Noise Attenuation of a Duct-resonator System Using Coupled Helmholtz Resonator - Thin Flexible Structures

Several studies have been devoted to increasing the attenuation performance of the Helmholtz resonator (HR). One way is by periodic coupling of HRs in a ducting system. In this study, we propose a different approach, where a membrane (or a thin flexible structure in general) is added to the air cavity of a periodic HR array in order to further enhance the attenuation by utilizing the resonance effect of the membrane. It is expected that three attenuation mechanisms will exist in the system that can enhance the overall attenuation, i.e. the resonance mechanism of the HR, the Bragg reflection of the periodic system, and the resonance mechanism of the membrane or thin flexible structure. This study found that the proposed system yields two adjacent attenuation peaks, related to the HR and the membrane respectively. Moreover, extension of the attenuation bandwidth was also observed as a result of the periodic arrangement of HRs. With the same HR parameters, the peak attenuation by the membrane is tunable by changing its material properties. However, such a system does not always produce a wider attenuation bandwidth; the resonance bandwidths of both mechanisms must overlap.

Controllable Fast and Slow Light in the Hybrid Nanomechanical Resonator System

We propose a hybrid nanomechanical resonator (NR) system, where a NR coupled to an embedded quantum dot (QD) driven by two-tone fields is also coupled to another NR via the Coulomb interaction, and investigate the absorption spectra of the probe field under both the condition of resonance and off-resonance. The absorption spectra in resonance presents a means to determine the coupling strength of the two NRs. In the off-resonance, the absorption spectra can exhibit double Fano resonance, and the positions of the double Fano resonances are related to the interaction of the two NRs, the frequencies of the NRs, and the pump detuning. Furthermore, the double Fano resonances are accompanied by the rapid normal phase dispersion, which indicates the slow- and fast-light effect. We can obtain that the group velocity index is tunable by the interaction between the two NRs, the detuning, and the different resonator frequencies, which can reach the conversion from the fast light to slow light.