Paraxial orbital angular momentum beam under misaligned detection

Abstract

This work presents an analytical framework for modeling a detected orbital angular momentum (OAM) spectrum of a Laguerre-Gaussian (LG) beam subject to tilt and lateral displacement. Firstly, we demonstrate that both types of misalignment generate OAM sidebands governed by the same functional form, each characterized by a distinct dimensionless parameter that depends on the beam’s size and wavelength. Secondly, our analysis reveals that increasing the LG beams azimuthal index (its topological charge) broadens the detected OAM spectrum. Lastly, we show that when both tilt and lateral displacement are present, the contribution of the original OAM mode can be tuned: specifically, by orienting the tilt and displacement in perpendicular directions, the resulting misalignment effects interfere destructively, thereby reducing crosstalk.