Helical transport in coupled resonator waveguides

Abstract

We show that a synthetic pseudospin-momentum coupling can be used to design quasi-onedimensional disorder-resistant coupled resonator optical waveguides (CROW). In this structure, the propagating Bloch waves exhibit a pseudospin-momentum locking at specific momenta where backscattering is suppressed. We quantify this resistance to disorder using two methods. First, we calculate the Anderson localization length ξ, obtaining an order of magnitude enhancement compared to a conventional CROW for typical device parameters. Second, we study propagation in the time domain, finding that the loss of wavepacket purity in the presence of disorder rapidly saturates, indicating the preservation of phase information before the onset of Anderson localization. Our approach of directly optimizing the bulk Bloch waves is a promising alternative to disorder-robust transport based on higher dimensional topological edge states. arXiv:1902.06697v3 [physics.optics]

Topological phases in ring resonators: recent progress and future prospects

“…Zhu et al [73] have proposed a honeycomb lattice design hosting topological edge states which coexist with a nearly flat bulk band. It is also possible to shrink these two-dimensional lattices down to quasi-one-dimensional delay lines, which maintain some resistance against disorder [74].…”

Disorder-protected quantum state transmission through helical coupled-resonator waveguides

“…The tight-binding Hamiltonian governing time evolution of one specific circulation direction (counter-clockwise) in the absence of disorder reads [23,24,32,35],…”

“…where J is the hopping strength and field operators ân , bn represent the annihilation operators at the sites in the nth unit cell, while their conjugates are associated with the corresponding creation operators. The complex hopping terms arise due to the specially introduced asymmetry of the link rings [32]. Note that we measure frequencies with respect to a resonance of a single isolated ring, such that the eigenvalues of Ĥ0,ccw are modal frequency detunings with respect to this resonance.…”

“…Recently, we proposed a model of a quasi-1D coupled-resonator optical waveguide (CROW) exhibiting a similar helical spin-momentum locked dispersion (H-CROW), by combining circulation direction and sublattice spin-like degrees of freedom. The former effectively breaks time-reversal symmetry, while the coupling between different sublattices can be tuned to create a sublatticemomentum locked dispersion relation [32]. This results in a suppression of backscattering and enhancement of localization length compared to the regular CROW model, as well as preservation of phase information.…”

Topological phases in ring resonators: recent progress and future prospects

“…Zhu et al have proposed a honeycomb lattice design hosting topological edge states which co-exist with a nearly flat bulk band 62 . It is also possible to shrink these twodimensional lattices down to quasi-one-dimensional delay lines, which maintain some resistance against disorder 63 .…”