second-harmonic generation (SHG) in a strong laser field. Our prototype experiment with ZnO demonstrates distinct anisotropic distributions of SHG yield, which deviate from the normal perturbation nonlinear optics theory. The experimental results show that the second-order nonlinear susceptibility is no longer a constant and it changes in the strong-field regime. The new features of SHG are due to the so far overlooked polarization induced by
more » ... trong-field tunneling. To reveal its effect, we propose a non-perturbation bond-charge model and a generalized second-order susceptibility (GSOS). Our work extends the normal second-order nonlinear responses from the perturbation to strong-field regime, and it suggests an all-optical approach to control the nonlinear optical properties of matter.
arXiv:2010.13298v1 fatcat:tdcqpvhg2bfnzfd7x2dgc6txdu