Optical surface waves have widely been used in optical tweezers systems for trapping particles sized from the nano- to microscale, with specific importance and needs in applications of super-resolved detection and imaging if a single particle can be trapped and manipulated accurately. However, it is difficult to achieve such trapping with high precision in conventional optical surface-wave tweezers. Here, we propose and experimentally demonstrate a new method to accurately trap and dynamically manipulate a single particle or a desired number of particles in holographic optical surface-wave tweezers. By tailoring the optical potential wells formed by surface waves, we achieved trapping of the targeted single particle while pushing away all surrounding particles and further dynamically controlling the particle by a holographic tweezers beam. We also prove that different particle samples, including gold particles and biological cells, can be applied in our system. This method can be used for different-type optical surface-wave tweezers, with significant potential applications in single-particle spectroscopy, particle sorting, nano-assembly, and others.

Polarization imaging finds applications in many areas, such as photoelasticity, ellipsometry, and biomedical imaging. A compact, snapshot, and high-efficiency imaging polarimeter is highly desirable for many applications. Here, based on a single multifunctional geometric phase optical element (GPOE), a new method is proposed for high-efficiency snapshot imaging polarimetry. With tailored spatially varying orientation of each anisotropic unit cell, the GPOE works highly efficiently as both a spin sorter and a half-wave plate, enabling snapshot retrieving of a full Stokes vector of incident light. The designed GPOE is implemented in the form of liquid crystal fabricated with a photo-alignment technology, and its application in imaging polarimetry is experimentally demonstrated by retrieving full Stokes parameters of a cylinder vector beam. This method can also work in the form of plasmonic or dielectric metasurfaces, enabling ultra-compact polarization detection systems by monolithic integration with other devices such as metalenses.

Strong plasmonic focal spots, excited by radially polarized light on a smooth thin metallic film, have been widely applied to trap various micro- and nano-sized objects. However, the direct transmission part of the incident light leads to the scattering force exerted on trapped particles, which seriously affects the stability of the plasmonic trap. Here we employ a novel perfect radially polarized beam to solve this problem. Both theoretical and experimental results verify that such a beam could strongly suppress the directly transmitted light to reduce the piconewton scattering force, and an enhanced plasmonic trapping stiffness that is 2.6 times higher is achieved in experiments. The present work opens up new opportunities for a variety of research requiring the stable manipulations of particles.

Optical traps use focused laser beams to generate forces on targeted objects ranging in size from nanometers to micrometers. However, for their high coefficients of scattering and absorption, micrometer-sized metallic particles were deemed non-trappable in three dimensions using a single beam. This barrier is now removed. We demonstrate, both in theory and experiment, three-dimensional (3D) dynamic all-optical manipulations of micrometer-sized gold particles under high focusing conditions. The force of gravity is found to balance the positive axial optical force exerted on particles in an inverted optical tweezers system to form two trapping positions along the vertical direction. Both theoretical and experimental results confirm that stable 3D manipulations are achievable for these particles regardless of beam polarization and wavelength. The present work opens up new opportunities for a variety of in-depth research requiring metallic particles.