Fluorescence microscopy with optical sectioning capabilities is extensively utilized in biological research to obtain three-dimensional structural images of volumetric samples. Tunable lenses have been applied in microscopy for axial scanning to acquire multiplane images. However, images acquired by conventional tunable lenses suffer from spherical aberration and distortions. Here, we design, fabricate, and implement a dielectric Moiré metalens for fluorescence imaging. The Moiré metalens consists of two complementary phase metasurfaces, with variable focal length, ranging from ∼10 to ∼125 mm at 532 nm by tuning mutual angles. In addition, a telecentric configuration using the Moiré metalens is designed for high-contrast multiplane fluorescence imaging. The performance of our system is evaluated by optically sectioned images obtained from HiLo illumination of fluorescently labeled beads, as well as ex vivo mice intestine tissue samples. The compact design of the varifocal metalens may find important applications in fluorescence microscopy and endoscopy for clinical purposes.

The lateral spatial resolution (LSR) in two-photon induced polymerization was improved to 80nm by using an anthracene derivative (9,10-bis-pentyloxy-2,7-bis[2-(4-dimethylamino-phenyl)-vinyl]anthracene (BPDPA)) as a highly sensitive and efficient photoinitiator. Photocurable resin containing 0.18mol% BPDPA exhibited a low polymerization threshold of 0.64mW at 800nm. Theoretical calculations showed that the LSR can be increased by reducing the laser power, indicating that the LSR could be improved using more sensitive initiators in the future.

Negative magnetic permeability of single split-ring resonators (SSRRs) is theoretically investigated in the visible light region. To describe the conduction characteristics of metal in the visible range, we develop the internal impedance formula completely. In our calculations, we determine the magnetic responses of the SSRR accurately. Based on our investigations, we also demonstrate the negative $\mu$ of the silver SSRR array in the visible light region.