Spin-orbit interaction of light induced by transverse spin angular momentum engineering

Author(s):

Zengkai Shao and Jiangbo Zhu and Yujie Chen and Yanfeng Zhang and Siyuan Yu

Abstract:

“The investigations on optical angular momenta and their interactions have broadened our knowledge of light’s behavior at sub-wavelength scales. Recent studies further unveil the extraordinary characteristics of transverse spin angular momentum in confined light fields and orbital angular momentum in optical vortices. Here we demonstrate a direct interaction between these two intrinsic quantities of light. By engineering the transverse spin in the evanescent wave of a whispering-gallery-mode-based optical vortex emitter, a spin-orbit interaction is observed in generated vortex beams. Inversely, this unconventional spin-orbit interplay further gives rise to an enhanced spin-direction locking effect in which waveguide modes are unidirectionally excited, with the directionality jointly controlled by the spin and orbital angular momenta states of light. The identification of this previously unknown pathway between the polarization and spatial degrees of freedom of light enriches the spin-orbit interaction phenomena, and can enable various functionalities in applications such as communications and quantum information processing.”

Link to Publications Page

Publication: Nature Communications

Issue/Year/DOI: Nature Communicationsvolume 9, Article number: 926 (2018)
DOI: 10.1038/s41467-018-03237-5

Single-shot measurement of the orbital-angular-momentum spectrum of light.

Author(s):

Kulkarni, Girish and Sahu, Rishabh and Magaña-Loaiza, Omar S. and Boyd, Robert W. and Jha, Anand K.

Abstract:

“The existing methods for measuring the orbital-angular-momentum (OAM) spectrum suffer from issues such as poor efficiency, strict interferometric stability requirements, and too much loss. Furthermore, most techniques inevitably discard part of the field and measure only a post-selected portion of the true spectrum. Here, we propose and demonstrate an interferometric technique for measuring the true OAM spectrum of optical fields in a single-shot manner. Our technique directly encodes the OAM-spectrum information in the azimuthal intensity profile of the output interferogram. In the absence of noise, the spectrum can be fully decoded using a single acquisition of the output interferogram, and, in the presence of noise, acquisition of two suitable interferograms is sufficient for the purpose. As an important application of our technique, we demonstrate measurements of the angular Schmidt spectrum of the entangled photons produced by parametric down-conversion and report a broad spectrum with the angular Schmidt number 82.1.”

Link to Publications Page

Publication: Nature Communications

Issue/Year/DOI: Nature Communicationsvolume 8, Article number: 1054 (2017)
DOI: 10.1038/s41467-017-01215-x

Plasmonic computing of spatial differentiation.

Author(s):

Zhu, Tengfeng and Zhou, Yihan and Lou, Yijie and Ye, Hui and Qiu, Min and Ruan, Zhichao and Fan, Shanhui

Abstract:

“Optical analog computing offers high-throughput low-power-consumption operation for specialized computational tasks. Traditionally, optical analog computing in the spatial domain uses a bulky system of lenses and filters. Recent developments in metamaterials enable the miniaturization of such computing elements down to a subwavelength scale. However, the required metamaterial consists of a complex array of meta-atoms, and direct demonstration of image processing is challenging. Here, we show that the interference effects associated with surface plasmon excitations at a single metal-dielectric interface can perform spatial differentiation. And we experimentally demonstrate edge detection of an image without any Fourier lens. This work points to a simple yet powerful mechanism for optical analog computing at the nanoscale.”

Link to Publications Page

Publication: Nature Communications

Issue/Year/DOI: Nature Communications volume 8, Article number: 15391 (2017)
DOI: 10.1038/ncomms15391

Direct measurement of a 27-dimensional orbital-angular-momentum state vector

Author(s):

Malik, Mehul and Mirhosseini, Mohammad and Lavery, Martin P. J. and Leach, Jonathan and Padgett, Miles J. and Boyd, Robert W.

Abstract:

“The measurement of a quantum state poses a unique challenge for experimentalists. Recently, the technique of ‘direct measurement’ was proposed for characterizing a quantum state in situ through sequential weak and strong measurements. While this method has been used for measuring polarization states, its real potential lies in the measurement of states with a large dimensionality. Here we show the practical direct measurement of a high-dimensional state vector in the discrete basis of orbital angular momentum. Through weak measurements of orbital angular momentum and strong measurements of angular position, we measure the complex probability amplitudes of a pure state with a dimensionality, d=27. Further, we use our method to directly observe the relationship between rotations of a state vector and the relative phase between its orbital-angular-momentum components. Our technique has important applications in high-dimensional classical and quantum information systems and can be extended to characterize other types of large quantum states.”

Link to Publications Page

Publication: Nature Communications

Issue/Year/DOI: Nature Communications volume 5, Article number: 3115 (2014)
DOI: 10.1038/ncomms4115