Valley-contrasting Physics in All-dielectric Photonic Crystals
Author
Bendtsen, Reiko Inoue
Term
4. term (FYS10)
Education
Publication year
2022
Pages
105
Abstract
This thesis surveys two-dimensional photonic topological insulators with a focus on valley photonic crystals in all-dielectric platforms and numerically explores valley-contrasting physics. Using plane-wave expansion, fast FFT-based iterative solvers, and a Green’s Function Area Integral Equation Method, we compute band structures, Berry curvature and valley Chern numbers, and model domain-wall interfaces between topologically distinct, finite photonic crystals. Simulations show kink states that guide light robustly with minimal backscattering even through sharp Z-shaped bends—behavior not available in conventional photonic-crystal waveguides. Comparing several interface terminations, we find that bearded-stack domain walls yield the most robust propagation among the cases studied. We also investigate coupling from a chiral light source, confirming unidirectional excitation of valley-chiral states at bearded-stack walls, governed by the dot product (coupling) between the fields and the chiral dipole moment. The work clarifies design principles for valley-PTI waveguides and highlights their potential for robust routing and chiral light–matter interfaces in all-dielectric photonics.
Dette speciale giver et overblik over todimensionelle fotoniske topologiske isolatorer med fokus på dal-fotoniske krystaller i helt dielektriske platforme og undersøger numerisk dal-kontrasterende fysik. Ved hjælp af planbølge-ekspansion, hurtige FFT-baserede iterative metoder og en Green’s Function Area Integral Equation-metode beregner vi båndstrukturer, Berry-krumning og dal-Chern-tal og modellerer domænevægge mellem topologisk forskellige, endelige fotoniske krystaller. Simulationerne viser kink-tilstande, der leder lys robust med minimal bagspredning selv gennem skarpe Z-formede bøjninger—en adfærd der ikke findes i konventionelle fotoniske krystalbølgeleder. Ved at sammenligne flere grænsefladekonfigurationer finder vi, at bearded-stack-domænevægge giver den mest robuste udbredelse blandt de undersøgte tilfælde. Vi undersøger også kobling fra en chiral lyskilde og bekræfter ensrettet excitation af dal-chirale tilstande ved bearded-stack-vægge, styret af skalarproduktet (koblingen) mellem feltet og den chirale dipolmoment. Arbejdet tydeliggør designprincipper for dal-PTI-bølgeleder og peger på potentialet for robuste rute- og chiral-lysstof-grænseflader i helt dielektrisk fotonik.
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