Phase-enhanced nonreciprocal photon-phonon conversion via coupled optomechanical cavities

Abstract

Nonreciprocity, characterized by direction-dependent signal propagation, is fundamental to technologies such as isolators, signal routing, and precision sensing. This letter theoretically demonstrates nonreciprocal phonon transport and the conversion between photon and acoustic phonon signals in coupled optomechanical cavities via phase-dependent driving. It is demonstrated that, in contrast to nonreciprocal phonon transport, which necessitates both dissipation and phase-induced violation of time reversal symmetry, the nonreciprocity in photon-phonon conversion can occur without violating time reversal symmetry. We demonstrate that such nonreciprocity arises due to the path-dependent asymmetry in photon-phonon conversion. Furthermore, we demonstrate that the nonreciprocity of photon-phonon conversion can be further enhanced, achieving isolation levels of up to 40 dB by suitably modifying the phase difference of the driving lasers.

Figures (4)

• Figure 1: Schematic diagram of the two coupled optomechanical cavities. The optical modes (red) are coupled via photon hopping $J$, while the mechanical modes (blue) are coupled via phonon hopping $V$, and the optomechanical coupling by $G_j$. The operators ${a}_j$ and ${b}_j$ represent the optical and mechanical field modes, respectively, while $\kappa_{e j}, \gamma_{e j}$ external optical and mechanical decay rates, respectively.
• Figure 2: (a) Isolation describing the ratio of forward and backward phonon signal transport for three different values of the synthetic flux $\phi$, and (b) Dependence of the phonon isolation on the synthetic flux $\phi$ and frequency $\omega$.
• Figure 3: (a) Isolation describing the ratio of the forward and backward nonreciprocal conversion of an input photon signal into a phonon signal for three different values of the synthetic flux $\phi$. (b) Dependence of the photon-to-phonon conversion on the synthetic flux $\phi$ and frequency $\omega$, demonstrating phase-controlled nonreciprocity.
• Figure 4: (a) Isolation describing the ratio of the forward and backward nonreciprocal conversion of an input phonon signal into an optical photon signal for three different values of the synthetic flux $\phi$. (b) Dependence of the phonon-to-photon conversion on the synthetic flux $\phi$ and frequency $(\omega-\omega_{d})$, demonstrating phase-controlled nonreciprocity.