The radial Doppler effect of optical vortex beams induced by a surface with radially moving periodic structure

Abstract

Recent studies have highlighted that the rotational Doppler effect arises from rotational motion and optical orbital angular momentum (OAM), which has potential to detect rotating objects. Here, we investigate the frequency shift when an OAM beam is scattered from a surface with a radially periodic structure moving in the radial direction. This kind of frequency shift is related to the radial velocity and the harmonic components of the radially periodic structure of the surface. We support our conclusion by means of calculating time-evolution phase of light beam theoretically and measuring the rotating interference patterns through coherent detection. Furthermore, a more general theoretical model for the complex frequency shift resulting from the concurrence of both the angular and radial Doppler effects, is proposed. The complex frequency shift characteristics are associated with harmonic components and the velocity of the structural surface in both radial and angular directions. Interestingly, the frequency shift resulting from the moving surface may be spatially variant, because of the combination of the angular and radial Doppler effects. This scheme is useful for analyzing the light-moving matter interaction. Meanwhile, it might be applicable to transverse velocity measurement and frequency modulation.

Simple Experiment of Doppler Effect Using Smartphone Microfon Sensor

“…In the rotational and radial moves, Doppler effects should take place simultaneously in the scattered light. The radial Doppler effect can be detected from the time-periodic interference pattern via power detector [30]. Table 1 shows how conformity experiment data is similar to the calculation result data.…”

Rotational Doppler Frequency Shift from Time‐Evolving High‐Order Pancharatnam–Berry Phase: A Metasurface Approach

“…Besides its fundamental relevance, our finding may open a new alternative path for the precise tailoring of the spectral components of laser sources. For instance, exploiting complex structured light beams [39][40][41] enabled by properly designed metasurfaces, a superposition of multiple OAM states could be realized, which may provide a novel route for the generation of laser frequency combs featuring a tailorable spacing between their spectral lines.…”

The Rotational Doppler Effect of Twisted Photons in Scattered Fields

“…When the scattering surface has a transverse velocity that can be split into a uniform angular velocity Ω and a constant radial velocity v r in Figure S1b (Supporting Information), each mode ( n , l ) has a transverse Doppler frequency shift Δ f ⊥ ( l , n ) = l Ω/(2π)+ nv r / T . There are two terms, the rotational Doppler frequency shift term and the radial Doppler frequency shift, [ 58 ] associated with the mode indices l and n of the scattered light field, respectively (see Note S2 in the Supporting Information in detail).…”