Dynamically tunable varifocal device of an abruptly autofocusing beam via a liquid crystal moiré plate

In this work, we propose a moiré-type phase plate utilizing a liquid crystal (LC) element to generate tunable abruptly autofocusing Airy beams (AABs). Based on the cubic phase characteristics of the AAB and the phase modulation principle of the Pancharatnam-Berry phase element, we designed and fabricated an LC-based moiré element capable of adjusting the focal length through element rotation. We theoretically established the relationship between the AABs' focal length and the rotation angle and experimentally generated the AABs with tunable focal lengths. The relative error between the experimentally measured focal lengths and the theoretical prediction remains below 5%. This design holds significant potential for applications in biomedicine and optical micromanipulation.