Photonic bound states in the continuum in nanostructured transition metal dichalcogenides for strong photon–exciton coupling

Abstract

Optical cavities supporting the optical bound states in the continuum (BICs) with infinite radiative lifetime have recently been widely reported. Here, we theoretically investigate BICs in an ultrathin photonic structure consisting of a multilayer, nanostructured transition metal dichalcogenide (TMD). Using finite element simulations, we demonstrate two distinct groups of BICs, namely symmetry-protected BICs and interference-based BICs, in the photonic system. Under normal incidence, their dispersion can be mediated by altering the grating pitch, which makes it possible to explore the strong coupling of these two photonic modes with the TMD exciton band in the same structure. This work expands not only the library of traditional nanophotonic approaches, but also provides more possibilities for optoelectronic devices toward miniaturization.

Strong coupling of excitons in patterned few-layer WS2 with guided mode and bound state in the continuum

“…The refractive index of the dielectric substrate is n s = 1.45. Here, the permittivity of bulk WS 2 is employed as the permittivity of the few-layer WS 2 , which is described as: 48 e…”

“…The refractive index of the dielectric substrate is n s = 1.45. Here, the permittivity of bulk WS 2 is employed as the permittivity of the few-layer WS 2 , which is described as: 48 where ε 0 = 20.25 stands for the background permittivity, E ex = 2 eV denotes the exciton energy, f os = 0.2 is the oscillator strength, and Γ ex = 0.05 eV denotes the full linewidth. 48 The real component and imaginary component of the permittivity of the WS 2 film calculated according to eqn (1) are plotted in Fig.…”

“…Here, the permittivity of bulk WS 2 is employed as the permittivity of the few-layer WS 2 , which is described as: 48 where ε 0 = 20.25 stands for the background permittivity, E ex = 2 eV denotes the exciton energy, f os = 0.2 is the oscillator strength, and Γ ex = 0.05 eV denotes the full linewidth. 48 The real component and imaginary component of the permittivity of the WS 2 film calculated according to eqn (1) are plotted in Fig. 1(c) and (d), respectively.…”

“…[45][46][47] Zong et al proposed a structure with WS 2 grating of 10 nm thickness atop a dielectric substrate, where the maximum Rabi splitting could be enhanced up to 120 meV. 48 Here, the strong coupling of excitons in few-layer WS 2 with GMR and BIC is investigated and compared. First, a GMR structure and a BIC structure are designed and the physical origin is investigated and verified.…”

“…45–47 Zong et al proposed a structure with WS 2 grating of 10 nm thickness atop a dielectric substrate, where the maximum Rabi splitting could be enhanced up to 120 meV. 48…”