Optically Reconfigurable Spin-Valley Hall Effect of Light in Coupled Nonlinear Ring Resonator Lattice

Abstract

Scattering immune propagation of light in topological photonic systems may revolutionarize the design of integrated photonic circuits for information processing and communications. In optics, various photonic topological circuits have been developed, which were based on classical emulation of either quantum spin Hall effect or quantum valley Hall effect. On the other hand, the combination of both the valley and spin degrees of freedom can lead to a new kind of topological transport phenomenon, dubbed quantum spin valley Hall effect (QSVH), which can further expand the number of topologically protected edge channels and would be useful for information multiplexing. However, it is challenging to realize QSVH in most known material platforms, due to the requirement of breaking both the (pseudo-)fermionic time-reversal ( ) and parity symmetries ( ) individually, but leaving the combined symmetry  intact. Here, we propose an experimentally feasible platform to realize QSVH for light, based on coupled ring resonators mediated by optical Kerr nonlinearity. Thanks to the inherent flexibility of cross-mode modulation (XMM), the coupling between the probe light can be engineered in a controllable way such that spin-dependent staggered sublattice potential emerges in the effective Hamiltonian. With delicate yet experimentally feasible pump conditions, we show the existence of spin valley Hall induced topological edge states. We further demonstrate that both degrees of freedom, i.e., spin and valley, can be manipulated simultaneously in a reconfigurable manner to realize spin-valley photonics, doubling the degrees of freedom for enhancing the information capacity in optical communication systems.

1D Photonic Topological Insulators Composed of Split Ring Resonators: A Mini Review

“…[184,185] Recently, the hybrid spin-valley Hall effect and the spin-valley coupled-edge states have also been demonstrated. [186][187][188][189][190] Overall, the charming topological properties of the quantum valley Hall phase have opened up novel capabilities to construct robust photonic devices, including waveguides, [191,192] delay lines, [193,194] lasers, [195,196] beam splitters, [197] and wireless communications. [198]…”

Isotacticity in chiral phononic crystals for low-frequency bandgap

“…The bandgap in phononic crystals provides a new path to high device performance in vibration isolation [1,2], thermal insulation [3,4], and robust topological wave transmission [5,6]. In terms of the low-frequency and broadband isolation for elastic waves, the great efforts inspired by Bragg scattering [7] and local resonance [8] have been done, such as rainbow trapping [9][10][11], gradient distribution [11][12][13][14][15], coupled Bragg scattering and local resonance [16][17][18][19], acoustic black holes [20,21], or nonlinear local resonance [22][23][24][25]. Even, the quasi zero stiffness, another one of appealing strategies, might be a solution of this dilemma because it can lower the frequency of the Bragg scattering bandgap [26][27][28], nevertheless the robustness and stability of the system is debatable when the metastructures are at the quasi-zero state.…”

Description of bandgaps opening in chiral phononic crystals by analogy with Thomson scattering

“…The remarkable feature, i.e. the bandgap, provides a powerful ability to control the wave propagation, such as the design of the non-reciprocal device [4][5][6] and the recent valley state formation with Dirac points degeneracy operation in its bandgap [7,8].…”