We theoretically study an optomechanical system which consists of a two-sided cavity and a mechanical membrane that is placed outside of it. The membrane is positioned close to one of its mirrors, and the cavity is coupled to the external light field through the other mirror. Our study is focused on the regime where the dispersive optomechanical coupling in the system vanishes. Such a regime is found to be possible if the membrane is less reflecting than the adjacent mirror, yielding a potentially very strong dissipative optomechanical coupling. Specifically, if the absolute values of amplitude transmission coefficients of the membrane and the mirror, $t$ and $t_m$, respectively, obey the condition $t_m^2<t\ll t_m\ll 1$, the dissipative coupling constant of the setup exceeds the dispersive coupling constant for an optomechanical cavity of the same length. The dissipative coupling constant and the corresponding optomechanical cooperativity of the proposed system are also compared with those of the Michelson-Sagnac interferometer and the so-called “membrane-at-the-edge” system, which are known for a strong optomechanical dissipative interaction. It is shown that under the above condition, the system proposed here is advantageous in both aspects. It also enables an efficient realization of the two-port configuration, which was recently proposed as a promising optomechanical system, providing, among other benefits, a possibility of quantum limited optomechanical measurements in a system which does not suffer from any optomechanical instability.

中文翻译：

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耗散光机械耦合与光学腔外的膜

我们从理论上研究了一个光机械系统，该系统由一个两侧的腔体和一个放置在其外部的机械膜组成。薄膜靠近其中一个反射镜放置，腔体通过另一个反射镜耦合到外部光场。我们的研究集中在系统中色散光机械耦合消失的状态。如果膜比相邻的反射镜反射更少，则发现这种机制是可能的，从而产生潜在的非常强的耗散光机械耦合。具体来说，如果膜片和反射镜的振幅透射系数的绝对值，$吨$ 和 ${吨}_{米}$，分别服从条件 ${吨}_{米}^2<吨\ll {吨}_{米}\ll 1$，装置的耗散耦合常数超过了色散相同长度的光机腔的耦合常数。所提出系统的耗散耦合常数和相应的光机协同性也与迈克尔逊-萨格纳克干涉仪和所谓的“边缘膜”系统进行了比较，后者以强光机耗散相互作用而闻名。表明在上述条件下，这里提出的系统在这两个方面都具有优势。它还能够有效实现双端口配置，该配置最近被提出作为一种有前途的光机械系统，除其他好处外，还提供了在不受任何光机械不稳定性影响的系统中进行量子限制光机械测量的可能性。