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Analysis of misaligned optical rotational Doppler effect by modal decomposition.
Optics Express
|May 14, 2021
Summary
A new method analyzes the misaligned optical rotational Doppler effect (RDE) using orbital angular momentum (OAM) decomposition. This technique accurately determines object rotation frequency from broadened RDE spectra, enhancing remote sensing and metrology applications.
Area of Science:
- Optics and Photonics
- Metrology
- Remote Sensing
Background:
- The optical rotational Doppler effect (RDE) is linked to the orbital angular momentum (OAM) of optical vortices.
- Misaligned optical vortices lead to a broadened RDE frequency spectrum.
Purpose of the Study:
- To propose and validate a method for OAM modal decomposition of misaligned optical RDE.
- To analyze how lateral displacements and angular deflections affect OAM mode distribution.
- To enable faster and more accurate object rotation frequency determination.
Main Methods:
- Development of an OAM modal decomposition technique for misaligned RDE.
- Inner product computation to derive the OAM spectrum (relative intensity of OAM modes).
- Experimental validation using a superimposed Laguerre-Gaussian (LG) vortex and analyzing the frequency shift spectrum.
Main Results:
- Misaligned LG vortices can be expressed as combinations of coaxial LG modes.
- Lateral displacements and angular deflections alter OAM mode distribution relative to the rotation axis.
- Experimental results show discrete signals in the expanded spectrum, matching theoretical predictions.
Conclusions:
- The proposed method provides a comprehensive analysis of misaligned optical RDE.
- The difference between adjacent signal peaks in the spectrum allows for rapid and precise rotation frequency measurement.
- This technique holds significant potential for applications in remote sensing and optical metrology.
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