Plasmonic Multibowtie Aperture Antenna with Fano Resonance for Nanoscale Spectral Sorting

In this work we report a new type of nanostructure, the plasmonic multibowtie aperture antenna with Fano resonance for spectral sorting at the nanoscale. Redistribution of surface current in our device plays a critical role in mode coupling to generate Fano resonance, which has never been carefully discussed before. Numerical analyses show that interactions of the electric field, the surface current, and the resulting magnetic field are all important for achieving the desired spectral sorting. Depending on the constructive or destructive interference between the broadband dipole mode and the narrow band multipole mode, electric near-field amplitude and phase distributions switch dramatically across the Fano resonance, which are observed in real space using transmission-type s-SNOM. Based on the Fano interference, photons ranging from visible to infrared spectrum can be sorted through different channels at the nanoscale according to their wavelengths, which shows apparent advantages over other existing nanoscale spectral sorters. Moreover, the narrow gap plasmonic bowtie aperture provides enhanced field of the sorted photons, thus, offers a new approach for multicolor photodetection, optical filtering, and advanced biosensing

Bridged Bowtie Aperture Antenna for Producing an Electromagnetic Hot Spot

In this work we report a new type of nanostructure, the bridged bowtie aperture (BBA) antenna, for producing a simultaneously enhanced and confined electric and magnetic near field. The optical nanocircuit theory is employed to reveal its underlying mechanism. The electric near-field distribution of the nanostructure is observed using transmission-type s-SNOM at the nanoscale, and the magnetic near-field distribution is then derived from the electric near field of a complementary BBA structure using Babinet’s principle. To our knowledge, the generation of such an electromagnetic hot spot has never been experimentally demonstrated. Relative to the existing nanostructures that can produce an electromagnetic hot spot, the BBA antenna has apparent advantages, which offers a new approach for nonlinear optics, surface-enhanced spectroscopy, biosensing, and metamaterials

Visualization 1: Two-stage optical recording: photoinduced birefringence and surface-mediated bits storage in bisazo-containing copolymers towards ultrahigh data memory

Readout of multi-level bits by changing the reading beam polarization. The bits intensities smoothly transit from one state (bright or dack) to the other (dack or bright). Originally published in Optics Express on 03 October 2016 (oe-24-20-23557

Capillary Force Driven Self-Assembly of Anisotropic Hierarchical Structures Prepared by Femtosecond Laser 3D Printing and Their Applications in Crystallizing Microparticles

The hierarchical structures are the derivation of various functionalities in the natural world and have inspired broad practical applications in chemical systhesis and biological manipulation. However, traditional top-down fabrication approaches suffered from low complexity. We propose a laser printing capillary-assisted self-assembly (LPCS) strategy for fabricating regular periodic structures. Microscale pillars are first produced by the localized femtosecond laser polymerization and are subsequently self-assembled into periodic hierarchical architectures with the assistance of controlled capillary force. Moreover, based on anisotropic assemblies of micropillars, the LPCS method is further developed for the preparation of more complicated and advanced functional microstructures. Pillars cross section, height, and spatial arrangement can be tuned to guide capillary force, and diverse assemblies with different configurations are thus achieved. Finally, we developed a strategy for growing micro/nanoparticles in designed spatial locations through solution-evaporation self-assembly induced by morphology. Due to the high flexibility of LPCS method, the special arrangements, sizes, and distribution density of the micro/nanoparticles can be controlled readily. Our method will be employed not only to fabricate anisotropic hierarchical structures but also to design and manufacture organic/inorganic microparticles

Large-Area One-Step Assembly of Three-Dimensional Porous Metal Micro/Nanocages by Ethanol-Assisted Femtosecond Laser Irradiation for Enhanced Antireflection and Hydrophobicity

The capability to realize 2D–3D controllable metallic micro/nanostructures is of key importance for various fields such as plasmonics, electronics, bioscience, and chemistry due to unique properties such as electromagnetic field enhancement, catalysis, photoemission, and conductivity. However, most of the present techniques are limited to low-dimension (1D–2D), small area, or single function. Here we report the assembly of self-organized three-dimensional (3D) porous metal micro/nanocages arrays on nickel surface by ethanol-assisted femtosecond laser irradiation. The underlying formation mechanism was investigated by a series of femtosecond laser irradiation under exposure time from 5 to 30 ms. We also demonstrate the ability to control the size of micro/nanocage arrays from 0.8 to 2 μm by different laser pulse energy. This method features rapidness (∼10 min), simplicity (one-step process), and ease of large-area (4 cm² or more) fabrication. The 3D cagelike micro/nanostructures exhibit not only improved antireflection from 80% to 7% but also enhanced hydrophobicity from 98.5° to 142° without surface modification. This simple technique for 3D large-area controllable metal microstructures will find great potential applications in optoelectronics, physics, and chemistry

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Blood cells bypassing the high-capture sorter

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The high-capture sorting of 5 um particles

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Cancer cells sorting inside the sorter

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Fluorescence microscopy video of cancer cells sorting by the sorter

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The band-capture sorting of 5 um particles