Highly tunable quasi-bound states in the continuum responses in subwavelength plasmonic-dielectric hybrid nanostructures

Here, we study the quasi-bound states in the continuum (Q-BIC) response in subwavelength hybrid nanostructures consisting of plasmonic antennas and subwavelength dielectric cavities. Among them, the plasmonic antennas are metal nanorods with electric dipole resonances, and the dielectric cavity is a nanodisk with an anapole mode. By reasonably adjusting the phase difference between the two modes, we can excite Q-BIC mode in the hybrid cavity. As the two modes involved in the construction of Q-BIC are on two separate structures, the Q-BIC of this hybrid nanostructure has great adjustability, and the quality factor of resonant mode can be increased several times. Our research enriches the generations of Q-BIC mode in subwavelength cavities, which may help to enhance light-matter interaction.