BEAM SHAPING


Figure 2: 5 spots parallel drilling of mild steel with varying exposure between 20 s, 10 s and 5 s and power increasing from 20 W to 300 W.


≥100 W. Yet, the first-order diffraction efficiency remained high. At 300 W with 5 s exposure, the evaporated volume rate per spot was 4429 ± 1208 µm³/W/s (100 W: 309 ± 70; 200 W: 2221 ± 690), evidencing efficient material removal alongside stable array formation.


In Figure 3, a vortex mode with topological charge m = 6 produced a distinctive concentric ring structure under a 350 W, 1 s exposure. The pattern showed a degree of hexagonal symmetry, linked to asymmetries in the ring intensity profile, and revealed five distinct microstructural regions. At the centre, within r₁ ≈ 65 μm, individual micro-crystals were observed, surrounded by a reflective zone extending to r₂ ≈ 290 μm, where radial cracks also formed. Beyond this, three thin concentric rings extended out to r₅ ≈ 680 μm, with the outer dark, highly oxidised ring corresponding to the beam’s ring intensity diameter of ~1.0 mm. EDX elemental mapping showed manganese enrichment along the rings with complementary oxygen and iron distributions, confirming selective oxidation and compositional redistribution.


When a 300 W, 5 s exposure was applied to molybdenum, which has the third-highest melting point of all metals, the processed area displayed a central golden oxide layer (MoO₃) surrounded by well- defined recrystallisation rings (Figure 4). Microscopy revealed grain growth and clear phase boundaries between the oxidised and recrystallised zones. The results illustrate how shaped beams can be used not only for ablation or melting, but also to deliberately trigger chemical oxidation and microstructural


Figure 3. EDX analysis of vortex beam drilling (m=6) on stainless steel with 350 W/1 s exposure.


transformations in refractory metals.


FUTURE OUTLOOK


The results presented here demonstrate that liquid- crystal SLMs, once limited to laboratory-scale power levels, can now be operated stably above 350 W. This breakthrough paves the way for their use in a broader range of high-power applications. For example, laser welding could benefit from reduced spatter through optimised energy delivery, while surface treatment and texturing could achieve higher throughput using multi-spot arrays, flat-top and shaped beam profiles. A unique advantage of SLM technology is that it allows the beam shape to be adapted rapidly and on demand. It enables a single system to switch between different processes or optimise the beam in real time for changing conditions.


Figure 4. Optical microscopy images (a, b) and SEM images (c, d) of 300 W, 5 s exposure on molybdenum with vortex ring mode.


Bilton, M., Mirihanage, W., Mativenga, P., Edwardson, S. P., Dearden, G.


Authors' affiliations in [3] REFERENCES


[1] Department for Business and Trade (2025). The UK’s Modern Industrial Strategy 2025, 23 June.


[2] Tang, Y.; et al. Opt. Laser Technol. 2025, 181, 111589.


[3] Zuo, S. et al. Photonics 2025, 12, 544.


Looking ahead, the integration of beam shaping with Industry 4.0 concepts offers exciting possibilities. Recent studies pointed to adaptive optics and real-time optimisation in smart factories [4, 5]. By combining high-power SLMs with closed-loop control and machine learning, future systems could automatically adjust beam profiles in response to process feedback with many potential applications in welding and additive manufacturing. Key steps will be to extend to multi-kilowatt-class lasers, further improve the optical train's thermal resilience, and develop application-specific calibration methods.


* Wang, S., Pulham, C., Tang, Y., Perrie, W., Allegre, O. J., Tang, Y., Sharp, M., Leach, J., Whitehead, D. J.,


[4] Hasegawa, S.; Hayasaki, Y. Opt. Lett. 2009, 34, 22–24.


[5] Buske, P. et al. Opt. Express. 2024, 32, 7064–7078.


Figures reprinted from [3] under the terms of the CC BY.


Shuchen.zuo@manchester.ac.uk manchester.ac.uk


Shuchen Zuo is a PhD researcher in laser-based advanced


manufacturing at the University of Manchester, specialising in surface texturing and beam shaping.


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