Yang Qingshuai, Xie Zijian, Zhang Mengrui, Ouyang Xu, Xu Yi, Cao Yaoyu, Wang Sicong, Zhu Linwei, Li Xiangping
Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou, 510632, China.
Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou, 510632, China.
Nanophotonics. 2022 Jan 31;11(5):1063-1070. doi: 10.1515/nanoph-2021-0786. eCollection 2022 Feb.
Light's orbital angular momentum (OAM) with inherent mode orthogonality has been suggested as a new way to the optical encryption. However, the dependence of annular intensity profiles on the topological charge complicates nanoscale light-matter interactions and hampers the ultra-secure encryption application. In this paper, we demonstrate ultra-secure image encryption by tightly focusing perfect optical vortex (POV) beams with controllable annular intensity profiles and OAM states. A simple scheme composed of single spatial light modulator to implement Fourier transform of an ideal Bessel mode with both amplitude and phase modulations is proposed to generate radius-controllable POV in tightly focused beams. Such focused POV beams with identical intensity profiles but varied local OAM density are applied to disorder-coupled gold nanorod aggregates to selectively excite electromagnetic hot spots for encoding information through photothermal deformation. As such, ultra-secure image encryption in OAM states of POV beams in combination with different polarizations can be achieved. Our results lay the ground for diverse nanophotonic applications harnessing the OAM division of POV beams.
具有固有模式正交性的光的轨道角动量（OAM）已被提议作为一种新的光学加密方法。然而，环形强度分布对拓扑电荷的依赖性使纳米级光与物质的相互作用变得复杂，并阻碍了超安全加密应用。在本文中，我们通过紧密聚焦具有可控环形强度分布和OAM态的完美光学涡旋（POV）光束来演示超安全图像加密。提出了一种由单个空间光调制器组成的简单方案，通过幅度和相位调制来实现理想贝塞尔模式的傅里叶变换，以在紧密聚焦光束中生成半径可控的POV。将具有相同强度分布但局部OAM密度不同的这种聚焦POV光束应用于无序耦合的金纳米棒聚集体，以选择性地激发电磁热点，通过光热变形来编码信息。这样，就可以实现结合不同偏振的POV光束的OAM态的超安全图像加密。我们的结果为利用POV光束的OAM划分的各种纳米光子应用奠定了基础。
