Optical nonlinearity in Ar and N2 near the ionization threshold.
Optical nonlinearity in Ar and N2 near the ionization threshold.
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DOI：
10.1103/physrevlett.107.103901
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发表时间：
2011-05
影响因子：
8.6
通讯作者：
J. Wahlstrand;Yu-Hsiang Cheng;Yu-hsin Chen;H. Milchberg
中科院分区：
文献类型：
--
作者：
J. Wahlstrand;Yu-Hsiang Cheng;Yu-hsin Chen;H. Milchberg
我们直接测量了氩和氮在薄气体靶中对电离阈值附近激光强度的非线性光学响应。与先前的测量[Opt.Express 17，13429（2009）]和计算[Phys.Rev.Lett. 106，183902（2011）]。此外，我们能够干净地分离氮气中的非线性响应的瞬时和旋转分量。在Ar和N2中，峰值瞬时折射率响应与激光强度成线性比例，直到电离点，于是响应突然变成负的并且是恒定的，与等离子体产生一致。
We directly measure the nonlinear optical response in argon and nitrogen in a thin gas target to laser intensities near the ionization threshold. No instantaneous negative nonlinear refractive index is observed, nor is saturation, in contrast with a previous measurement [Opt. Express 17, 13429 (2009)] and calculations [Phys. Rev. Lett. 106, 183902 (2011)]. In addition, we are able to cleanly separate the instantaneous and rotational components of the nonlinear response in nitrogen. In both Ar and N2, the peak instantaneous index response scales linearly with the laser intensity until the point of ionization, whereupon the response turns abruptly negative and ∼constant, consistent with plasma generation.