Optical Bessel-like Beams with Engineered Axial Phase and Intensity Distribution

Abstract: Bessel beams are known for their property of maintaining propagation-invariant transverse intensity distribution. The true Bessel beams has unlimited energy, however the experimental realization of limited energy Bessel-like beams provides almost diffraction-free beams over a certain distance. These beams are applicable to microfabrication, particle manipulation etc. where long and narrow intense beam is needed. A type of laser beams that maintains narrow intensity peak for long distances are often called optical needles. In this paper we propose a construction of an optical needle using a superposition of vector Bessel beams and for flexible engineering of axial intensity profile. We investigate both theoretically and experimentally generation of various optical beams of different axial profiles, lengths, beam widths etc. We use a spatial light modulator as a toy model of an optical element to shape the spatial spectrum of the beam. Moreover, we demonstrate distortions introduced into the optical needle by a planar interface between two dielectric media: spherical aberration and astigmatism due to the nonzero inclination angle and discuss ways to correct them.