Tunable abrupt autofocusing meta-devices

Abrupt autofocusing (AAF) beams [1], integrating features of circular Airy and Bessel beams, offer extended focal depths, self-healing properties, high precision, and minimal energy loss. These qualities make them ideal for advanced optical imaging, particle trapping, and laser surgery. Traditionally, spatial light modulators (SLMs) have been used to generate AAF beams by encoding their Fourier transform. However, SLMs suffer from low resolution, energy inefficiency, and a limited operational wavelength range, which hinder precise nanoscale operations. Additionally, their bulky size is at odds with the trend towards device miniaturization and integration. Metasurfaces [2-4], capable of manipulating wavefronts at subwavelength scales, present a superior alternative to traditional optical devices by offering reduced weight, increased efficiency, smaller size, and lower energy consumption. Metasurfaces have found applications [5-7] in beam shaping, achromatic imaging, light-field sensing, holography, optical computing, quantum technologies, and biological imaging. Yet, challenges remain in biomedical applications, particularly in creating dynamic beams essential for improving image contrast, optical tweezing, and optimizing photodynamic therapy. © 2024 Japan Society of Applied Physics.