Extending the operational limit of a cooled spatial light modulator exposed to 200 W average power for holographic picosecond laser materials processing

• Published in: Optics and laser technology 2025-02, Vol.181, p.111589, Article 111589
• Main Authors: Tang, Yue, Li, Qianliang, Fang, Zheng, Allegre, Olivier J., Tang, Yin, Perrie, Walter, Zhu, Guangyu, Whitehead, David, Schille, Joerg, Loeschner, Udo, Liu, Dun, Li, Lin, Edwardson, Stuart P., Dearden, Geoff
• Format: Article
• Language: English
• Subjects: Material processing; Multi-beam laser processing; Picosecond laser; Spatial light modulator
• ISSN: 0030-3992
• DOI: 10.1016/j.optlastec.2024.111589

•Operational limit of a cooled spatial light modulator extended from P=110 W to 210 W with picosecond laser exposure.•Binary Damman arrays with π phase range enhance SLM performance, achieving η ∼ 0.77 at 183 W.•Introduction of efficient flat top intensity (FT) generator reduces chip temperature while SLM phase response reaches Δφ> 2π at P=210 W with an 8 x 8 mm FT beam.•Enhanced diffractive performance on stainless steel allows multi-beam ps laser processing efficiency η ∼ 0.89 at 183 W. The phase range of a Spatial Light Modulator (SLM) requires full 2π response for accurate phase modulation of the incident laser wavefront to create the desired structured intensity distribution. While cooled SLM’s allow increased power exposures, degradation in performance occurs with average powers P>100 W in a Gaussian beam due to residual absorption and consequent heating of the liquid crystal (LC) layer which seriously limits the phase stroke and diffraction efficiency. By introducing a refractive flat top intensity generator ahead of a cooled SLM, we have extended the phase range to Δφ = 2π at incident power P=210 W with only a small light field depolarisation. The operational limit has therefore been extended significantly, allowing efficient, parallel laser materials processing with a high-power picosecond laser. The calculation and implementation of binary Damman gratings for multi-beam laser processing is also shown to be useful at high power exposure.