High fidelity and high efficiency shaping of axially configurable Bessel beams for laser material processing

Adaptive Optics serves as a precise and facile means of laser beam shaping that is opening new directions for three-dimensional nano-structuring inside of transparent materials. A Fourier synthesis method in shaping generalized Bessel beams was employed in optical simulation and replicated in experimental characterization. The beam shaping approach generated precise sub-micrometer transverse dimensions scaling to 400-800 nm diameter Bessel beam filaments and demonstrated high fidelity control over axial intensity profile such as flat, sine wave, and parabolic shapes. The beam shaping approach is applicable to other forms of diffraction-less beams such as helical and Matthieu beams. The application of variational calculus approaches in the spatial light modulator phase optimization algorithm facilitated record diffraction efficiencies in a range of ~20 to 50%. The practical demonstration relied on application of Zernike aberration correction to compensate for astigmatism and other aberration in the source laser beam (515 nm) and the optical system.