Fig. 3: Efficiency of the optomechanical coupling.
From: Active optomechanics
a Energy transfer from the laser light to the spring–mass oscillator. Initially, the positions of two mirrors of the optical cavity are fixed and the intracavity field reaches the steady state. Then, the moveable mirror is free to move. The radiation pressure \({F}_{{{{{{\rm{rad}}}}}}}(t)\) pushes the movable mirror away from the initial position \(x(t=0)=0\). As the time goes infinity, \(t\to \infty\), the position of the movable mirror approaches the steady-state displacement \(x(t=\infty )={x}_{{{{{{\rm{ss}}}}}}}\). During this process, the radiation pressure does the work \(W={\int }_{t=0}^{t=\infty }{F}_{{{{{{\rm{rad}}}}}}}(t)dx(t)\). When the moveable mirror is displaced at \({x}_{{{{{{\rm{ss}}}}}}}\), the potential energy stored in the spring–mass oscillator is \(U\). The energy conversion efficiency from \(W\) to \(U\) is given by \(\eta =U/W\). b Efficiency \(\eta\) vs. the pump rate \(R\) for different cavity \(Q\) factors. Here, \({R}_{0}\) is the minimum pump threshold. The atom–cavity detuning is set at \(\Delta =-\kappa\) with the cavity loss rate \(\kappa\).
