Spectral characteristics and time dynamics of tunable acoustic resonators in the strong coupling regime

Strong coupling between resonant systems is one of the remarkable phenomena in different areas of physics such as condensed matter physics, quantum optics, nanophotonics, and plasmonics. However, the strong coupling regime is often hardly achievable because it requires special experimental conditions, which ensure an increase in the coupling strength and the reduction of losses in interacting systems. A transition from the weak coupling regime to the strong coupling regime is demonstrated in this work in the system of coupled Fabry–Pérot acoustic resonators, where the coupling strength is larger than the characteristic losses in resonators by a factor of 3.5. The strong coupling regime is demonstrated in both the spectral and time domains. The results are important for the development of modern acoustic systems implementing, in particular, the slow sound regime or regimes serving for the high-$Q$-factor frequency filtering and highly sensitive acoustic detection.