Novel chip-scale high-Q whispering gallery mode resonator as a magnetometer

We present a novel magnetometer consisting of chip-scale whispering gallery mode resonators with high-g factors (>10⁶) realized using MEMs fabrication techniques. A permanent magnet is elastically coupled to a whispering gallery mode borosilicate microbubble. Magnetic forces from applied external magnetic fields induce deformation in the microbubble which can be sensitively monitored through changes in the optical resonance characteristics. We calculate the force and simulate the resultant deformation in the microbubble. The effect of different permanent magnet orientations and microbubble shell thickness is experimentally investigated and modeled. We experimentally demonstrate a large sensitivity of 1.9 GHz/mT on a microbubble with 1.1 μm shell thickness.