Tight focusing properties of phase modulated azimuthally polarized doughnut Gaussian beam

The intensity distribution in the focal region of a high NA lens for the incident azimuthally polarized doughnut Gaussian beam transmitted through a multi belt spiral phase hologram (MBSPH) is studied on the basis of the vector diffraction theory. Here we report a new method that generates a needle of transversely polarized light beam with sub diffraction beam size of 0.48λ that propagates without divergence over a long distance of about 49λ in free space and designed a dedicated MBSPH to generate multiple focal spot of transversely polarized. The authors also expect such a light needle of transversely polarized beam may find its application when using optical materials or instruments responsive to the transversal field only and to use in multiple optical trapping.