Dielectric microspheres exhibit the ability to focus an incident beam to a subwavelength spot with strong localized field intensity. In this Letter, a high beam quality of a longitudinally polarized electromagnetic component is created by decorating the surface of the microsphere with engineered structures. By changing the design of the engineered microspheres, the relative contribution of the longitudinal and radial components of a radially polarized incident beam to the photonic nanojet can be modified efficiently, leading to a sharp spot size which exceeds the optical diffraction limit. More importantly, a high conversion efficiency of 0.89 is achieved. At a wavelength of 633 nm, a focal spot of 266 nm (0.42λ) is achieved numerically by illuminating the engineered microsphere with a focusing beam at a numerical aperture of 0.7.

Processing of mesoscale structures of soft matter and liquid is of great importance in both science and engineering. In this work, we introduce the concept of laser-assisted micromachining to this field and inject a certain number of microdroplets into a preselected location on the surface of a liquid crystal drop through laser irradiation. The impact of laser energy on the triggered injection is discussed. The sequentially injected microdroplets are spontaneously captured by the defect ring in the host drop and transported along this defect track as micro-cargos. By precisely manipulating the laser beam, the tailored injection of droplets is achieved, and the injected droplets self-assemble into one necklace ring within the host drop. The result provides a bottom-up approach for the in-situ and three-dimensional microfabrication of droplet structure of soft matter using a laser beam, which may be applicable in the development of optical and photonic devices.

No abstract

No abstract

To control the spatial placement and organize micro/nanodroplets (NDs) has fundamental importance both in science and engineering. Cholesteric liquid crystal (CLC) droplets with topological diversity can offer many self-assembly modalities to arrange guest NDs in their spherical confinement; however, limited progress has been achieved due to difficulties of loading NDs into stabilized host droplets. Here, a laser injection technique is introduced, through which a controlled number of NDs were injected from a pre-selected location onto the surface of the host droplet. The sequentially injected NDs spontaneously drifted toward areas with topological defects and self-assembled along its geometry or local director field into a predefined shape. Within CLC droplets with different topological structures, guest NDs self-assembled near areas with defect points as twisting radial chains and quill-like assembly structures, and along defect lines as discrete beads and helical threads, respectively. The injection speed of the NDs, controlled by laser power, was found to play a key role in the assembly geometry of NDs as well as the internal structure of the CLC droplet processed. This study expands our abilities to precisely organize NDs in a spherical confinement and such droplet-based microsystems have potential applications for sensors, photonic devices, pharmaceuticals, and biotechnology.