Xi X M, Weiss T, Wong G K L, Biancalana F, Barnett S M, Padgett M J, Russell P St J
Max Planck Institute for the Science of Light, Guenther-Scharowsky Strasse 1, 91058 Erlangen, Germany.
Max Planck Institute for the Science of Light, Guenther-Scharowsky Strasse 1, 91058 Erlangen, Germany and School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
Phys Rev Lett. 2013 Apr 5;110(14):143903. doi: 10.1103/PhysRevLett.110.143903. Epub 2013 Apr 4.
In this Letter we show that, in spectral regions where there are no orbital cladding resonances to cause transmission loss, the core mode of a continuously twisted photonic crystal fiber (PCF) exhibits optical activity, and that the magnitude of the associated circular birefringence increases linearly with twist rate and is highly reproducible. In contrast to previous work on twist-induced circular birefringence, PCF has zero linear birefringence and an on-axis core, making the appearance of circular birefringence rather unexpected. A theoretical model based on symmetry properties and perturbation theory is developed and used to show that both spin and orbital angular momentum play a role in this effect. It turns out that the degenerate left- and right-circularly polarized modes of the untwisted PCF are not 100% circularly polarized but carry a small amount of orbital angular momentum caused by the interaction between the core mode and the hollow channels.
在本信函中，我们表明，在不存在导致传输损耗的轨道包层共振的光谱区域中，连续扭曲的光子晶体光纤（PCF）的纤芯模式呈现出光学活性，并且相关圆双折射的大小随扭曲率线性增加且具有高度可重复性。与先前关于扭曲诱导圆双折射的工作不同，光子晶体光纤具有零线性双折射和轴向纤芯，这使得圆双折射的出现相当出乎意料。基于对称性和微扰理论开发了一个理论模型，并用于表明自旋和轨道角动量在这种效应中都起作用。结果表明，未扭曲的光子晶体光纤的简并左旋和右旋圆偏振模式并非100%圆偏振，而是由于纤芯模式与中空通道之间的相互作用而携带少量的轨道角动量。
