Phys. Rev. Lett. 109, 193901 (2012)

Credit: XIANG ZHANG

Airy beams — accelerating beams that possess non-diffracting and self-healing properties — are subject to a paraxial limit, which means they lose these properties after bending to large angles along their parabolic trajectories. Peng Zhang and colleagues from the USA and Canada have now theoretically and experimentally demonstrated two new classes of accelerating beams that do not suffer from this limitation: non-paraxial Mathieu accelerating beams (MABs) and Weber accelerating beams (WABs). The beams were found as solutions to the Helmholtz equation in elliptical and parabolic coordinate systems, respectively, without the need for a paraxial approximation. The researchers showed that a circular non-paraxial accelerating beam is a special case of an elliptical MAB, and that the Airy beam is a paraxial approximation of a WAB. They experimentally realized the beams by sending a 532 nm laser through a holographic mask whose phase and intensity information were reconfigurable. The findings not only generalize the concept of accelerating beams, but also offer larger degrees of freedom in beam engineering for practical applications, such as microparticle manipulation and surface plasmon routing.