Ultra-slow-light and dynamically quantitative optical storage modulation via quasi-BICs

Abstract

We achieve dynamically tunable dual quasi-bound states in the continuum (quasi-BICs) by implementing them in a silicon–graphene multilayer composite structure and utilize the quasi-BIC modes to achieve ultra-large group delays (velocity of light slows down 105 times), showing 2–3 orders of magnitude higher than the group delays of previous electromagnetically induced transparency modes. The double-layer graphene holds great tuning capability and leads to the dramatically reduced group delay from 1929.82 to 1.58 ps with only 100 meV. In addition, the log-linear variation rule of group delay with Fermi level (Ef) in the range of 0–10 meV is analyzed in detail, and the double-logarithmic function relationship between the group delay and quality factor (Q-factor) is theoretically verified. Finally, the quantitative modulation of the optical storage is further realized in this basis. Our research provides ideas for the reform and upgrading of slow optical devices.