Steering abrupt autofocusing beams with metasurfaces [Invited]

Abrupt autofocusing (AAF) beams, known for their non-diffractive properties, extended focal depth, and self-healing capabilities, are advantageous over conventional Gaussian beams in the biomedical field. Compared to the previous method that can only generate a passive AAF beam, we introduce metasurfaces to achieve a dynamically steered AAF beam at the incident wavelength of 532 nm. By rotating the two metasurfaces in opposite directions of an angle θ , both the generated position of the AAF beam and the autofocusing direction can be altered. Our theoretical analysis and full-wave simulation results confirmed that the deflection angle of the AAF beam can be finely adjusted from to 11° without significantly affecting the focal length or focusing efficiency. This capability allows for precision operation in biomedical applications, including enhanced laser surgery, optical tweezing, and optimized photodynamic therapy.