Controllable Spatial Array of Bessel-like Beams with Independent Axial Intensity Distributions for Laser Microprocessing

Bessel beams generated via axicons are widely used for various applications like optical tweezers or laser microfabrication of transparent materials. The specific intensity profile having high aspect ratio of beam width and length in turn generates high aspect ratio void that resembles a needle. In contrast to commonly generated Bessel beam that has a fixed axial intensity distribution. We present a novel method to engineer an optical needle that can have an arbitrary axial intensity distribution via superposition of different cone angle Bessel beams. We analytically describe spatial spectra of an optical needle having arbitrary axial intensity distribution. We also demonstrate a superposition of independent optical needles and analyze the physical limitations to observe well separated optical needles as they are influence by mutual interference of the individual beams. In order to verify our theoretical and numerical results we generate controllable spatial arrays of individual beams with various numbers and spatial separations by altering a spectrum of incoming laser beam via spatial light modulator. Lastly, we numerically examine distortions caused by propagation through planar air-dielectric interface and show compensation method by appropriately modifying spectral masks.