Generating optical orbital angular momentum at visible wavelengths using a plasmonic metasurface
Generating optical orbital angular momentum at visible wavelengths using a plasmonic metasurface
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DOI：
10.1038/lsa.2014.48
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发表时间：
2014-05-01
影响因子：
19.4
通讯作者：
Boyd, Robert W.
中科院分区：
文献类型：
--
作者：
Karimi, Ebrahim;Schulz, Sebastian A.;Boyd, Robert W.
具有螺旋形相位波前的光束除了具有描述其偏振的自旋角动量之外，还具有沿其传播方向的轨道角动量沿着。直到最近，人们还认为光的这两种“旋转”运动在很大程度上是独立的，在光与物质的相互作用中不能耦合。然而，现在已知与精心设计的复杂介质的相互作用可以导致自旋-轨道耦合，其中自旋角动量的变化将修改轨道角动量，反之亦然。在这项工作中，我们提出并证明了等离子体纳米结构的双折射可以用来将圆偏振光转换为携带轨道角动量的光。在可见光波长下工作的设备是由亚波长等离子体纳米天线的空变阵列设计的。实验证实，通过该装置传输的圆偏振光具有+/- 2（h）/bar的轨道角动量（转换效率至少为1%）。这项技术为实现可集成到光谱学、纳米级传感和使用集成光子器件的经典或量子通信应用中的轨道角动量发生器铺平了道路。
Light beams with a helical phase-front possess orbital angular momentum along their direction of propagation in addition to the spin angular momentum that describes their polarisation. Until recently, it was thought that these two 'rotational' motions of light were largely independent and could not be coupled during light-matter interactions. However, it is now known that interactions with carefully designed complex media can result in spin-to-orbit coupling, where a change of the spin angular momentum will modify the orbital angular momentum and vice versa. In this work, we propose and demonstrate that the birefringence of plasmonic nanostructures can be wielded to transform circularly polarised light into light carrying orbital angular momentum. A device operating at visible wavelengths is designed from a space-variant array of subwavelength plasmonic nano-antennas. Experiment confirms that circularly polarised light transmitted through the device is imbued with orbital angular momentum of +/- 2 (h) over bar (with conversion efficiency of at least 1%). This technology paves the way towards ultrathin orbital angular momentum generators that could be integrated into applications for spectroscopy, nanoscale sensing and classical or quantum communications using integrated photonic devices.