Zhao Maoxiong, Chen Mu Ku, Zhuang Ze-Peng, Zhang Yiwen, Chen Ang, Chen Qinmiao, Liu Wenzhe, Wang Jiajun, Chen Ze-Ming, Wang Bo, Liu Xiaohan, Yin Haiwei, Xiao Shumin, Shi Lei, Dong Jian-Wen, Zi Jian, Tsai Din Ping
State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education) and Department of Physics, Fudan University, 200433, Shanghai, China.
Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, 999077, Hong Kong, China.
Light Sci Appl. 2021 Mar 10;10(1):52. doi: 10.1038/s41377-021-00492-y.
Metalenses have emerged as a new optical element or system in recent years, showing superior performance and abundant applications. However, the phase distribution of a metalens has not been measured directly up to now, hindering further quantitative evaluation of its performance. We have developed an interferometric imaging phase measurement system to measure the phase distribution of a metalens by taking only one photo of the interference pattern. Based on the measured phase distribution, we analyse the negative chromatic aberration effect of monochromatic metalenses and propose a feature size of metalenses. Different sensitivities of the phase response to wavelength between the Pancharatnam-Berry phase-based metalens and propagation phase-reliant metalens are directly observed in the experiment. Furthermore, through phase distribution analysis, it is found that the distance between the measured metalens and the brightest spot of focusing will deviate from the focal length when the metalens has a low nominal numerical aperture, even though the metalens is ideal without any fabrication error. We also use the measured phase distribution to quantitatively characterise the imaging performance of the metalens. Our phase measurement system will help not only designers optimise the designs of metalenses but also fabricants distinguish defects to improve the fabrication process, which will pave the way for metalenses in industrial applications.
近年来，超颖透镜已成为一种新型光学元件或系统，展现出卓越的性能和丰富的应用。然而，迄今为止超颖透镜的相位分布尚未得到直接测量，这阻碍了对其性能进行进一步的定量评估。我们开发了一种干涉成像相位测量系统，通过仅拍摄一张干涉图样照片来测量超颖透镜的相位分布。基于所测量的相位分布，我们分析了单色超颖透镜的负色差效应，并提出了超颖透镜的特征尺寸。在实验中直接观察到了基于潘查拉特纳姆 - 贝里相位的超颖透镜和基于传播相位的超颖透镜之间相位响应随波长的不同灵敏度。此外，通过相位分布分析发现，当超颖透镜的标称数值孔径较低时，即使超颖透镜是理想的且没有任何制造误差，所测量的超颖透镜与聚焦最亮点之间的距离也会偏离焦距。我们还利用所测量的相位分布来定量表征超颖透镜的成像性能。我们的相位测量系统不仅将有助于设计人员优化超颖透镜的设计，还将帮助制造人员识别缺陷以改进制造工艺，这将为超颖透镜在工业应用中铺平道路。
