Trajectory-Based Unveiling of Angular Momentum of Photons

TL;DR

This paper investigates the average photon trajectories (APTs) of photons with spin and orbital angular momentum, revealing complex spiral behaviors and longer travel distances, enhancing understanding of photon motion in quantum systems.

Contribution

It introduces a novel analysis of APTs for photons with SAM and OAM, including helicity concepts, and clarifies their complex three-dimensional spiral structures and coupling effects.

Findings

APTs exhibit spiral structures influenced by SAM and OAM.

Photon travel distance can be significantly longer than geometric distance.

Helicity and differential helicity help unveil 3D spiral behaviors.

Abstract

The Heisenberg uncertainty principle suggests that it is impossible to determine the trajectory of a quantum particle in the same way as a classical particle. However, we may still yield insight into novel behavior of photons based on the average photon trajectories (APTs). Here we explore the APTs of photons carrying spin angular momentum (SAM) and/or orbital angular momentum (OAM) under the paraxial condition. We define the helicity and differential helicity for unveiling the three-dimensional spiral structures of the APTs of photons. We clarify the novel behaviors of the APTs caused by the SAM and OAM as well as the SAM-OAM coupling. The APT concept is very helpful for profoundly understanding the motion of trapped particles and for elucidating other physical systems. Due to the presence of the helical path caused by the SAM and/or the OAM, the actual traveling distance of the photons might be much longer than the geometric distance.