Nondiffracting approximated Bessel beam (J1)

Abstract

The nondiffracting J0 Bessel beam will be useful in spot welding, particle beam collimation and concentration, tracking, and precision alignment. The J1 beam, the first-order Bessel beam of the first kind, is also a nondiffracting beam and has a potential use in particle beam collimation or concentration. This J1 beam is simulated by using a Fourier transform lens and an annular slit, a part of which is phase retarded. A thin glass plate, covering part of the annular slit, was used for phase retardation. In essence, we simulated polygon-type slits instead of an annular slit based on the double slit interference approach. The nondiffracting hollow cylindrical beam thus obtained shows an intensity profile similar to the beam. The maximum distance of the diffraction-free propagation, as well as the intensity profile, is compared with computer simulations. There is a considerable energy loss in generating the J1 beam. We employed a holographic amplification technique to make the conversion very efficient (50%) and used holographic phase conjugation to extend the nondiffracting distance. Holographic averaging for circular symmetry was used to more closely approximate J1.