研究目的
Investigating the polarization-based branch selection of bound states in the continuum in dielectric waveguide modes anti-crossed by a metal grating.
研究成果
The study demonstrates that the branch on which the FW-BIC appears in the anti-crossing dispersion of a photonic system can be selected by the incident polarization. This mechanism is explained by TCMT in terms of the polarization-dependent phase relation between the relevant waveguide modes forming the BIC. The findings suggest the potential for external controllability of BICs in various optical and photonic devices, although the role of plasmonic effects in the observed phenomena remains an open question.
研究不足
The study's findings are specific to the described dielectric waveguide structure with a metal grating. The applicability to other structures or materials is not explored. Additionally, the theoretical analysis assumes lossless conditions for clarity, which may not fully represent practical scenarios with material losses.
1：Experimental Design and Method Selection:
The study employs a planar dielectric waveguide structure with a gold grating on a dielectric layer and a back layer of metal. The investigation focuses on the appearance of BICs near the anti-crossing point of dispersion curves, using temporal coupled mode theory (TCMT) and spatial coupled mode theory (SCMT) for analysis.
2：Sample Selection and Data Sources:
The structure consists of a gold grating on a dielectric layer with a backing metal layer of infinite thickness. The relectance and fields inside the device were calculated by SCMT for incident plane waves with S or P polarization.
3：List of Experimental Equipment and Materials:
A gold grating on a dielectric layer with a back layer of metal. The gold grating's permittivity is modeled using a Drude–Lorentz model fitted to Johnson–Christy data.
4：Experimental Procedures and Operational Workflow:
The study involves numerical calculations of the electric fields inside the dielectric layer using SCMT, followed by analysis using TCMT to understand the BIC formation mechanism.
5：Data Analysis Methods:
The phase difference between waveguide modes is evaluated to determine the sign of the product of coupling coefficients, which influences the BIC branch selection.
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