Ultrafast z-scanning for high-efficiency laser micro-machining

Ting-Hsuan Chen,Craig B Arnold,Romain Fardel

doi:10.1038/lsa.2017.181

Abstract

High-throughput laser micro-machining demands precise control of the laser beam position to achieve optimal efficiency, but existing methods can be both time-consuming and cost-prohibitive. In this paper, we demonstrate a new high-throughput micro-machining technique based on rapidly scanning the laser focal point along the optical axis using an acoustically driven variable focal length lens. Our results show that this scanning method enables higher machining rates over a range of defocus distances and that the effect becomes more significant as the laser energy is increased. In a specific example of silicon, we achieve a nearly threefold increase in the machining rate, while maintaining sharp side walls and a small spot size. This method has great potential for improving the micro-machining efficiency of conventional systems and also opens the door to applying laser machining to workpieces with uneven topography that have been traditionally difficult to process.

Highlights

The ability to laser machine materials with high resolution and high throughput is critical in advanced manufacturing for a vast array of applications, from photovoltaic cells to bio-compatible microcomponents[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
The surface of the workpiece has to be carefully maintained within the focal position of the laser beam to ensure a high efficiency; as material is removed, it is important to continue to adjust the location of the laser focus to follow the change in topography of the workpiece[16]
To meet the growing demand for micro-machined products, such as photovoltaic cells, electronic devices, and medical micro-elements, we demonstrate a new high-efficiency laser machining method enabled by an ultrafast z-scanner

Summary

Introduction

The ability to laser machine materials with high resolution and high throughput is critical in advanced manufacturing for a vast array of applications, from photovoltaic cells to bio-compatible microcomponents[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] The precision of these manufacturing techniques relies on focusing a laser beam to a micron-sized spot onto the surface of the workpiece. One common method used to mitigate a narrow vertical machining range consists of extending the DOF of the system by using, for example, a low focusing power lens or structured light Such attempts lead to a significant loss in lateral resolution[17]. In addition to the difficulty of real-time surface monitoring, most controlled focusing methods suffer from low response rates compared to the repetition rate of the laser[16,18,19,20,21,22,23,24,25]

Methods

Results

Conclusion