Enhancement of Quality Factor in Gain-Assisted Acoustic Resonance Systems

Damped acoustic systems have a limited quality factor due to intrinsic loss. By introducing gain elements, a method to enhance the quality factor of damped systems is proposed based on the concept of bound states in the continuum (BICs). The acoustic model under study is a two-port waveguide system installed with two side Helmholtz resonators connected by a coupling tube. Based on the temporal coupled-mode theory, a Hamiltonian matrix with both intrinsic and radiation losses is used to characterize the resonance behavior of the coupled resonators. To achieve a high quality factor, acoustic gain is introduced to compensate the intrinsic loss, leading the Hamiltonian parameters toward a quasi-BIC condition. Numerical simulation demonstrates a gain-assisted and quasi-BIC-supported extremely high quality factor in damped acoustic systems. The concept is further utilized to design a sensor model for particle size detection. The enhanced sensing performance due to high quality factors is numerically demonstrated. The findings suggest potential applications in acoustic sensing and detection devices.