Lisa Ackermann: Smoothing laser patterns for materials processing

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Last year, Lisa Ackermann already published on beam shaping of high-energy lasers for materials processing by using spatial light modulators (SLMs). As she pointed out, a drawback is the presence of speckle noise, which overlays the shaped intensity structure and drastically reduces the beam quality. It arises from interference of the laser waves and cannot be averaged out over time without reducing efficiency. Instead, the configuration of the SLM surface hit by the laser beam has to vary.

Lisa presents a new approach on that in her two recent publications, High-speed speckle averaging for phase-only beam shaping in laser materials processing and Spot arrays for uniform material ablation with ultrashort pulsed lasers. Similar as in a laser projector known from laser shows, she uses rotary mirrors to scan the laser beam across the active surface of the SLM. Via that, the speckle patterns vanish while the resulting beam structure remains and smoothens. This enables high-quality material ablation.

Lisa Ackermann works at the Institute of Photonic Technologies, her supervisor is Michael Schmidt. The original publications can be found in Optics and Lasers in Engineering and Optics & Laser Technology.

Rotary mirros (lower right) scan the laser across the spatial light modulator (upper left)