Active control of an electromagnetically induced transparency analogue in a coupled dual bound states in the continuum system integrated with graphene.

Abstract

Electronically induced transparency (EIT) is a coherent optical phenomenon that induces interference within atoms, allowing certain specific frequencies of light to pass through atomic media without being absorbed. However, EIT systems face challenges related to narrow transparency windows and precise control of slow light. We propose an interference structure based on a coupled dual bound states in the continuum (BIC) system to emulate the EIT-like effect. By integrating quasi-BIC (bright mode) with BIC (dark mode), our design successfully achieves an EIT-like effect in a narrow bright mode with a full width at half maximum (FWHM) of less than 1 nm. Its notable features are the bright mode's wide tunability achieved through structural parameter adjustment and a significant group delay of up to 14.43 ps. Additionally, integrating graphene into the BIC structure introduced a form of active tunability akin to the EIT-like effect. We numerically calculate the coupling structure, and its intrinsic mechanism is analyzed. Analysis based on coupled-mode theory confirms that this active modulation primarily stems from changes in the BIC structure's loss. Due to its special frequency selectivity and insensitivity to the polarization of the light source, this narrow-band EIT-like structure is particularly suitable for high-precision optical sensing and spectroscopy. The significant group delay of this structure enhances the interaction between light and matter, improving the accuracy and efficiency of optical signal control and data transmission, opening up new avenues for slow light applications and making significant progress in the development of active tunable optical switches and modulators.