Laser-induced subwavelength structures by microdroplet superlens

Controllable Formation and Real-Time Characterization of Single Microdroplets Using Optical Tweezers

Existing preparation methods for microdroplets usually require offline measurements to characterize single microdroplets. Here, we report an optical method used to facilitate the controllable formation and real-time characterization of single microdroplets. The optical tweezer technique was used to capture and form a microdroplet at the center of the trap. The controllable growth and real-time characterization of the microdroplet was realized, respectively, by adjusting experimental parameters and by resolving the Raman spectra by fitting Mie scattering to the spike positions of the spectra during the controllable growth of microdroplets. The proposed method can be potentially applied in optical microlenses and virus detection.

Enhancement of efficiency on the Pancharatnam-Berry geometric phase metalens in the terahertz region

Traditional terahertz lenses face high thickness, low transmittance, difficult processing, and other problems that are not conducive to mass production and integration. Here, we propose a wideband all-dielectric Pancharatnam-Berry geometric phase cell structure to construct a metasurface flat lens. However, when the geometrical phase element structure rotates, the transmission efficiency of the periodic element structure obviously decreases, which will lead to the decrease of the efficiency of the designed flat lens. In order to improve the efficiency, we propose to add a layer of tapered microstructure on the flat substrate to greatly improve the transmission efficiency of the element structure, thus leading to the improvement of the efficiency of the metasurface lens. By comparing the metasurface lens with conical and planar substrates, the metasurfaces with conical structure can greatly improve the transmission efficiency at broadband and wide angle ranges.