Subwavelength beam manipulation via multiple-metal slits coupled by disk-shaped nanocavity

A novel plasmonic structure consisting of three nano-scaled slits coupled by nano-disk-shaped nanocavities is pro- posed to produce subwavelength focusing and beam bending at optical frequencies. The incident light passes through the metal slits in the form of surface plasmon polaritons （SPPs） ,and then scatters into radiation fields. Numerical simulations using finite-difference time-domain （FDTD） method show that the transmitted fields through the design example can gener- ate light focusing and deflection by altering the refractive index of the coupled nanocavity. The simulation results indicate that the focal spot is beyond the diffraction limit. Light impinges on the surface at an angle to the optical axis will add an extra planar phase front that interferes with the asymmetric phase front of the plasmonic lens, leading to a larger bending angle off the axial direction. The advantages of the proposed plasmonic lens are smaller device size and ease of fabrication. Such geometries offer the potential to be controlled by using nano-positior!i0g systems for applications in dynamic beam shaping and scanning on the nanoscale.

Broadband acoustic focusing by symmetric Airy beams with phased arrays comprised of different numbers of cavity structures

We realize broadband acoustic focusing effect by employing two symmetric Airy beams generated from phased arrays,in which the units of the phased arrays consist of different numbers of cavity structures, each of which is composed of a square cavity and two inclined channels in air. The exotic phenomenon arises from the energy overlapping of the two symmetric Airy beams. Besides, we demonstrate the focusing performance with high self-healing property, and discuss the effects of structure parameters on focusing performance, and present the characteristics of the cavity structure with straight channels. Compared with other acoustic lenses, the proposed acoustic lens has advantages of broad bandwidth（about 1.4 kHz）, high self-healing property of focusing performance, and free adjustment of focal length. Our finding should have great potential applications in ultrasound imaging and medical diagnosis.

Combination of multiple tools for surface manipulation of polar molecules

A scheme of surface manipulation and control of polar molecules is proposed, which combines three tools of electrostatic velocity filtering, bunching, and storing. In the scheme, a slow molecular beam is produced from an effusive beam by surface velocity filtering. Then the velocity spread of the slow molecular beam is compressed by a buncher consisting of a series of electrodes. Following that the molecular beam with a narrow velocity spread is stored in a storage ring. Using ND3 molecule as a tester, the feasibility of our scheme is analyzed theoretically and verified via numerical simulations that cover all three manipulation processes. The results show that cold molecular samples can be prepared from a thermal gas reservoir and stored in the storage ring with more than 10 round trips. Our combined scheme facilitates the production and manipulation of polar molecules, offering new opportunities for basic research and intriguing applications such as quantum information science and cold collisions.

In-fiber integrated optics： an emerging photonics integration technology [Invited]

In-fiber integrated optics is an attempt to use silica fiber as a substrate, integrating various optical paths or optical components into a single fiber, to build a functional optical device or component, and to realize a micro optical system, achieving various functions. In-fiber integrated optics is expected to he a new branch of photonics integration. This integration technique enables convenient light beams control and manipulation inside in one fiber. It also provides a research platform with micro and nano scale for interaction between light wave and microfluidic materials. In this review, we briefly summarize the main ideas and key technologies of the in-fiber integrated optics by series integration examples.