Design of diffractive optical elements to suppress the Bessel-Gauss beam generated by reflective off-axis axicon

• Side-lobes suppression for Bessel-Gauss beam generated by reflective axicon. • Computational method for off-axis propagation and diffractive optical element design. • Low side-lobes intensity, i.e., the energy of the side-lobes is lower than 0.8%) • Only one iteration is sufficiency to design the diffractive optical element. A phase updating algorithm is proposed to design a diffractive optical element (DOE) to suppress the side-lobes of the Bessel-Gauss beam generated by the reflective off-axis axicon. Due to the tilt between the incident light and the outgoing light, conventional angular spectrum method (ASM)-based algorithm cannot be directly applied to the calculation of the off-axis Bessel-Gauss beam. To update the phase of the DOE, a novel algorithm is used where non-uniform inverse discrete Fourier transform is employed to calculate the off-axis diffraction. Only one iteration is required to obtain the specified Bessel-Gauss beam. For a Bessel-Gauss beam with a central peak diameter of 21.5 (9.8) μm, we demonstrate a DOE with the side-lobes energy lower than 0.8% and depth of focus (DOF) of 399.1 (100.7) μm, respectively.