Measuring Topological Charge of Laguerre–Gaussian Beams With a Y-Shaped Aperture

We study the diffraction pattern of a Laguerre–Gaussian (LG) beam passing through a Y-shaped aperture (YA), which can be used to measure the topological charge (TC) of such a beam. This letter confirms that the magnitude and sign of the TC of the LG beam can be measured with a YA. We also study the effect of the YA with different sizes on the diffraction pattern. In addition, YA diffraction itself can be used to verify the measurement results of the sign of TC. The experimental results agree well with the simulation results. The method is simple and reliable.