Rotational Doppler effect in left-handed materials

TL;DR

This paper explains the rotational Doppler effect in left-handed materials, highlighting its unreversed nature and the underlying physics involving negative phase velocity and wave-front inversion.

Contribution

It provides a theoretical analysis of the rotational Doppler effect in LHMs, revealing unique behaviors and angular momentum transfer mechanisms.

Findings

Rotational Doppler effect in LHMs is unreversed unlike linear Doppler effect.

The effect causes upstream energy flow in normal dispersion and downstream in anomalous dispersion.

Angular momentum transfer from LHM to light beam is predicted.

Abstract

We explain the rotational Doppler effect associated with light beams carrying with orbital angular momentum in left-handed materials (LHMs). We demonstrate that the rotational Doppler effect in LHMs is unreversed, which is significantly different from the linear Doppler effect. The physics underlying this intriguing effect is the combined contributions of negative phase velocity and inverse screw of wave-front. In the normal dispersion region, the rotational Doppler effect induces a upstream energy flow but a downstream momentum flow. In the anomalous dispersion region, however, the rotational Doppler effect produces a downstream energy flow but a upstream momentum flow. We theoretically predict that the rotational Doppler effect can induce a transfer of angular momentum of the LHM to orbital angular momentum of the beam.