Beam shaping is commonly applied in laser micromachining or materials-processing applications to modify the Gaussian distribution from a laser to a tophat or other profile depending on the task at hand. But more and more, adaptive-optic (AO) elements such as piezoelectric deformable mirrors and liquid-crystal spatial light modulators (SLMs) are being used to rapidly modify the mode shape of a laser beam at up to kilohertz speeds.

Liquid-crystal-based SLMs have high resolution and can produce complex and arbitrary beam shapes. They do, however, have a lower power threshold (typically tolerating a few watts per square centimeter) and slower modulation capabilities—tens of hertz versus kilohertz—than deformable mirrors. Heriot-Watt University (Edinburgh, Scotland) researchers have demonstrated increased power handling of such a device and have applied it to laser-marking applications using a 14.7 W nanosecond laser. Using a 19.5 × 14.6 mm Holoeye (Berlin-Adlershof, Germany) reflective SLM with 1024 × 768 pixels at 75 Hz, complex shapes can be marked on stainless-steel and other surfaces. Image quality was improved by modifying the phase profile during the marking process.

Contact Jonathan Parry at j.parry@hw.ac.uk.

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