A new publication in Opto-Electronic Advances, 10.29026/oea.2024.230171, describes a miniature tunable Airy beam optical metadevice.
Airy beams have attracted wide research interest due to their unique properties such as non-diffracting, self-acceleration, and self-healing. Since its discovery, the growing demand for tunable Airy beams has led to systematic research into optical manipulation and laser processing. Optical trapping is typically achieved by generating optical gradient forces with tightly focused Gaussian beams. This force is primarily exploited to confine particles within a few micrometers due to the relatively short Rayleigh length. In contrast, Airy beams have the ability to optically manipulate particles in air or liquid along specified paths and through obstacles by precisely controlling their propagation trajectories. These beams can also facilitate the processing of surfaces with desired curvature to increase the flexibility of laser manufacturing.
Methods to generate Airy beams typically require complex and expensive optical devices, such as complex optical lens systems and spatial light modulators (SLMs). These technologies provide a pathway to achieve adjustable Airy beams. Complex optical lens systems can produce tunable Airy beams by adjusting the tilt angle of the cylindrical lens system. The SLM achieves a tunable Airy beam by performing pixel-level phase changes. Although these methods have the advantage of providing some control over the Airy beam, each technique has its own drawbacks. Complex optical setups inevitably create difficulties in achieving precise alignment. SLMs face problems such as low conversion efficiency, limited resolution, input polarization, and power constraints. These technologies also struggle to achieve compact, integrated optical systems due to the use of bulky components.
Currently, there are several studies focusing on the generation of Airy beams using metasurfaces. For example, by combining cubic phase and different lens profiles, different Airy beams with diverse trajectories can be generated. Additionally, integrating the cubic and gradient phases into a single metasurface allows precise control of the Airy beam’s trajectory. Even though current research has demonstrated various methods for manipulating the propagation trajectory and focal position of Airy beams within a confined space, it is still difficult to adjust the generated Airy beams in real time. It Is difficult.
The authors of this article propose a new approach to generate tunable Airy beams utilizing a bilayer all-dielectric metadevice. The method involves the integration and rotation of carefully designed phase profiles, including a cube and two off-axis Fresnel lens phase profiles. Tunability of Airy beam generation is achieved by dynamically manipulating the Airy beam trajectory through the rotation of these two metasurfaces, as shown in Figure 1. We conduct an experimental investigation of a proof-of-concept metadevice to verify its feasibility and flexibility. These experimental results are in good agreement with the theoretically predicted Airy beam intensity profile and propagation dynamics.
This technique of adjusting the focus and propagation path of an Airy beam can facilitate optical manipulation and laser manufacturing. Airy beam propagation trajectory and coverage manipulation capabilities can be easily customized by adjusting these phase profile parameters. This approach effectively enhances the modulation flexibility of the Airy beam without increasing the device footprint. Real-time rotation of the metasurface enabled by piezoelectricity further enhances the tunability and flexibility of these metadevices. Compared to traditional tilted cylinder telescoping systems or SLMs, the demonstrated metadevice significantly reduces volumetric thickness and operational complexity. This helps better exploit his three characteristics of Airy beams: non-diffracting, self-acceleration, and self-healing. Additionally, it can be seamlessly adapted to other operating bands without being constrained by polarization or other limitations. Leveraging the advantages of miniaturization and easy control, the proposed metadevice is compatible with various optical devices and holds great promise for various applications.
Keywords: Metasurface / Small Device / Tunable Airy Beam / Tunable Metadevice
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