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 \(\lambda \)) that propagates without divergence over a long distance (of about 14 \(\lambda \)) in free space. The author expect such investigation is worthwhile for the applications of the optical manipulation, optical microscopy and optical micromachining.