Fiber coupling of high-power diode laser stack for direct polycarbonate processing

摘要

We present a novel optical system for fiber coupling of a commercial high power diode laser stack and the application of this laser system to transmission welding of engineering thermoplastics. The diode laser stack is made up of two 20% fill factor bars, emitting at 808 nm and with a total maximum output power of 120W CW. The stack was collimated using FSAC micro-optics lenses in the fast and slow axis, with a full angle divergence of <4mrad and <25mrad respectively. The optical design and simulations were carried out using ZEMAX~. Based on the design we built an optical set up, which is divided in two subsystems. The first one collimates the laser beam in order to achieve the best focus and couple it into the 400μm core fiber with NA0.22 and 70% efficiency. The second subsystem is designed for beam conformation after the fiber output, using collimation and beam shaping to have a Gaussian beam profile on the work piece. The laser system was applied to study the welding of polycarbonate plastics, based on the effects of selected welding parameters on the seam geometry and surface integrity. The quality of the spot welding has been analyzed obtaining welded seams with a mean diameter about 500-600μm, preserving the good technological properties of the thermoplastic considered in this work. The results show that we have successfully developed a novel laser system which is highly efficient for thermoplastics processing.