Ultrafast lasers are enabling precision machining of a wide variety of materials. However, the optimal laser parameters for proper material processing can differ greatly from one material to another. In order to cut high aspect-ratio features at high processing speeds the laser parameters such as pulse energy, repetition rate, and cutting speed need to be optimized. In particular, a shorter pulse duration plays an important role in reducing the thermal damage in the Heat-Affected Zones. In this paper we present a novel ps fiber laser whose electronically tunable parameters aim to facilitate the search for optimal processing parameters. The 20W 1064nm Yb fiber laser is based on a Master Oscillator Power Amplifier (MOPA) architecture with a repetition rate that can be tuned continuously from 120kHz to 120MHz. More importantly, the integration of three different pulse generators enables the pulse duration to be switched from 25ps to 50ps, or to any value within the 55ps to 2000ps range. By reducing the pulse duration from the ns-regime down to 25ps, the laser approaches the transition from the thermal processing regime to the ablation regime of most materials. Moreover, in this paper we demonstrate the synchronization of the pulses from two such MOPA lasers. This enables more elaborate multipulse processing schemes where the pulses of each laser can be set to different parameter values, such as an initial etching pulse followed by a thermal annealing pulse. It should be noted that all the laser parameters are controlled electronically with no moving parts, including the synchronization.
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Alexandre Dupuis ; Bryan Burgoyne ; Guido Pena ; André Archambault ; Dominic Lemieux, et al.
Synchronized ps fiber lasers with pulse durations (25, 50, 100-2000ps) and repetition rates (100kHz-150Mhz) continuously tunable over three orders of magnitude
", Proc. SPIE 8601, Fiber Lasers X: Technology, Systems, and Applications, 860137 (March 22, 2013); doi:10.1117/12.2005275; http://dx.doi.org/10.1117/12.2005275