Phonon-phonon interaction and parametric down-conversion generation in multimode optomechanical systems

We studied the process of polariton conversion in a 3-mode nonlinear optomechanical system. Compared with the standard 2-mode optomechanical system, we find a much larger conversion rate of polariton modes can be achieved under typical dissipation conditions. To obtain a transparent understanding of the relevant physical process, we show that in the large detuned case, the cavity can be eliminated adiabatically, resulting in a parametric down-conversion (PDC) interaction between two phononic polariton modes. By tuning cavity detuning, the nonlinear interaction can be enhanced with the frequency-matching condition. Results from analytical treatment based on the effective PDC model agree with the numerical simulation. Such a system provides potential applications in nonlinear phononics.

Automated summary

We investigated the process of polariton conversion in a 3-mode nonlinear optomechanical system and found a higher conversion rate compared to the standard 2-mode system. By adiabatically eliminating the cavity in the large detuned case, we achieved a parametric down-conversion interaction between two phononic polariton modes. The nonlinear interaction can be enhanced by tuning the cavity detuning, which was confirmed through analytical treatment and numerical simulation. This system holds potential applications in nonlinear phononics.