Creation of super-long bright channel using high NA lens axicon with dedicated multibelt binary phase mask

Abstract

We provide a theoretical approach to use a multibelt binary phase mask in combination with a high numerical aperture lens axicon to achieve a subwavelength focal spot with large uniform focal depth when illuminated by an azimuthally polarized Laguerre-Gaussian beam. The intensity distributions are derived and evaluated based on the vector diffraction theory. Here we report a new method that generates a transversely polarized light beam with sub diffraction beam size (0.384 λ) that propagates without divergence over a long distance (of about 14 λ) in free space. The author expect such investigation is worthwhile for the applications of the optical manipulation, optical microscopy and optical micromachining.