High-rate laser microprocessing using a polygon scanner system

Abstract

This paper discusses results obtained in high-rate laser microprocessing by using a high average power high-pulse repetition frequency ultrashort pulse laser source in combination with an in-house developed polygon scanner system. With the recent development of ultrashort pulse laser systems supplying high average power of hundreds watts and megahertz pulse repetition rates, a significant increase of the productivity can potentially be achieved in micromachining. This permits upscaling of the ablation rates and large-area processing, gaining increased interest of the ultrashort pulse laser technology for a large variety of industrial processes. However, effective implementation of high average power lasers in microprocessing requires fast deflection of the laser beam. For this, high-rate laser processing by using polygon scanner systems provide a sustainable technological solution. In this study, a picosecond laser system with a maximum average power of 100 W and a repetition rate up to 20 MHz was used. In raster scanning using the polygon scanner, the laser beam with a focus spot diameter of 44 μm was deflected with scan speeds of several hundred meters per second. The two-dimensional scanning capability of the polygon scanner supplied a scan field of 325 × 325 mm. The investigations were focused on high-rate large-area laser ablation of technical grade stainless steel as well as selective thin film ablation from bulk substrates. By variation of the processing parameters laser fluence, as well as temporal and spatial pulse-to-pulse distance, their impact onto the ablation process was evaluated with respect to the ablation rate, processing rate, surface quality, and ablation efficiency.