Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological charges
Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological charges
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DOI：
10.1063/1.4895620
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发表时间：
2014-09-08
影响因子：
4
通讯作者：
Boyd, Robert W.
中科院分区：
文献类型：
--
作者：
Bouchard, Frederic;De Leon, Israel;Boyd, Robert W.
与光束的螺旋相位波前相关的轨道角动量为经典和量子通信提供了无限的“空间”。在产生和操纵光的轨道角动量状态的不同方法中，自旋和轨道角动量之间的耦合允许更快地操纵轨道角动量状态，因为它取决于操纵光的偏振状态，这比操纵传统的轨道角动量发生器更简单并且通常更快。在这项工作中，我们设计和制造了一个超薄的自旋到轨道角动量转换器，基于等离子体纳米天线，并在可见光波长范围内工作，能够将自旋转换为任意值的轨道角动量l。纳米天线在波束的横向平面中以具有明确定义的几何形状的阵列排列，具有特定的整数或半整数拓扑电荷q。当圆偏振光束穿过该超颖表面时，输出光束偏振切换旋向性，并且轨道角动量的值改变l = +/-2q（h）/bar/光子。我们的实验表明，l值范围从+/- 1到+/- 25，转换效率为8.6% +/-60.4%。我们的超薄器件是可集成的，因此适用于量子通信、量子计算和纳米级传感。(C)2014 AIP Publishing LLC.
Orbital angular momentum associated with the helical phase-front of optical beams provides an unbounded "space" for both classical and quantum communications. Among the different approaches to generate and manipulate orbital angular momentum states of light, coupling between spin and orbital angular momentum allows a faster manipulation of orbital angular momentum states because it depends on manipulating the polarisation state of light, which is simpler and generally faster than manipulating conventional orbital angular momentum generators. In this work, we design and fabricate an ultra-thin spin-to-orbital angular momentum converter, based on plasmonic nano-antennas and operating in the visible wavelength range that is capable of converting spin to an arbitrary value of orbital angular momentum l. The nano-antennas are arranged in an array with a well-defined geometry in the transverse plane of the beam, possessing a specific integer or half-integer topological charge q. When a circularly polarised light beam traverses this metasurface, the output beam polarisation switches handedness and the orbital angular momentum changes in value by l = +/- 2q (h) over bar per photon. We experimentally demonstrate l values ranging from +/- 1 to +/- 25 with conversion efficiencies of 8.6% +/- 60.4%. Our ultra-thin devices are integratable and thus suitable for applications in quantum communications, quantum computations, and nanoscale sensing. (C) 2014 AIP Publishing LLC.