We demonstrate theoretically that an efficient field-free molecular orientation of LiH molecule steered by a few-cycle nonlinearly chirped laser pulse with frequency in the terahertz regime can be achieved. The frequency modulation parameter plays an important role in the molecular orientation, the maximum molecular orientation is and the orientation duration is 150 fs when . In the range of electric-field peak intensity MV/cm, we can find the maximum orientation degree in both positive and negative directions. Compared to the scheme steered by a normal laser pulse, we can find that a more efficient molecular orientation and a smaller difference in population between the adjacent states can be realized by using the nonlinearly chirped laser pulse under the same near-single-period conditions. In addition, at the same temperature, a higher molecular orientation and a smaller decrease rate of orientation with temperature can be obtained by the nonlinearly chirped laser pulse.

中文翻译：

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由几个周期非线性啁啾脉冲控制的 7LiH 无场定向

我们从理论上证明，通过频率为太赫兹范围的几周期非线性啁啾激光脉冲可以实现 LiH 分子的有效无场分子取向。调频参数对分子取向起着重要作用，当 时，分子取向最大为 ，取向持续时间为 150 fs 。在电场峰值强度MV/cm范围内，我们可以找到正负两个方向的最大取向度。与普通激光脉冲引导的方案相比，我们可以发现，在相同的近单周期条件下，使用非线性啁啾激光脉冲可以实现更有效的分子取向和相邻态之间较小的布居差异。此外，在相同温度下，非线性啁啾激光脉冲可以获得更高的分子取向和更小的取向随温度下降的速率。