INVESTIGATION OF ENERGY CHARACTERISTICS LIMITED FOCUSED NEEDLE BEAMS WITH LONGITUDINAL POLARIZATION
A comparative analysis of spatial variations in the energy characteristics of longitudinally polarized, extremely focused, needle laser beams generated by an optical system with selective thin-film transformation of the linear polarization of the beams into the radial one, followed by their subsequent spatial filtering and sharp ring focusing to subwave sizes. For the important special case of ideal radial polarization of a focused beam, longitudinal sections of spatial distributions of the electric energy density and the Poynting vector modulus in the vicinity of the focus were compared by numerical simulation. It is shown that the degree of their difference increases substantially with decreasing angular zone of ring focusing and with the introduction of space-frequency filtering. It is established that the dimensions of the axial zone of beam focusing determined for their central lobes in the first approximation do not depend on the energy characteristics in which they are measured.