Generation of Bessel beams from a diffractive ring lens

A method to generate a diffractive ring lens by a spatial light modulator is proposed. The diffractive ring lens is used to focus a Gaussian beam into single ring or multi-rings firstly. It was found that the transformed beam exhibits a Bessel transverse profile over the focal length, but the spot size is enlarged with the increase of propagation distance, allowing for generation Bessel beams with a ring lens.