Materials processing using unconventional ultrafast laser beams

Research activities

In the late 90s, it was predicted that tubular, radially-polarized laser beams can cut materials much more efficiently and accurately than conventional laser beams thus offering significant economic and environmental benefits. Since then, the crucial advantages of radial polarization (Fig. 1) over other homogeneous states of polarization (i.e., linear, elliptical, circular) both in cutting efficiency and quality have been experimentally confirmed using continuous wave (CW) and nanosecond (or longer) pulse lasers in various micromachining applications. Long pulse and CW laser systems generating radially polarized beams are now being actively introduced to several high-end manufacturing processes.

However, there is a whole range of micromachining, medical and biological applications in which only ultrashort laser pulses can be used due to their ability to process any substance with accuracies and resolutions going below the range of the laser wavelength. The key role of light polarization in ultrashort pulse-matter interaction is now widely recognized and various polarization-related effects are being actively studied. With a very rare exception, these studies have concentrated so far on standard Gaussian beams with homogeneous states of polarization, namely linear and circular polarization.

Fig. 2. Polarization-sensitive micro-optic structures produced inside fused silica substrates with multiple radially polarized (right) and azimuthally polarized (left) femtosecond laser pulses. Bottom images: A cross-polarized light view (left) of a 2-D array of polarization imprints in bulk material (right). Note that the nanostructures shown in the top SEM images grow exactly perpendicular to the light polarization. These sub-wavelength architectures are the finest regular structural changes that can be produced by light inside a pure transparent material.

The goal of this research project is to show that ultrashort pulse laser beams with complex polarization and intensity structure can expand functionalities of the existing ultrafast laser micromachining technology by increasing its efficiency and precision. The enabling technology has already been demonstrated in a series of our recent publications (Fig. 2 and references below). We are planning to use these unconventional light pulses to process materials relevant to semiconductor and biomedical industry and also conduct studies on dissecting biological tissues, specifically in vitro porcine and/or bovine corneas.

Selected publications

• C. Hnatovsky, V. G. Shvedov, and W. Krolikowski. The role of light-induced nanostructures in femtosecond laser micromachining with vector and scalar pulses, Opt. Express 21, 12651-12656, (2013).
• V. G. Shvedov, C. Hnatovsky, N. Shostka, and W. Krolikowski. Generation of vector bottle beams with a uniaxial crystal. J. Opt. Soc. Am. B 30, 1-6 (2013).
• C. Hnatovsky, V. Shvedov, N. Shostka, A. Rode, W. Krolikowski. Polarization-dependent ablation of silicon using tightly focused femtosecond laser vortex pulses. Opt. Lett. 101, 226-228 (2012).
• C. Hnatovsky, V. Shvedov, W. Krolikowski, A. V. Rode. Revealing Local Field Structure of Focused Ultrashort Pulses. Phys. Rev. Lett. 106, 123901 (2011).
• C. Hnatovsky, V. G. Shvedov, W. Krolikowski, A. V. Rode. Materials processing with a tightly focused femtosecond vortex laser pulse. Opt. Lett. 35, 3417-3419 (2010).
• V. Shvedov, C. Hnatovsky, W. Krolikowski, A. Rode. Efficient beam converter for the generation of high-power femtosecond vortices. Opt. Lett. 35, 2660-2662 (2010).
• R. S. Taylor, E. Simova, C. Hnatovsky. Creation of chiral structures inside fused silica glass. Opt. Lett. 33, 1312-1314 (2008).
• R. S. Taylor, C. Hnatovsky, E. Simova. Applications of femtosecond laser induced self-organized planar nanocracks inside fused silica glass. Laser and Photonics Reviews 2, 26-46 (2008).

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