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.