Generation of modified Bessel-Gauss beam with low side-lobes and large depth of focus using multiphase plate

The high side-lobes of the Bessel-Gauss beam generated by refractive axicon or reflective axicon is a major factor that hinders its practical application. In this paper, multiphase plate is used to modify the Bessel-Gauss beam, which can suppress the side-lobes and retain the diffraction-free property over a certain length. The radii parameters and the phase in each ring are optimized using genetic algorithm. By changing the circular rings in the multiphase plate optimized for refractive axicon into the elliptical rings according to the off-axis angle of the reflective axicon, side-lobe suppression for the reflective axicon can also be achieved without redesigning the multiphase plate. Simulation results show that side-lobes of less than 2% and depth of focus of similar to 15 mm can be obtained with proper choice of parameters.