Realization of higher order vector Bessel beams for transparent material processing applications

Non-diffracting Bessel beams and its modified versions are widely used in industry for transparent material micro processing purposes - cutting, drilling etc., due to generation of high aspect ratio micro voids. More and more applications of such beams involve manipulation of their transverse intensity profile to create unique tools for novel micro processing applications, for example, asymmetric and multi-peak transverse profiles create directional strain and crack in modified area for glass cutting, while other intensity patters may be used to create complex structures in multiphoton polymerization applications. In this work we demonstrate experimental generation of higher order vector Bessel beams which are notable for their ring-shaped transverse intensity profile together with multi-peak transverse polarization components, where ring diameter and number of peaks in separate polarization components depends on beams order. These unique beams were realized using axicon together with higher order s-plates - spatially variant waveplates based on femtosecond laser written nano gratings in fused silica glass substrates. Induced nanogratings withstands high intensity laser radiation without changing its spatial structure which allows us to use nanograting based elements for ultra-short high-power pulsed laser beam shaping. Generated higher order vector Bessel beams and their separate polarization components were used to inscribe modifications in transparent materials and to investigate beam`s applicability for ultra-fast laser micro processing purposes.