Nanoparticle detection based on microcavity exceptional-point characteristics

We investigate theoretically optomechanically induced transparency in a whispering-gallery-mode microresonator coupled with three nanoparticles. We find that the presence of the third nanoparticle makes the transmission rate more sensitive in the vicinities of exceptional points (EPs). In addition, we also find that adjusting the relative position of the nanoparticles so that the system is near or far from the EPs can realize the switching of the probe light between slow and fast light. Our finding not only provides an alternative way to tune the spread of light but also can identify the existence of the third particle by detecting the change in the output spectrum of light so as to achieve particle detection. Our work may have potential application value in optical signal processing and communication.