Li Hanxiao, Pan Shengzhe, Chen Fei, Sun Fenghao, Li Zhaohui, Xu Huailiang, Wu Jian
Opt Lett. 2020 Dec 15;45(24):6591-6594. doi: 10.1364/OL.410153.
Optical ionization of N and subsequent population redistribution among the ground and excited states of N2+ in an intense laser field are commonly accepted to be fundamentally responsible for the generation of N2+ lasing. By finely controlling this two-step process, the optimization of N2+ lasing is possibly achieved. Here, we design a waveform-controlled polarization-skewed (PS) pumping pulse, in which the leading and falling edges are orthogonally polarized, and their relative field strength and phase can be well controlled. We demonstrate that precise manipulation of the N2+ lasing at 391 nm and 428 nm emissions can be achieved by modulating both the relative phase and amplitudes of the two orthogonally polarized components of the pumping PS pulse. We find that the optimization of N2+ lasing depends not only on the competitive balance between the ionization and post-ionization coupling that varies in different pumping energies but also on the phase with the maximum intensity appearing at the phase of . Orders of magnitude enhancement in the N2+ lasing intensity is observed as the phase changes from (+1/2) to . The PS pulse with a controllable spatiotemporal waveform provides us a robust and straightforward tool to efficiently enhance the N2+ lasing emission.
在强激光场中，N的光电离以及随后N₂⁺基态和激发态之间的布居再分布通常被认为是N₂⁺激光产生的根本原因。通过精细控制这个两步过程，有可能实现N₂⁺激光的优化。在此，我们设计了一种波形控制的偏振倾斜（PS）泵浦脉冲，其前沿和后沿正交偏振，并且它们的相对场强和相位可以得到很好的控制。我们证明，通过调制泵浦PS脉冲的两个正交偏振分量的相对相位和幅度，可以实现对391 nm和428 nm发射处N₂⁺激光的精确操纵。我们发现，N₂⁺激光的优化不仅取决于在不同泵浦能量下变化的电离和电离后耦合之间的竞争平衡，还取决于在相位处出现最大强度的相位。当相位从(+1/2)变化到时，观察到N₂⁺激光强度增强了几个数量级。具有可控时空波形的PS脉冲为我们提供了一个强大而直接的工具，以有效地增强N₂⁺激光发射。
