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Proceedings Paper

Ultrafast laser with an average power of 120 W at 515 nm and a highly dynamic repetition rate in the MHz range for novel applications in micromachining
Author(s): F. Harth; M. C. Piontek; T. Herrmann; J. A. L'huillier
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Paper Abstract

A new generation of resonant scanners in the kHz-range shows ultra-high deflection speeds of more than 1000m/s but suffer from an inherent nonlinear mirror oscillation. If this oscillation is not compensated, a typical bitmap, written point by point, would be strongly distorted because of the decreasing spot distance at the turning point of the scanning mirror. However, this can be avoided by a dynamic adaption of the repetition rate (RR) of the ultrafast laser. Since resonant scanners are operated in the 10 kHz-range, this means that the RR has to be continuously swept up to several 10 000 times per second between e.g. 5MHz and 10 MHz. High-speed continuous adaption of the RR could also optimize laser micromachining of narrow curved geometries, where nowadays a time consuming approximation with numerous vectors is required. We present a laser system, which is capable of sweeping the RR more than 32 000 times per second between 5MHz and 10MHz at an average output power of more than 120W at 515nm with a pulse duration of about 40 ps. The laser consists of a semiconductor oscillator, a 3-stage fiber pre-amplifier, a solid state InnoSlab power amplifier and a SHG stage. We systematically analyzed the dynamic of the laser system as well as the spectral and temporal behavior of the optical pulses. Switching the repetition rate typically causes a varying pulse energy, which could affect the machining quality over one scanning line. This effect will be analyzed and discussed. Possible techniques to compensate or avoid this effect will be considered.

Paper Details

Date Published: 16 March 2016
PDF: 10 pages
Proc. SPIE 9726, Solid State Lasers XXV: Technology and Devices, 972612 (16 March 2016); doi: 10.1117/12.2212919
Show Author Affiliations
F. Harth, Photonik-Zentrum Kaiserslautern e.V. (Germany)
Research Ctr. Optimas (Germany)
M. C. Piontek, Photonik-Zentrum Kaiserslautern e.V. (Germany)
Research Ctr. Optimas (Germany)
T. Herrmann, Photonik-Zentrum Kaiserslautern e.V. (Germany)
Research Ctr. Optimas (Germany)
J. A. L'huillier, Photonik-Zentrum Kaiserslautern e.V. (Germany)
Research Ctr. Optimas (Germany)

Published in SPIE Proceedings Vol. 9726:
Solid State Lasers XXV: Technology and Devices
W. Andrew Clarkson; Ramesh K. Shori, Editor(s)

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