摘要: Enhancement of light-matter interactions is of great importance for many
nanophotonic devices, and one way to achieve it is to feed energy perfectly to
the strongly coupled system. Here, we propose gap-perturbed dimerized gratings
based on bulk WS2 for flexible control of the strong coupling between
quasi-bound state in the continuum (quasi-BIC) and exciton. The simulation
results show that when a gap perturbation is introduced into the system
resulting in the Brillouin zone folding, BIC transforms into quasi-BIC whose
quality factor (Q-factor) is related to the value of gap perturbation. The
strong coupling results in the anti-crossover behavior of the absorption
spectra, and thus a Rabi splitting energy of 0.235 eV is obtained. Temporal
coupled-mode theory is employed to analyze the strong coupling system, and the
absorption of the system could be enhanced, by modulating the damping rate of
quasi-BIC to make the system satisfy the strong critical coupling condition.
Furthermore, polaritonic coherent perfect absorption is achieved by using the
two-port source excitation. This work could provide ideas for enhancing
light-matter interactions and a promising prospect for polariton-based
light-emitting or lasing devices.