Two-step microfocal lens with enhanced optical coupling efficiency suitable for large-scale fabrication

A two-step microfocal lens design that can achieve high-efficiency optical coupling is reported. Simulation results show that the lens enhances optical coupling efficiency by over one-third compared with its prototype previously reported. It also slightly reduces the focal spot size. A simple top-down fabrication process flow is discussed, which indicates that the proposed two-step lens can be fabricated at low cost using conventional industrial equipment.