Generation and control of dynamically tunable circular Pearcey beams with annular spiral-zone phase

Light-field shaping technology plays an important role in optics and nanophotonics. For instance, the spatially structured light field, which exhibits characteristic features in complex phases, light intensity, and polarization, is crucial to understanding new physical phenomena and exploring practical applications. Herein, we propose and demonstrate a new class of tunable circular Pearcey beams(TCPBs) by imposing the annular spiral-zone phase(ASZP). Through experiments, we used a spatial light modulator to generate TCPBs based on their spiral phase distribution, and numerically analyzed the generation and control of the beams with unusual autofocusing and self-rotating dynamics. ASZP is a general term for complex phases composed of the spiral phase,equiphase, and radial phase. TCPB typically exhibits dynamical properties, including abrupt autofocusing, automatic generation of optical bottles, and self-rotation of the beam pattern, during propagation. Besides, the number of generated optical bottles can be modulated by the superposition mode of ASZP and the number of subphases. We found that an inappropriate superposition mode leads to distortion, and we analyzed the underlying mechanism. Potential applications of TCPBs in optical manipulation are also discussed, presenting an exemplary role desired for light-field manipulation.

Dual non-diffractive terahertz beam generators based on all-dielectric metasurface

The applications of terahertz(THz)technology can be greatly extended using non-diffractive beams with unique field distributions and non-diffiactive transmission characteristics.Here,we design and experimentally demonstrate a set of dual non-diffractive THz beam generators based on an all-dielectric metasurface.Two kinds of non-diffractive beams with dramatically opposite focusing properties,Bessel beam and abruptly autofocus-ing(AAF)beam,are considered.A Bessel beam with longdistance non-diffractive characteristics and an AAF beam with low energy during transmission and abruptly increased energy near the focus are generated for x-and^-polarized incident waves,respectively.These two kinds of beams are characterized and the results agree well with simulations.In addition,we show numerically that these two kinds of beams can also carry orbital angular momentum by further imposing proper angular phases in the design.We believe that these metasurface-based beam generators have great potential use in THz imaging,communications,non-destructive evaluation,and many other fields.