Simulation of the Propagation of Rotating Laguerre–Gaussian Beams in an Imaging System with an Obstacle

Two imaging systems are considered in this paper: a system with a lens containing an obstacle in the front focal area of the lens, and a system with an image in the front focal area of the lens with a phase mask and a circular aperture diaphragm. A rotating Laguerre–Gaussian beam propagates through the first imaging system, and structure of the beam transforms after propagation through an obstacle. The simulations of the system were performed using Fresnel transformations for the field propagation before and after the lens. The simulation results showed how much the beam is distorted at the output of the imaging system depending on the size of the obstacle and its distance from the propagation axis. Similarly, a rotating Laguerre–Gaussian beam with a superimposed “triangle” shadow image propagates through the second system. The simulations were performed using the Fresnel transform and overlaying a limiting aperture in the lens plane in order to investigate the influence of the aperture size on the sharpness of the generated image.