BEAM SHAPING


observed similar levels of uniformity throughout the bulk of the material, and with minimal variation in the inlet and outlet hole diameters (Figure 4).


With only a single pulse required per modification this technique allows for substantially faster processing times, whilst also offering the ability to process thicker glass substrates with high aspect ratios; currently we have achieved aspect ratios of 1:40.


CONCLUSION


Figure 2: Schematic diagram of the proposed 3D beam shaping solution to produce a uniform on-axis intensity profile from a QBB by exploiting the fact that the radial intensity incident on the axicon is proportional to the axial intensity within the QBB. Refractive optics reshape the input Gaussian beam into a desired transverse profile.


Figure 3: (a) Cross section of microchannels laser inscribed and etched in fused silica with modified Bessel beam with increasing pulse energy. (b) Comparison between the etched feature width vs depth for both standard and modified Bessel beam.


Modifications were made using both a standard quasi-Bessel beam, and a modified Bessel beam, with a unform axial intensity distribution spanning ~800 µm, which were subsequently analysed after selective chemical etching in NaOH for 24 hrs (Figure 3).


Figure 4: Etched through holes in 1 mm thick fused silica substrate, generated by single picosecond pulses with modified Bessel beam. (a) Top surface, (b) bottom surface (c) cross section of hole profile.


Features made with the standard Bessel show significant variation in the hole width along the propagation direction, consistently following the asymmetric intensity. In contrast, the modified Bessel produced features with a significantly more uniform modification observed over a several hundred-micron range, hole dimeter of ~20 µm for ~700 µm.


We extend this work to the fabrication of through-holes in 1 mm thick fused silica samples. We


Modified Bessel beams provide a simple and intuitive method to generate arbitrary circularly symmetric axial intensity profiles. Here we show one example of a uniform intensity over an extended focal depth, allowing for minimal taper high-aspect ratio modifications in glass to be fabricated. Taking advantage of the extended focal depth afforded by quasi-Bessel beams, with their spot size invariance, it is possible to laser inscribe thicker glass substrates with a single pulse, drastically reducing laser processing times and increasing productivity. We envisage this beam-shaping approach being extended to other applications such as laser welding, waveguide inscription, and various applications which require the use of volumetric processing in transparent materials.


REFERENCES [1] C. Yu, et al. Sensors, 24 (2024) 171.


[2] D. Franz, D. et al. Optics and Lasers in Engineering, 193 (2025) 109106.


[3] A.S. Rao. Physica Scripta, 99 (6) 062007 (2024).


[4] M. Duocastella, C.B. Arnold. Laser & Photonics Reviews, 6, 607-621 (2012).


[5] O. Brzobohatý, et al. Opt. Express, 16 (2008) 12688–12700.


Jag5@hw.ac.uk www.hw.ac.uk


Jakob Gueye is a final year PhD student in the Applied Optics and Photonics group (AOP) at Heriot- Watt University.


LASER USER 119 MARCH 2026 | 23


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32