Ultrasonic laser shaping for advanced patterningFriday (26.06.2020) 10:10 - 10:50 Room 2
Controlling the shape and propagation characteristics of a laser beam enables high-throughput additive and subtractive manufacturing at the micro and nanoscale. Examples include splitting a laser beam into multiple beamlets for parallelized laser writing or using Bessel beams for extended depth-of-field processing. However, current beam shaping strategies such as spatial light modulators or diffractive optical elements can be limited in speed, diffraction efficiency or flexibility in the pattern selection. In this talk, we will describe how ultrasound in liquids can be used to split and shape a laser beam at unprecedented speeds. The gist of our approach is to combine two ultrasonic resonant cavities in series. Each cavity contains piezoelectric transducers that induce vibrations in a liquid, causing the periodic modulation of the liquid refractive index. The first cavity has a cylindrical symmetry and enables the shaping of an incident Gaussian beam into a Bessel, annular or Gaussian beam depending on the amplitude, phase or frequency of the ultrasonic waves. The second cavity has a squared symmetry[2-3], acting as a phase grating and splitting a laser beam into multiple beamlets whose number, position and intensity can be controlled with the ultrasound parameters. Because no bulky mechanical moving parts are involved, aligning and synchronizing the two cavities enables dynamic generation of tunable arrays of Gaussian, Bessel, and annular beamlets at sub-microsecond time scales. Integrating such a system with a laser direct-writing workstation leads to the large area micro and nano-pattering of metals, polymers, and ceramics. As our results demonstrate, the combination of ultrasound and liquids offers a promising approach to overcome the classical trade-off between throughput and design flexibility of laser writing systems, paving the way for optimizing laser processing efficiency via “on-the-fly” shaped light.
 M. Duocastella and C. B. Arnold, “Enhanced depth of field laser processing using an ultra-high-speed axial scanner,” Appl. Phys. Lett., vol. 102, no. 6, p. 061113, 2013.
 A. Zunino, S. Surdo, and M. Duocastella, “Dynamic Multifocus Laser Writing with Acousto-Optofluidics,” Adv. Mater. Technol., vol. 1900623, pp. 1–7, 2019.
 S. Surdo and M. Duocastella, “Fast Acoustic Light Sculpting for On-demand Maskless Lithography,” Adv. Sci., vol. 6, p. 1900304, 2019.
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