Paraxial orbital angular momentum beam under misaligned detection

Area of Science:

• Optical physics
• Quantum optics
• Beam propagation

Background:

• Laguerre-Gaussian (LG) beams carry orbital angular momentum (OAM).
• Beam misalignment, including tilt and lateral displacement, can distort the OAM spectrum.
• Understanding these distortions is crucial for OAM-based applications.

Purpose of the Study:

• To develop an analytical framework for modeling OAM spectra of LG beams under misalignment.
• To investigate the impact of tilt and lateral displacement on OAM sidebands.
• To explore methods for mitigating crosstalk caused by misalignment.

Main Methods:

• Analytical modeling of OAM spectrum detection.
• Mathematical formulation of misalignment effects (tilt and lateral displacement).
• Analysis of dimensionless parameters governing OAM sideband generation.

Main Results:

• Both tilt and lateral displacement generate OAM sidebands with a similar functional form.
• A dimensionless parameter, dependent on beam size and wavelength, characterizes these sidebands.
• Increasing the topological charge (azimuthal index) broadens the OAM spectrum.
• Perpendicular orientation of tilt and displacement leads to destructive interference, reducing crosstalk.

Conclusions:

• The developed framework accurately models OAM spectrum distortions due to misalignment.
• Topological charge significantly influences spectral broadening.
• Destructive interference offers a method to control and reduce crosstalk in misaligned OAM beams.