Optical Momentum, Spin, and Angular Momentum in Dispersive Media

Area of Science:

• Optics and Photonics
• Condensed Matter Physics
• Electromagnetism

Background:

• Understanding the momentum, spin, and orbital angular momentum of optical fields is crucial for describing light-matter interactions.
• Existing formalisms face challenges, particularly the Abraham-Minkowski dilemma and the distinction between kinetic and canonical descriptions.

Purpose of the Study:

• To develop a unified theoretical framework for analyzing the momentum, spin, and orbital angular momentum of structured monochromatic optical fields.
• To resolve ambiguities in existing theories, specifically the Abraham-Minkowski dilemma and the kinetic versus canonical pictures.

Main Methods:

• Examination of momentum, spin, and orbital angular momentum in dispersive, inhomogeneous, isotropic media.
• Introduction of novel canonical Minkowski-type momentum, spin, and orbital angular momentum densities.
• Application of the general theory to inhomogeneous surface plasmon-polariton (SPP) waves.

Main Results:

• The kinetic Abraham momentum is shown to describe energy flux and group velocity.
• Novel canonical Minkowski-type momentum, spin, and orbital angular momentum densities are introduced, offering advantages over previous methods.
• Surface plasmon-polaritons (SPPs) exhibit a "supermomentum" and a transverse spin whose sign depends on frequency.

Conclusions:

• The developed theory provides a natural and advantageous framework for understanding optical angular momentum in complex media.
• The findings offer new insights into the properties of surface plasmon-polaritons, including their unique momentum and spin characteristics.