| Summary: | We present a simple and highly efficient approach to directly generate tunable Airy beams, which can propagate along arbitrary monotonic curves. Such beams are generated by modulating a Gaussian beam imposed by tunable phase-only patterns. The analytic relationship between phase and propagation trajectory is derived by applying caustic theory. In addition, by utilizing symmetry of phase, we also generate tunable quadrate Airy beams that are composed of four independent Airy beams. As opposed to conventional Airy beams, quadrate Airy beams exhibit distinctly symmetric intensity profiles, autofocusing, and tunable trajectories. Moreover, such beams present a thin needle-like structure in the focus region along longitudinal directions. Despite differences in propagation trajectories, such accelerating beams also show nondiffracting and self-healing characteristics. Experimental results agreed well with theoretical predictions. The tunability of such beams may provide further possibilities for applications such as flexible optical manipulation. (The caption of Graphic Abstract is geometrical model of the tunable Airy beams).
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