A Simple Way to Fabricate Close-Packed High Numerical Aperture Microlens Arrays

We present a developed femtosecond laser enhanced wet chemical etching method to fabricate close-packed and high numerical aperture (NA) microlens arrays (MLAs). Its ability to fabricate 100% fill factor MLAs with controllable NA is demonstrated and the maximum NA value of the lenses reaches to 0.47. This letter provides a simple and efficient way to achieve controllable and low cost optical elements. The close-packed and high-NA properties lead to excellent optical performance of the MLAs, which are highly required in high-resolution and high-signal-to-noise-ratio detections in micro-optical and integrated optical applications.

I. Introduction

Microlenses and microlens arrays (MLAs) with diameters of a few to hundreds micrometers are widely used in micro-manufacturing, display and image sensing due to the enhancement light collimation and collection efficiency [1]–[4]. Fill factor and numerical aperture (NA) are two critical parameters that influence the optical performance of the MLAs. High-fill-factor MLAs will capture most incident lights to increase the signal-noise-ratio, and high-NA microlenses can generate high-resolution images. These characteristics are highly required in optical interconnects, bio-detection system, laser protection goggle, 2D optical data recording and projection systems [4], [5]. Close-packed high numerical aperture microlens arrays are continuously pursued.