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Register a new userBroadband Optical Fully Differential Operation Based on the Spin-orbit Interaction of Light
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Optical technology may provide important architectures for future computing, such as analog optical computing and image processing. Compared with traditional electric operation, optical operation has shown some unique advantages including faster operating speeds and lower power consumption. Here, we propose an optical full differentiator based on the spin-orbit interaction of light at a simple optical interface. The broadband optical operation is independent on the wavelength due to the nature of purely geometric. As an important application of the fully differential operation, the broadband image processing of edge detection is demonstrated. By adjusting the polarization of the incident beam, the one-dimension edge imaging at any desirable direction can be obtained. The broadband image processing of edge detection provides possible applications in autonomous driving, target recognition, microscopic imaging, and augmented reality.
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The photonic spin Hall effect (SHE) can be regarded as a direct optical analogy of the SHE in electronic systems where a refractive index gradient plays the role of electric potential. However, it has been demonstrated that the effective refractive index fails to adequately explain the lightmatter interaction in atomically thin crystals. In this paper, we examine the spin-orbit interaction on the surface of the freestanding atomically thin crystals. We find that it is not necessary to involve the effective refractive index to describe the spin-orbit interaction and the photonic SHE in the atomically thin crystals. The strong spin-orbit interaction and giant photonic SHE have been predicted, which can be explained as the large polarization rotation of plane-wave components in order to satisfy the transversality of photon.
We develop a novel theoretical framework describing polariton-enhanced spin-orbit interaction of light on the surface of two-dimensional media. Starting from the integral formulation of electromagnetic scattering, we exploit the reduced dimensionality of the system to introduce a quantum-like formalism particularly suitable to fully take advantage of rotational invariance. Our description is closely related to that of a fictitious spin one quantum particle living in the atomically thin medium, whose orbital, spin and total angular momenta play a key role in the scattering process. Conservation of total angular momentum upon scattering enables to physically unveil the interaction between radiation and the two-dimensional material along with the detailed exchange processes among orbital and spin components. In addition, we specialize our model to doped extended graphene, finding such spin-orbit interaction to be dramatically enhanced by the excitation of surface plasmon polaritons propagating radially along the graphene sheet. We provide several examples of the enormous possibilities offered by plasmon-enhanced spin-orbit interaction of light including vortex generation, mixing, and engineering of tunable deep subwavelength arrays of optical traps in the near field. Our results hold great potential for the development of nano-scaled quantum active elements and logic gates for the manipulation of hyper-entangled photon states as well as for the design of artificial media imprinted by engineered photonic lattices tweezing cold atoms into the desired patterns.
The edge diffraction of a homogeneously polarized light beam is studied theoretically based on the paraxial optics and Fresnel-Kirchhoff approximation, and the dependence of the diffracted beam pattern of the incident beam polarization is predicted. If the incident beam is circularly polarized, the trajectory of the diffracted beam centre of gravity experiences a small angular deviation from the geometrically expected direction. The deviation is parallel to the screen edge and reverses the sign with the polarization handedness; it is explicitly calculated for the case of a Gaussian incident beam with plane wavefront. This effect is a manifestation of the spin-orbit interaction of light and can be interpreted as a revelation of the internal spin energy flow immanent in circularly polarized beams. It also exposes the vortex character of the weak longitudinal field component associated with the circularly polarized incident beam.
The ability to create dynamic, tailored optical potentials has become important across fields ranging from biology to quantum science. We demonstrate a method for the creation of arbitrary optical tweezer potentials using the broadband spectral profile of a superluminescent diode combined with the chromatic aberration of a lens. A tunable filter, typically used for ultra-fast laser pulse shaping, allows us to manipulate the broad spectral profile and therefore the optical tweezer potentials formed by focusing of this light. We characterize these potentials by measuring the Brownian motion of levitated nanoparticles in vacuum and, also demonstrate interferometric detection and feedback cooling of the particle,s motion. This simple and cost-effective technique will enable a wide range of applications and allow rapid modulation of the optical potential landscape in excess of MHz frequencies.
Optical waveguides in the form of glass fibers are the backbone of global telecommunication networks. In such optical fibers, the light is guided over long distances by continuous total internal reflection which occurs at the interface between the fiber core with a higher refractive index and the lower index cladding. Although this mechanism ensures that no light escapes from the waveguide, it gives rise to an evanescent field in the cladding. While this field is protected from interacting with the environment in standard optical fibers, it is routinely employed in air- or vacuum-clad fibers in order to efficiently couple light fields to optical components or emitters using, e.g., tapered optical fiber couplers. Remarkably, the strong confinement imposed by the latter can lead to significant coupling of the lights spin and orbital angular momentum. Taking advantage of this effect, we demonstrate the controlled directional spontaneous emission of light by quantum emitters into a sub-wavelength-diameter waveguide. The effect is investigated in a paradigmatic setting, comprising cesium atoms which are located in the vicinity of a vacuum-clad silica nanofiber. We experimentally observe an asymmetry higher than 10:1 in the emission rates into the counterpropagating fundamental guided modes of the nanofiber. Moreover, we demonstrate that this asymmetry can be tailored by state preparation and suitable excitation of the quantum emitters. We expect our results to have important implications for research in nanophotonics and quantum optics and for implementations of integrated optical signal processing in the classical as well as in the quantum regime.
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