Opt Express. 2021 Feb 1;29(3):3795-3807. doi: 10.1364/OE.416698.
With the novel capabilities of engineering the optical wavefront at the nanoscale, the dielectric metalens has been utilized for fluorescence microscopy imaging system. However, the main technical difficulty is how to realize the achromatic focusing and light modulation simultaneously by a single-layer metalens in the two-photon excitation STED (TPE-STED) endomicroscopy imaging system. Herein, by combining the spatial multiplexing technology and vortex phase modulation, a single-layer multitasking vortex-metalens as a miniature microscopy objective on the end of fiber was proposed. The multitasking vortex-metalens with 36-sectors interleaving (diameter of 100 μm) could focus the excitation beam (1050 nm) and depletion beam (599 nm) to the same focal distance, modulate a doughnut-shaped depletion spot with vortex phase and reshape the focal spots to further make improvement in the quality and symmetry. According to the TPE-STED theory, a symmetrical effective fluorescent spot with the lateral resolution of 30 nm was obtained by the proposed metalens. Thus, with the advantage of ultra-compact and lightweight, we prospect that the subminiature multitasking metalens will help guide future developments in high-performance metalenses toward high-resolution and real-time images for deep biological tissue in vivo and enable scientific high-end miniature endomicroscopy imaging system.
利用在纳米尺度上工程化光学波前的新能力，介电金属透镜已被用于荧光显微镜成像系统。然而，主要的技术难点是如何通过单层金属透镜在双光子激发 STED（TPE-STED）内窥成像系统中同时实现消色差聚焦和光调制。在此，通过结合空间复用技术和涡旋相位调制，提出了一种作为光纤末端微型显微镜物镜的单层多任务涡旋金属透镜。该多任务涡旋金属透镜由 36 个扇形交错排列（直径为 100μm）组成，可以将激发光束（1050nm）和耗尽光束（599nm）聚焦到相同的焦距处，调制具有涡旋相位的环形耗尽光斑，并重塑焦点，以进一步改善质量和对称性。根据 TPE-STED 理论，通过所提出的金属透镜获得了具有 30nm 横向分辨率的对称有效荧光光斑。因此，凭借超紧凑和轻量级的优势，我们预计这种亚微型多任务金属透镜将有助于引导高性能金属透镜向高分辨率和实时成像的方向发展，用于体内深层生物组织，并实现科学的高端微型内窥成像系统。
