Focusing of tightly focused azimuthally polarized double ring beam by a lens in the presence of coma aberration

Abstract

The intensity distribution of azimuthally polarized double ring beam through high numerical aperture objective lens in the presence of coma has been studied based on the vector diffraction theory. It is shown that in the focusing of azimuthally polarized double ring beam through high numerical aperture objective lens, a uniform dark channel with a quite long depth of focus is obtained in the absence of coma aberration. This dark channel has many applications in atom optical experiments such as atomic lenses, atom traps and atom switches. Investigation results show that the presence of coma aberration in the focusing objectives generates focal structure modification with positional shift of the generated focal structure which affects the image quality seriously and disappearance of the dark channel.