Exploring the Optical Bound State in the Continuum in a Dielectric Grating Coupled Plasmonic Hybrid System

Abstract

the hybridized modes arising from the coupling of photonic and plasmonic resonances have been investigated widely. [7] The hybridized modes realized in diverse configurations using defect modes, [8] plasmonic nano-cavities, [9] Fabry-Perot metallic trench resonator, [10] etc., successfully demonstrate improved outcomes in terms of sensitivity, figure of merit, confinement, and lightmatter interaction. [11] Very recently, it has been noticed that the interaction of two different optical channels leads to the formation of a bound state in the continuum (BIC) and a resultant quasi-BIC hybrid mode. [12] The BIC is considered as a confined state in an open system with an infinite quality factor (Q-factor), which can extensively interact with the radiation channel. [13] Although the concept of BIC was proposed by von Neumann and Wigner in 1921, [14] the experimental observation of its existence is manifested only in the last decades. [15,16] Nevertheless, a true BIC is a mathematical perception that one can never achieve with either quantum or classical systems using physical parameters. [16] Fundamentally, the BICs can be of two kinds; the symmetry protected BIC (SP-BIC) [4,17,18] and the accidental BICs. [19] The SP-BICs are the inherent nature of a wave system; they are the discrete modes in the Brillouin zone near the gamma (Γ) point and are not allowed to interact with the free space radiation due to its symmetry incompatibilities. [17] Conversely, the accidental BICs are the consequence of the interference phenomena. For a system with two different resonance phenomena continuously changing with the parametric variation, at one particular set of parameters, there may occur an avoided crossing through which both the modes can interact and interfere destructively, resulting in the vanishing of one of the modes with an infinite quality factor. [19] Such an accidental vanishing of modes is explained by the Friedrich-Wintgen scenario. [20] The SP-BIC can be accessed by symmetry breaking structure [21] or by oblique illumination, resulting in the generation of resonant modes with a huge Q-factor called the quasi-BIC. [22] Although a true BIC mode is a dark mode with infinite lifetime and zero line width, in reality, the Q-factor of the BIC is finite because of restricted dimension, losses, and imperfection in the fabricated system. Thus, only the quasi-BICs with finite spectral width and Q-factor can be realized experimentally. The quasi-BIC has been explored for numerous applications including compact photonic chip for communication, [23] extreme narrowband transmission spectrum, [4] lasing, [24] The bound state in the continuum (BIC) explores the extraordinary optical properties of a system possessing wave characteristics that gained recent importance for practical applications, including lasing, sensing, optical tweezing, nonlinear interactions, and many more. Unlike a pure optical or plasmonic system, a hybrid architecture with coupled photonicplasmonic characteristics can offer the intermittent resonant modes for s...

Analogue of Electromagnetically Induced Transparency in an All-Dielectric Double-Layer Metasurface Based on Bound States in the Continuum

“…In fact, due to the finite extent of structures, material absorption and other external disturbances, ideal (or dark) BICs collapse to a Fano resonance with a finite Q factor, which is called quasi-BIC [20]. At present, a large number of Fano resonances with high Q factors have been obtained through quasi-BIC in the fields of photonic crystals [21][22][23][24], gratings [25,26], waveguides [27] and MMs [28,29]. There are three main types of BIC in MMs: symmetrically protected BICs (S-P BICs) [28][29][30][31][32][33][34], Friedrich-Wintgen BICs (F-W BICs) [35][36][37][38][39] and topologically protected BICs (T-P BICs) [40].…”

Catalytic Metasurfaces Empowered by Bound States in the Continuum

“…All-dielectric metasurfaces underpinned by the physics of bound states in the continuum (BIC) have seen surging interest due to their spectral selectivity, strong light confinement, and giant enhancement of electromagnetic fields, − sparking applications in diverse fields including nanoscale lasing, − biomolecular sensing, − and nonlinear photonics. − However, to the best of our knowledge, BICs have not yet been tailored for photocatalytic applications. Conceptually, a BIC is a localized state existing at the same energy level as a continuum of radiation modes .…”

Fabrication of lithium niobate metasurfaces via a combination of FIB and ICP-RIE

“…Such nano-grating structures could support the bound states in the continuum (BIC) mode when the incident is polarized along the ridge orientation [42] . The BIC modes represent the confined states in an open system with an infinite Q-factor that cannot interact extensively with radiation channels owing to symmetry incompatibility [43] . Fundamentally, symmetry protected BIC (SP-BIC) is the inherent property of a wave system, and the discrete mode in the Brillouin zone near the Γ point.…”