Optically manipulated micromirrors for precise excitation of WGM microlasers

Whispering gallery mode microlasers are highly sensitive refractive index sensors widely explored for biophotonic and biomedical applications. Microlaser excitation and collection of the emitted light typically utilize microscope objectives at normal incidence, limiting the choice of the oscillation plane of the modes. Here, we present a platform that enables the excitation of microlasers from various directions using an optically manipulated micromirror. The scheme enables precise sensing of the environment surrounding the microlasers along different well-controlled planes. We further demonstrate the capability of the platform to perform a time-resolved experiment of dynamic sensing using a polystyrene probe bead orbiting the microlaser.