论文标题
正常色散培养基中的掌光传播
Superluminal light propagation in a normal dispersive medium
论文作者
论文摘要
我们研究了通过分散原子培养基的拉瓜仪（LG）束的传播。我们局限于将较弱的探针场和三个强耦合场应用于媒介，这导致开发四级双$ V $ type原子系统。我们首先将所有三个强耦合场视为平面波，并计算探针LG场的组速度的分析表达式。看来，分散介质中的结果公式与自由空间的公式非常吻合。我们还发现了从光轴中探针LG场的组速度的更通用的分析表达，并将其投影与传播轴的投影进行比较。事实证明，这两个量在光轴，梁和雷利范围的光轴上相等。最后，我们假设强耦合场之一是LG场，并探索其轨道角动量（OAM）如何影响探针LG场的组速度。我们的分析预测了探针LG场的组速度的一种奇怪行为，以便它超过自由空间中的光速。 LG光束的这种异常传播是由于其螺旋相位前部的变形而导致平面和LG场的经典干扰。
We study the propagation of a Laguerre-Gaussian (LG) beam through a dispersive atomic medium. We restrict ourselves to applying a weak probe field and three strong coupling fields to the medium, which leads to developing a four-level double $V$-type atomic system. We first regard all the three strong coupling fields as the plane-waves and calculate an analytical expression for the group velocity of the probe LG field on the optical axis at the waist of the field. It appears that the resulting formula in a dispersive medium is in good agreement with that of the free space. We also find a more general analytical expression for the group velocity of the probe LG field out of the optical axis and compare with its projection onto the propagation axis. It is turned out that these two quantities are equal on the optical axis, at the waist of the beam and the Rayleigh range. Finally, we assume one of the strong coupling fields to be an LG field and explore how its orbital angular momentum (OAM) affects the group velocity of the probe LG field. Our analysis predicts a strange behavior for the group velocity of the probe LG field inside a normal dispersive medium so that it can exceed the speed of light in free space. Such an unusual propagation of the LG light beam results from the distortion of its helical phase front via the classical interference of the planar and LG fields.
