Abstract
Orbital angular momentum (OAM) of optical vortex beams has been regarded as an independent physical dimension of light with predominant information-carrying potential. However, the presence of scattering environment and turbulent atmosphere scrambles the helical wavefront and destroys the orthogonality of modes in vortex beam propagation. Here, we propose and experimentally demonstrate a new basis for the recovery of the OAM mode using a holographic ghost diffraction scheme. The technique utilizes the speckle field generated from a rotating diffuser for optical vortex mode encoding, and the fourth-order correlation of the speckle field for the efficient recovery of the associated modes. Furthermore, we successfully demonstrate the complex-field recovery of OAM modes by the adoption of a holography scheme in combination with the ghost diffraction system. We evaluate the feasibility of the approach by simulation and followed by experimental demonstration for the recovery of various sequentially encoded OAM modes. Finally, the efficacy of the recovered modes was quantitatively analyzed by an OAM mode analysis utilizing orthogonal projection scheme.
Highlights
Optical beams with helical wavefronts and associated orbital angular momentum (OAM) have become a focus of intense research in recent years owing to its high-capacity information bearing characteristics with noteworthy applications in various domains of imaging and communication [1]
The correlation hologram preserves the signature of the vortex mode in the intensity cross-correlation function, which can be clearly seen as the generation of the fork pattern corresponding to different topological values in a way analogous to the fork hologram in conventional off-axis holography
The amplitude and phase distributions of the OAM modes are retrieved from the correlation hologram by utilizing the Fourier domain filtering approach [38], and the corresponding results are shown in Figure 4e–h and Figure 4i–l, respectively
Summary
Optical beams with helical wavefronts and associated orbital angular momentum (OAM) have become a focus of intense research in recent years owing to its high-capacity information bearing characteristics with noteworthy applications in various domains of imaging and communication [1]. Following theoretical investigations on the properties of optical vortex beams, several experimental techniques were realized for the generation of helically phased beams by utilizing spiral phase plate (SPP), diffractive optical elements, cylindrical lens with mode converters, q-plates, meta surface, etc. Recent years have witnessed the extension of the regime of optical vortices from coherent light to low coherent light with the demonstration of helicoidal modes in partially coherent beams [6,7,8]. Experimental strategies to generate vortices in coherence function by utilizing the partially coherent light arrays were demonstrated by the controlled modulation in the correlation structure of the light fields [13,14]
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