Real-time sensing on the angular coordinates of nanoparticles using whispering-gallery mode optical microcavities

We theoretically study the scattering-particles–induced field distribution in a whispering-gallery mode optical microcavity system. It is shown that the relative phase angle of the scatters can result in an asymmetric optical distribution. Different from the previous sensing scheme using spectrum scanning whose real time information is limited by the scanning frequency, the proposed scheme could realize the real-time sensing for the angular position of nanoparticles with stable frequency tricolor beams. Numerical simulation is performed to show the performance of the system under different coupling and dissipation condition for the nanoparticles. The scheme may have potential applications in the particle sensing and characterization of both the velocity and angular momentum of the nanoparticles.