Chiral materials possess some unusual properties for which they have attracted tremendous interest in recent research. In this paper, we discuss the interaction of electromagnetic fields with an initially isotropic material, making it anisotropic chiral by inducing magnetoelectric cross coupling. We consider a four-level double $\Lambda$-type configuration of an atomic ensemble, which is simultaneously sensitive to relative phase of the applied fields due to its closed-loop nature, providing an extra degree of freedom for controlling the birefringent nature of the medium. We show that the material splits a linearly polarized probe field into left- (LCP) and right-circularly polarized (RCP) components, and their angular divergence can be related to the optical activity of the medium. This leads to efficient modulation of the probe field, which may be helpful in accurate position detection of the transmitted beams and images. Next, we demonstrate that such a medium can be used to couple incident light with surface plasmons (SPs) in two ways: (1) as a prism-like coupler, in either Otto- or Kretschmann-type geometry, where excitation of SPs can be achieved beyond a certain incident angle of the interacting pulse in a plasmonic waveguide placed closed to it; and (2) direct excitation of SPs by a LCP or RCP beam from the chiral medium in a particular slit-type plasmonic waveguide. We find that the coupled modes in the latter case are unidirectional and highly tunable. Further, we show that the birefringent nature of the medium as well as the plasmonic field intensities can be efficiently manipulated with a number of controlling parameters. Our results may find applications in image coding, plasmonic sensors, and bio-photonics.

中文翻译：

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电磁诱导手性介质的光学活性和表面等离激元极化子的激发

手性材料具有一些不同寻常的特性，因此在最近的研究中引起了极大的兴趣。在本文中，我们讨论了电磁场与初始各向同性材料的相互作用，并通过诱导磁电交叉耦合使其成为各向异性手性。我们考虑一个四级双$ \ Lambda $原子团的双键型构型，由于其闭环性质而同时对所施加场的相对相位敏感，为控制介质的双折射性质提供了额外的自由度。我们表明，该材料将线性偏振探测器场分为左（LCP）和右圆偏振（RCP）组件，并且它们的角度发散度可能与介质的光学活性有关。这导致探测场的有效调制，这可能有助于精确地检测透射光束和图像的位置。接下来，我们证明可以使用这种介质以两种方式将入射光与表面等离激元（SP）耦合：（1）作为Otto型或Kretschmann型几何形状的棱镜状耦合器，可以在靠近它的等离子体波导中，以超过相互作用脉冲的某个入射角的方式实现SP的激发；（2）通过LCP或RCP束从手性介质中的特定狭缝型等离子体波导中直接激发SP。我们发现，在后一种情况下，耦合模式是单向的且高度可调的。此外，我们表明可以通过许多控制参数有效地控制介质的双折射性质以及等离子体场强度。我们的结果可能会在图像编码，等离子传感器和生物光子学中找到应用。我们发现，在后一种情况下，耦合模式是单向的且高度可调的。此外，我们表明可以通过许多控制参数有效地控制介质的双折射性质以及等离子体场强度。我们的结果可能会在图像编码，等离子传感器和生物光子学中找到应用。我们发现，在后一种情况下，耦合模式是单向的且高度可调的。此外，我们表明可以通过许多控制参数有效地控制介质的双折射性质以及等离子体场强度。我们的结果可能会在图像编码，等离子传感器和生物光子学中找到应用。