Theoretical analysis and experimental verification on optical rotational Doppler effect

TL;DR

This paper develops a theoretical model for the optical rotational Doppler effect, showing how frequency shifts depend on the surface of spinning objects and mode differences, and verifies it experimentally.

Contribution

The paper introduces a comprehensive theoretical model for the optical rotational Doppler effect based on modal expansion, validated through experiments, enhancing understanding of the physical processes involved.

Findings

Frequency shift depends on the surface of the spinning object.

Reduced Doppler shift is linear to mode index difference and rotation speed.

Experimental verification confirms the theoretical predictions.

Abstract

We present a theoretical model to sufficiently investigate the optical rotational Doppler effect based on modal expansion method. We find that the frequency shift content is only determined by the surface of spinning object and the reduced Doppler shift is linear to the difference of mode index between input and output orbital angular momentum (OAM) light, and linear to the rotating speed of spinning object as well. An experiment is carried out to verify the theoretical model. We explicitly suggest that the spatial spiral phase distribution of spinning object determines the frequency content. The theoretical model makes us better understand the physical processes of rotational Doppler effect, and thus has many related application fields, such as detection of rotating bodies, imaging of surface and measurement of OAM light.