All-Dielectric Synthetic-Phase Metasurfaces Generating Practical Airy Beams.

ABSTRACT

Accelerating optical beams exhibit exotic features, such as nondiffractive propagation, self-acceleration, and self-healing, which have led their use in a wide range of photonics applications. However, spatial light modulator-based generators of such beams suffer from narrow operational bandwidth, high cost, low diffraction efficiency, and limited integration capability. Although recent metasurface-based approaches have yielded generators with significantly improved bandwidths and integration capacities, the resultant devices usually have ultrashort working distances and limited control over characteristic beam parameters, which decreases their utility in optical imaging and manipulation applications. Herein, we describe a synthetic-phase metasurface-based approach that overcomes these problems and increases the degrees of freedom to enable effective control of beam parameters by integrating a cubic phase profile and the phase of a Fresnel holographic lens into a single metasurface. We demonstrate this approach by using the synthetic metasurface to generate a series of Airy beams with controllable focal length (i.e., working distance), narrowed beam width, and extended propagation distance. Crucially, these beam parameters are fully adjustable, which makes these focal-length-modifiable Airy beams particularly appealing for use in high-resolution, large field-of-view imaging, and deep-penetration optical manipulation. Furthermore, we show that imposing the phase of a Dammann grating into a synthetic metasurface generates a 1 × 4 array of Airy beams that exhibit the aforementioned optical properties. These findings suggest that synthetic-phase metasurfaces may significantly broaden the application of accelerating optical beams in various fields, such as light-sheet microscopy, super-resolution stochastic optical-reconstruction microscopy, laser fabrication, and parallel processing and in the development of optical tweezers for use with live samples.