Investigating exceptional points in dark-bright mode-coupled plasmonic systems.

Area of Science:

• Optics and Photonics
• Quantum Mechanics
• Materials Science

Background:

• Exceptional points (EPs) in non-Hermitian systems are vital for applications like unidirectional transmitters and sensors.
• Theoretical understanding of EPs in reflection, transmission, and absorption spectra remains limited.
• Plasmonic systems offer a platform for investigating complex optical phenomena.

Purpose of the Study:

• To numerically investigate the variations of EPs in reflection, transmission, and absorption spectra within dark-bright mode-coupled plasmonic systems.
• To propose and verify a theoretical assumption relating EPs to spectral properties using representation transformation theory.
• To establish guiding principles for designing micro- and nano-photonic devices based on EP behavior.

Main Methods:

• Temporal coupled-mode theory was employed for numerical investigations.
• Representation transformation theory was used to develop theoretical assumptions.
• Two metasurfaces were designed and simulated to validate the theoretical findings.

Main Results:

• The intermediate representation (IR) was linked to the reflection spectrum, and the normal representation (NR) to the absorption spectrum.
• Modified formulas were derived for spectral behavior near EPs.
• Absorption loss of the dark mode linearly correlates with EPs across reflection, transmission, and absorption spectra.
• Radiation loss of the bright mode shows a linear relationship only with absorption spectrum EPs.

Conclusions:

• The study provides a theoretical framework and experimental validation for understanding EPs in coupled plasmonic systems.
• Established relationships between spectral losses and EPs offer a method to manipulate spectral line splitting.
• Findings guide the design of advanced micro- and nano-photonic devices by controlling optical losses and coupling coefficients.