Anomalous zero-group-velocity photonic bonding states with local chirality

Abstract

Chirality is a crucial property to enthrone quantum computation on-chip and thereby engineer efficient deterministic photonic building blocks analogous to gates and transistors. Photonic Crystal Waveguides (PCWs) are promising for this purpose due to circular polarisation points that can unbalance the directionality of a quantum emitter (QE). In non-symmorphic waveguides, the local chirality is prominent and extends into high field intensity regions. Nevertheless, the Purcell effect at circular polarisation points saturates near the band-edge, the preferred region for Quantum ElectroDynamics (QED). Consequently, uni-directionality and ultra-strong light-matter interaction are difficult to combine. Here, we detract from the vicinity of the band-edge, and couple modes with different parities by breaking the mirror symmetry. Simulated bandstructures of the implemented Photonic Bonding States (PBS) display single-mode anomalous zero-group-velocity (ZGV) points with a non-vanishing energy flow far from the band edge, synonymous with an idealistic infinite Purcell Factor. Fabricated devices in Silicon (Si) slabs demonstrate an extremely large slow-down effect. On top of that, their simulated electric field patterns feature circular polarisation points at high field intensity regions where a QE would acquire uni-directional emission behaviour. This method to engineer PBS in PCWs paves the way for outperforming chiral light-matter experiment on-chip.

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ORCID for Shinichi Saito: orcid.org/0000-0003-1539-1182

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