Fractal Holey Metal Microlenses with Significantly Suppressed Side Lobes and High-Order Diffractions in Focusing

A fractal holey metal microlens based on finite areas of two-dimensional arrays of circular nanoholes is reported. Both experimental and simulation results confirm that the fractal holey metal microlens can significantly suppress both the side lobes and high-order diffractions. The ultra-thin, planar, and compact design of the fractal holey metal microlenses with excellent focusing performance will benefit many applications such as bioimaging, optical trapping, and integrated optics.