Position measurement of non-integer OAM beams with structurally invariant propagation

Area of Science:

• Optics and Photonics
• Quantum Optics
• Beam Propagation

Background:

• Orbital angular momentum (OAM) in light beams enables advanced applications.
• Generating and controlling OAM beams, especially with non-integer values, presents challenges.
• Existing methods for OAM beam generation and measurement can be complex and require intricate calibration.

Purpose of the Study:

• To design a novel method for generating structurally propagation invariant light beams with non-integer orbital angular momentum (OAM).
• To simplify the calibration process for beam positional measurements using quadrant detectors.
• To investigate the influence of OAM value and Hermite-Laguerre-Gaussian (HLG) mode orientation on quadrant detector response.

Main Methods:

• Utilizing Hermite-Laguerre-Gaussian (HLG) modes for beam generation.
• Developing a technique that fixes beam symmetry axes while varying OAM.
• Analytical and experimental validation of the proposed method and detector response.

Main Results:

• Successfully generated propagation invariant light beams with non-integer OAM.
• Demonstrated that fixed symmetry axes simplify quadrant detector calibration.
• Showed that both OAM value and HLG mode orientation significantly affect quadrant detector response.
• Identified limitations of the assumption of quadrant detector peak sensitivity at the beam center for anisotropic beams.

Conclusions:

• The proposed HLG-based design offers a simplified approach to generating and measuring non-integer OAM beams.
• Quadrant detector calibration for anisotropic beams requires consideration of both OAM and mode orientation.
• This work advances the understanding and practical application of OAM light beams.