Gaussian mode component of Laguerre-Gaussian beams obstructed by symmetric angular masks

Abstract

We measure the Gaussian component of an LG beam immediately after it is obstructed by N symmetrically arranged pie-shaped angular masks. Numerical calculations based on the overlap integral show that the Gaussian component is detected only when the ratio between the LG mode l and the number of angular masks N is a whole integer ranging from 0 to l. Detection is most sensitive when the angular size of each mask is π/l. The number of Gaussian mode peaks observed corresponds to the ratio l/N. We implemented an experimental setup to measure the Gaussian component of the obstructed LG beam using a modified phase hologram uploaded onto a spatial light modulator (SLM), enabling simultaneous beam generation and obstruction, and a single-mode fiber (SMF) for detection. For N = l, the detection is most sensitive when the total angular extent of the obstruction is half the phase hologram, which is consistent with the numerical results. Detection of the Gaussian component of an obstructed LG beam provides an effective method for OAM mode probing, with potential applications in optical communications, quantum information processing and precision measurement systems.