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Journal Articles EPL - Europhysics Letters Year : 2022

Frequency changes during the propagation of a light beam

Janine Emile


The energy and therefore the frequency of electromagnetic fields are quantities which are generally considered to be conserved in free space propagation. However, we observe here a frequency varying optical wave in free space propagation. The light comes from an Arago spot. Its frequency changes due to the rotational Doppler effect. More precisely, the light diffracted by a two-dimensional asymmetric object carries orbital angular momentum that varies with distance. As the object rotates, the frequency of the diffracted light experiences different rotational Doppler shifts along propagation. It varies in a discrete quantized way as it propagates. It can be adjusted, without violation of the conservation of energy. Since this phenomenon is deeply rooted in the diffraction process, it shines some new light on this still open issue.
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hal-03903383 , version 1 (16-12-2022)



Olivier Emile, Janine Emile. Frequency changes during the propagation of a light beam. EPL - Europhysics Letters, 2022, 139 (3), pp.35001. ⟨10.1209/0295-5075/ac7dfa⟩. ⟨hal-03903383⟩
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