Magnetic-field tuning whispering gallery mode based on hollow microbubble resonator with Terfenol-D-fixed

We propose a method of magnetic-field tuning whispering gallery modes (WGMs) based on a hollow microbubble resonator (HMBR) with Terfenol-D-fixed. WGMs are excited by the evanescent field from a tapered fiber coupling with an HMBR. Both ends of the HMBR are fixed with Terfenol-D and vary with different lengths of the Terfenol-D. The length of the Terfenol-D varies with the external magnetic field for the high magnetostriction coefficient of Terfenol-D. The magnetic field sensitivity of 0.081 pm/mT in the magnetic field range of 0.14 mT–21.8 mT is achieved. The $Q$Q-factor of the HMBR can be regulated up to ${2.07} \times {{10}^4}$2.07×104 with physical stretching HMBR. This work provides a novel tuning whispering gallery mode scheme and a broad application prospect in the fields of optical measurement and precise optical clocks in the future.