Fabrication of Hexagonal Microlens Arrays on Single-Crystal Silicon Using the Tool-Servo Driven Segment Turning Method.

Mao Mukaida,Jiwang Yan

doi:10.3390/mi8110323

Abstract

Single-crystal silicon microlens arrays are increasingly required in advanced infrared optics. In this study, the authors attempted to fabricate hexagonal microlens arrays, which offer high optical efficiency, on a single-crystal silicon wafer using diamond turning. A tool-servo driven segment turning method was proposed to reduce the dynamic error of the machine tool induced by lenslet edges during lens array cutting. From the results of both cutting experiments and theoretical analysis of the machine tool dynamic error, it was demonstrated that the segment turning method reduced significantly the dynamic errors and led to high form accuracy. As a result, sharp edges among the lenslets were generated precisely and microlens arrays with a form error of ~300 nm peak-to-valley and surface roughness of ~5 nmSa, which meets the requirements of infrared optical systems, were successfully fabricated. The subsurface damage, such as the amorphization of silicon, caused by machining was also reduced.

Highlights

In recent years, infrared (IR) optical systems are increasingly demanded in many fields such as security and remote sensing
Spherical and aspherical lenses of single-crystal silicon have been used in IR optical systems so far [1,2,3], the silicon lens with its more complex shapes is in demand for future IR optical systems
Microlens arrays have been widely used in optical systems but currently most of them are made of glass and plastics, which are used only for visible or near-infrared lights

Summary

Introduction

In recent years, infrared (IR) optical systems are increasingly demanded in many fields such as security and remote sensing. Single-crystal silicon is a typical substrate material for IR optics because of its high transmittance in the IR region. Spherical and aspherical lenses of single-crystal silicon have been used in IR optical systems so far [1,2,3], the silicon lens with its more complex shapes is in demand for future IR optical systems. A microlens array can focus light on photodiodes in image sensors and homogenizers [4,5,6]. Microlens arrays have been widely used in optical systems but currently most of them are made of glass and plastics, which are used only for visible or near-infrared lights. There is very little literature on the fabrication of microlens arrays for IR systems

Methods

Results

Conclusion