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.