Conservation of orbital angular momentum in air core optical fibers

By P. Gregg, Poul Kristensen, S. Ramachandran. 2014

271 citations recorded by the source corpus.

Light's orbital angular momentum (OAM) is a conserved quantity in cylindrically symmetric media; however, it is easily destroyed by free-space turbulence or fiber bends, because anisotropic perturbations impart angular momentum. We observe the conservation of OAM even in the presence of strong bend perturbations, with fibers featuring air cores that appropriately sculpt the modal density of states. In analogy to the classical reasoning for the enhanced stability of spinning tops with increasing angular velocity, these states' lifetimes with OAM magnitude. Consequently, contrary to convention wisdom that ground states of systems are the most stable, OAM longevity in air-core fiber increases with mode order. Aided by conservation of this fundamental quantity, we demonstrate fiber propagation of 12 distinct higher-order OAM modes, of which 8 remain low-loss and >98% pure from near-degenerate coupling after km-length propagation. The first realization of long-lived higher-order OAM states, thus far posited to exist primarily in vacuum, is a necessary condition for achieving the promise of higher-dimensional OAM-based classical and quantum communications over practical distances.

Subfields: Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/1f31909226e5ac540f094d8295a0623f68e49c15

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In Atomic and Molecular Physics, and Optics

In Electrical and Electronic Engineering

Citations in the corpus

Orbital Angular Momentum States Enabling Fiber-based High-dimensional Quantum Communication (2018, background): “[44] P.”
Advances in communications using optical vortices (2016, background): “, negligible mode cross talk), such as inverse-parabolic gradedindex fiber [83].”
Twisted photons: new quantum perspectives in high dimensions (2017, unknown): “Moreover, high-dimensional transmission is not possible, but two other approaches are conceivable: One approach would be carefully designing OAM multimode fibers, in which the modes are degenerate but do not couple to each other [118].”
Optical communications using orbital angular momentum beams (2015, background): “A recently reported air-core fiber has been demonstrated to further increase the refractive index difference of eigenmodes such that the fiber is able to stably transmit 12 OAM states (l 5, 6, and 7, each with two orthogonal polarizations) over 10 m, of which eight of these states remained low loss ”