Loss-induced Transparency In Optomechanics

In recent years,cavity optomechanics has experienced rapid development.Optomechanical system based on optical microcavities can produce relatively strong optical interactions benefiting from their ultra-high quality factor and small mode volume.Therefore,the optomechanical cavity system can be designed into specific devices for diverse purposes,such as optomechanical sensor,optical diode,and coherent mechanical amplifier.Optomechanical cavities can be also used in many other aspects such as mechanical squeezing,optomechanical entanglement,mechanical cooling,and non-reciprocal light transmission.Parallel to cavity optomechanics,in recent years,the research on exceptional point(EP)in microcavity systems has proliferated.Various systems with EP have emerged,including parity-time symmetric systems,parity-time antisymmetric systems,cavities coupled with nanotip which induces extra loss,and nanoparticles-cavity coupled systems.Recently,research on high-order EP has also emerged.There are many novel physical effects accompanied with EP,such as chiral laser,non-reciprocal light transmission,gaint enhancement of mechanical gain,and slow-to-fast light switch.What is particularly striking is the applications of EP in sensitive sensing based on microcavity systems.Due to the coalescence of the eigenmodes,weak values can be greatly enhanced in the vicinity of EP.This paper is mainly focused on the effects of EP induced by an external nanotip on optomechanically induced transparency,optomechanical second-order sidebands,and group delay in the optomechanical cavity system.The effects of loss-induced EP on purely optical microcavity systems have been studied before.However,its effect on the optomechanical system is to be explored.In this work,we applied the loss-induced EP to the optomechanical system for the first time.We found that loss-induced transparency originally found in pure optical system can also appear in optomechanical system.The loss-induced transparency at the resonance of the pure optical transmission spectrum now is changed to the non-resonant regime in optomechanial system due to the optomechanical interaction.This frequency shift is consistent with that caused by the optomechanical interaction based on our numerical estimation.In addition,we also studied the group delay accompanied with optomechanically induced transparency.We found that there is a fast-to-slow light switch in the vicinity of the EP.The effect of loos-induced EP on high-order sidebands was also studied in this work.The EP induced by nonlinear interaction was observed in the transmission spectrum.Our work has extended the research of EP in optomechanical systems.These results open up a counterintuitive way to engineer micro-mechanical devices with tunable losses for e.g.,coherent optical switch.