article · Physical Review Applied
This research explores Friedrich-Wintgen bound states in the continuum within a photonic and plasmonic T-shaped cavity. Such states trap light within open structures to generate high-quality-factor resonances. By studying a cavity formed by two horizontal guides connected to a vertical stub, the investigation proves that making the horizontal guide lengths commensurate is the necessary condition to produce these states. When this condition is met, the electric field vanishes at the junction, isolating the mode from the stub and attached waveguides. Introducing slight deviations transforms these bound states into sharp resonance phenomena, including electromagnetically induced transparency and Autler-Townes splitting. Theoretical models using Green's function were confirmed through radiofrequency experiments with coaxial cables and infrared simulations in metal-insulator-metal plasmonic waveguides.
Controlling how light is trapped and transmitted in open microscopic structures is essential for creating compact optical devices. By demonstrating how simple geometric adjustments can produce sharp optical resonances, this work provides a clearer mechanism for designing components that route, filter, or detect light efficiently in integrated photonic and plasmonic systems.
The findings point towards applications in optical filtering and high-sensitivity, on-chip refractive index sensing for photonic platforms. The work represents early-stage experimental and simulation research, validated in radiofrequency laboratory setups and infrared waveguide models. Commercial developers of optical sensors and integrated photonic circuits could eventually adapt these cavity geometries, though practical deployment will require further fabrication and testing at operational nanoscale optical frequencies.
AI-generated from the published abstract. Always read the original work before citing.
Bound states in the continuum (BICs) in open cavities have attracted considerable attention in wave physics due to their ability to confine light and produce high-quality-factor resonances with promising applications for filtering and sensing. One of the most interesting types of BICs is Friedrich-Wintgen (FW) BICs, which result from destructive interference of two interacting modes belonging to the same radiation channel. Here, we investigate theoretically and experimentally FW BICs in a photonic and plasmonic T-shaped cavity made of two horizontal guides of lengths ${d}_{2}$ and ${d}_{3}$ coupled to a vertical stub of length ${d}_{1}$. We demonstrate that the necessary condition for obtaining BICs consists in taking the lengths of the two horizontal guides ${d}_{2}$ and ${d}_{3}$ commensurate. This BIC is a common mode of the guides of lengths ${d}_{2}$ and ${d}_{3}$, such as the electric field vanishes at their connection point with the stub of length ${d}_{1}$; this BIC is independent of ${d}_{1}$ and the infinite waveguide to which the whole cavity will be attached. We show that, depending on ${d}_{1}$, the FW BIC appears as the consequence of the interaction between two eigenmodes of the originally isolated cavity where the width of one mode vanishes giving rise to FW BIC, while the width of the second mode becomes broad. In addition, we show that by slightly deviating from the BIC condition, the latter transforms to either electromagnetically induced transparency (EIT) or reflection or Autler-Townes splitting (ATS) resonances. Both EIT and ATS effects are qualified as a transparency window between two transmission zeros, but with different physical origins. We exploit the Akaike's information criterion test to discern EIT from ATS and distinguish the regime where the EIT or ATS effect dominates. The theoretical results, obtained by means of the Green's function method, are validated both by experimental measurements using coaxial cables in the radiofrequency domain and numerical simulations using metal-insulator-metal plasmonic waveguides operating in the infrared domain. The sensitivity of the PIT (the plasmonic analogue of EIT) resonances to the dielectric inside the waveguides can be used to design a highly sensitive sensor, which makes it suitable for an on-chip optical sensing platform.
This page summarises published work. The authoritative version sits with the publisher.
DOI: 10.1103/physrevapplied.20.044015
Is something wrong with this record? Report it or request removal.
Discussion
Have you built on this work, tried to replicate it, or seen it applied in practice? Share what you know. Verified researchers and MARATTO™ domain experts can open a discussion, and any member can reply. Contributions are reviewed before they appear.
No discussion yet. Open the first thread.
New to MARATTO™? Create a free account.
