高效产生艾里光束的偏振无关介电质超表面

艾里光束因其具有自加速、自愈合和近乎无衍射的优异特性,引起了人们极大的研究兴趣。目前,已有多种方案来生成艾里光束。其中,空间光调制器因其具有较大的液晶单位尺寸,使得该方法降低了特定艾里光束的质量,并具有光路不紧凑、成本高等缺点。

用于产生艾里光束的表面等离子体或介电质超表面虽然具有亚波长像素尺寸的相位分布、部件易于集成和低成本的优点,但同步调控振幅和相位的方法限制了艾里光束的生成效率。此外,目前多数实验中已经实现的用于生成艾里光束的超表面是偏振敏感的。然而,进一步扩展艾里光束的应用需要有两点重要的特性,即高的产生效率和偏振无关特性。

上海理工大学庄松林院士、顾敏院士领导的“未来光学”实验室的张大伟教授、文静副教授课题组提出了利用偏振无关的介电质超表面高效率产生艾里光束的方法。张大伟教授、文静副教授为通讯作者,余彬彬博士生为第一作者,合作作者还包括香港城市大学的雷党愿副教授课题组。该成果发表在Photonics Research 2020年第7期上(Binbin Yu, Jing Wen, Lei Chen, et al. Polarization-independent highly efficient generation of Airy optical beams with dielectric metasurfaces[J]. Photonics Research, 2020, 8(7): 07001148)。

在这项研究中,研究人员采用了3/2纯相位调控代替了同步控制振幅和相位的方法。该方案具有以下优势:首先,在纳米圆柱单元的直径覆盖该参数值范围三分之二的情况下,纳米圆柱的光场透过率都能保持接近100%;其次,生成的艾里光束不需要考虑输入光束的偏振态,输出光束不需要过滤;最后,该方法实现了主瓣半高全宽小、弯曲系数高的艾里光束的生成。

本文研究团队认为,这一方案将为艾里光束在红外传感、大气光学、荧光成像以及激光制造等领域的应用发挥重要作用。未来的研究将会集中在对艾里光束内在特性参数进行定量的调控,以使艾里光束能够更方便应用在各种不同的和某种特定的场景。

高效产生艾里光束的偏振无关介电质超表面

Polarization-independent highly efficient generation of Airy optical beams with dielectric metasurfaces

Airy optical beams have come out to stir up enormous research interests due to their extraordinary characteristics of self-accelerating, self-healing, and being nearly diffraction free. There are various schemes to generate Airy beams, for instance, using spatial light modulators (SLMs). However, they significantly condense the quality of the generated Airy beams due to the poor phase discretization, as Airy beams possessing specific characteristics need phase profiles with large phase slope. Although lately several plasmonic or dielectric metasurface-based generators provide phase profiles with subwavelength pixelization offering a compact and cost-effective platform, the method based on synchronous manipulation of the amplitude and phase limits the generation efficiency of Airy beams. Besides, most of currently demonstrated metasurface-based Airy beam generators are polarization-sensitive.

To circumvent the above limitations, Prof. Dawei Zhang's group from Engineering Research Center of Optical Instrument and Systems and Ministry of Education and Shanghai Key Laboratory of Modern Optical System, affiliated to "Future Optics" Laboratory lead by Academician Songlin Zhuang and Academician Min Gu, University of Shanghai for Science and Technology, China, has proposed and experimentally demonstrated polarization-independent highly efficient generation of Airy optical beams with dielectric metasurfaces. The corresponding result is published in Photonics Research, Vol. 8, Issue 7, 2020 (Binbin Yu, Jing Wen, Lei Chen, et al. Polarization-independent highly efficient generation of Airy optical beams with dielectric metasurfaces[J]. Photonics Research, 2020, 8(7): 07001148).

This study implements a scheme based on the 3/2 phase-only manipulation by spatially varying the diameter of the dielectric cylindrical unit element of the metasurface, instead of synchronous manipulation of the amplitude and phase. As a result, this scheme has several advantages in the following aspects. First, the transmission of the nano-pillar element is near-unity as the diameter falls in two-thirds of the whole parameter range. Second, a distinct envelope of the resultant Airy beam is molded right away without filtration of the polarization states for the input and output beams. Third, high average generation efficiency of the demonstrated highly deflected Airy optical beams with trivial beam widths is achieved.

Prof. Dawei Zhang and Asso. Prof. Jing Wen believe the presented scheme will open the door for Airy beams to play a vital role in infrared sensing, atmospheric optics, fluorescence imaging, laser fabrication etc. Future work will focus on quantification and tuning the inherent parameters of Airy beams to explore the beams in potentially various and specific applications.

Caption: Polarization-independent highly efficient generation of Airy optical beams with dielectric metasurfaces