We explore nonreciprocal transmission behaviors in an optomechanical system, in which two dissipative cavity modes are coupled with each other and also with two parity-time-symmetric mechanical modes. Two cavities, one of which is probed by a weak field, are driven by two strong control fields, respectively. With the active-passive mechanical-resonator scheme, such a closed-loop four-mode system can show an amplification behavior of the probe field with three transmission windows based on optomechanically induced transparency (OMIT). Due to the breaking of the time-reversal symmetry corresponding to the relative phase between two control fields, the amplified nonreciprocal transmission can be realized in the middle OMIT window and its direction can be controlled via the phase modulation. In addition, the system can also show asymmetric group velocities of light propagation, i.e. the tunable asymmetric fast–slow light effects, for example, slow lights along a direction and fast l...

中文翻译：

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具有两个## IMG ## [http://ej.iop.org/images/1555-6611/30/10/105205​​/toc_lpabb1beieqn1.gif]的光机械系统中的不可逆传输和不对称快慢光效果mathcal {PT} $}-对称机械谐振器

我们探讨了在光机械系统中的不可逆传递行为，其中两个耗散腔模式彼此耦合，并且还具有两个奇偶时间对称机械模式。两个空腔分别由两个强控制磁场驱动，其中一个空腔由一个弱磁场探测。通过主动-被动机械谐振器方案，这样的闭环四模式系统可以基于光机械感应的透明性（OMIT）显示具有三个透射窗的探测场的放大行为。由于对应于两个控制场之间的相对相位的时间反转对称性的破坏，可以在中间的OMIT窗口中实现放大的不可逆传输，并且可以通过相位调制来控制其方向。此外，