DIffractive Microlenses With binary focal points on the optical axis

The aim of our study was to find a simple design for diffractive microlenses (DMLs) which will generate two focal points on the propagation axis at plane wave incidence. We investigate the influence of the missing central zones in the diffraction pattern. The fabrication steps include e-beam lithography (for mask pattern) and reactive ion etching (for transparent DMLs). To visualize their transparent binary microrelief and the phase profile, we employ the digital holographic microscopy technique. Experimental and simulation results are presented.