Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Published: May 2012
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Article Abstract
Optical trapping of gold nanoparticles is experimentally demonstrated using radially and azimuthally polarized beams. The transverse optical trapping stiffness of gold nanoparticles is measured. The radially polarized beam exhibits a higher trapping efficiency than the azimuthally polarized beam and the Gaussian beam. The transverse stiffness of particles with different diameters is measured experimentally and calculated via the discrete-dipole approximation method, and good agreement between theory and experiment is found.
In this Letter, we have proposed an all-optical scheme for chiral particle separation with a microcylinder-pair system (MCPS) with a micrometer scale channel, applicable in microfluidic environments. By illuminating the MCPS with two counter-incident plane waves of orthogonal polarization, the electromagnetic chirality gradient can be generated. The MCPS can also enhance chirality-dependent lateral optical forces of the coupled fields so that the setup can shift trapping equilibrium positions for opposite-handedness nanoparticles and make the sideways motion observable.
Light-matter interaction is a long-standing promising topic that can be dated back to a few centuries ago and has witnessed the long-term debate between the particle and wave nature of light. In modern condensed matter physics and materials science, light usually serves as a detection tool to effectively characterize the physical and chemical features of samples. The light modulation on intrinsic properties of materials, such as atomic geometries, electronic bands, and magnetic behaviors, is more intriguing for information control and storage.
Chiral objects are abundant in nature, and although the enantiomers have almost identical physical properties apart from their handedness, they can exhibit significantly different chemical properties and biological functions. This underscores the importance of sorting chiral substances. In this Letter, we demonstrate that chirality-sorting optical force pairs can be inversely generated in a tightly focused Gaussian beam by tailoring the input polarization state.
Center of Single-Molecule Sciences, Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China.
Via conductance measurements of thousands of single-molecule junctions, we report that the π-π coupling between neighboring aromatic molecules can be manipulated by laser illumination. We reveal that this optical manipulation originates from the optical plasmonic gradient force generated inside the nanogaps, in which the gapped antenna electrodes act as optical tweezers pushing the neighboring molecules closer together. These findings offer a nondestructive approach to regulate the interaction of the molecules, deepening the understanding of the mechanism of π-π interaction, and open an avenue to manipulate the relative position of extremely small objects down to the scale of single molecules.
Zinc ferrite (ZnFeO, ZFO) has gained attention as a candidate material for photoelectrochemical water oxidation. However, champion devices have achieved photocurrents far below that predicted by its bandgap energy. Herein, strong optical interference is employed in compact ultrathin film (8-14 nm) Ti-doped ZFO films deposited on specular back reflectors to boost photoanode performance through enhanced light trapping, resulting in a roughly fourfold improvement in absorption as compared to films deposited on transparent substrates.
