Tunable Focal Depth of Amplitude-Modulated Circular Airy Beams

Focal depth tuning provides an effective way to enhance the longitudinal flexibility of circular Airy beams (CABs). In this work, we investigate the control of focal depth in CABs by introducing an adjustable amplitude coefficient and varying the aperture radius. The results show that the focal depth can be flexibly tuned, and the amplitude-modulated CAB achieves a focal intensity nearly an order of magnitude higher than that of a conventional CAB. The propagation dynamics are examined through theoretical analysis, numerical simulations, and experimental measurements. A phase-only spatial light modulator is employed to generate the modulated CAB, and the recorded intensity profiles exhibit good agreement with the theoretical predictions. These findings demonstrate that amplitude-modified CABs offer enhanced longitudinal control and hold great potential for applications such as optical trapping, high-resolution imaging, and precision distance measurement.