The precise control and manipulation of micro- and nanoparticles using an optical endoscope are potentially important in biomedical studies, bedside diagnosis and treatment in an aquatic internal organ environment, but they have not yet been achieved. Here, for the first time, we demonstrate optical nonlinear endoscopic tweezers (ONETs) for directly controlling and manipulating aquatic micro- and nanobeads as well as gold nanorods. It is found that two-photon absorption can enhance the trapping force on fluorescent nanobeads by up to four orders of magnitude compared with dielectric nanobeads of the same size. More importantly, two-photon excitation leads to a plasmon-mediated optothermal attracting force on nanorods, which can extend far beyond the focal spot. This new phenomenon facilitates a snowball effect that allows the fast uploading of nanorods to a targeted cell followed by thermal treatment within 1 min. As two-photon absorption allows an operation wavelength at the center of the transmission window of human tissue, our work demonstrates that ONET is potentially an unprecedented tool for precisely specifying the location and dosage of drug particles and for rapidly uploading metallic nanoparticles to individual cancer cells for treatment.

Radiative heat transfer between two polar nanostructures at different temperatures can be enhanced by resonant tunneling of surface polaritons. Here we show that the heat transfer between two nanoparticles is strongly varied by the interactions with a third nanoparticle. By controlling the size of the third particle, the time scale of thermalization toward the thermal bath temperature can be modified over 5 orders of magnitude. This effect provides control of temperature distribution in nanoparticle aggregation and facilitates thermal management at nanoscale.

We demonstrate a three dimensional nanoparticle trapping approach aided by the surface plasmon resonance of metallic nanostructures. The localized surface plasmon resonance effect provides strong electromagnetic field enhancement, which enables confinement of nanoparticles in the three-dimensional space. Numerical simulations indicate that the plasmonic structure provides approximately two orders of magnitude stronger optical forces for trapping nanoparticles, compared with that without nanostructures. The study of thermal effect of the plasmonic structure shows that the impact of the thermal force is significant, which may determine the outcome of the nanoparticle trapping.

The issues of security and obstruction of line of sight are concerns of wireless optical communications (WOC). In this paper, an analysis of light beams carrying orbital angular momentum (OAM) used for WOC is undertaken. The basic description and conception of OAM of light are given. Encoding information both as the OAM states of a single light beam and as the spatial structure of the mixed light beams with OAM is discussed and compared. Using OAM to encode the data offers an inherent security enhancement. Mixed vortex fields with OAM possess a self-reconstruction property that is able to regenerate and to reconstruct their initial spatial distributions of the complex amplitude in the condition of obstruction of line of sight.

Periodic nanostructures consisting of metal-dielectric nanostructures array are studied for refractive index (RI) sensing. The anapole mode of metal-dielectric structure is used to enhance plasmonic resonance and reduce energy losses. High sensitivity RI sensing can be achieved by the nanostructure with circular polarization illumination. Numerical results show that the sensor exhibit almost perfect linearity of resonance wavelength shift with RI ranging from 1.3 to 1.39 with sensitivity of 593 nm RIU ⁻¹ . The proposed nanostructure could find applications in biomolecules manipulation and optical sensors.