High-Q MgF₂ whispering gallery mode resonators for refractometric sensing in aqueous environment.We present our experiments on refractometric sensing with ultrahigh-Q, crystalline, birefringent magnesium fluoride (MgF₂) whispering gallery mode resonators.  The difference to fused silica which is most commonly used for sensing experiments is the small refractive index of MgF₂ which is very close to that of water.  We estimate the performance of our resonators and compare them with fused silica theoretically and present experimental data showing the interferometrically measured evanescent field decay and the sensitivity of mm-sized MgF₂ whispering gallery mode resonators immersed in water. 
MgF₂
High-Q MgF₂ whispering gallery mode resonators for refractometric sensing in aqueous environment.We present our experiments on refractometric sensing with ultrahigh-Q, crystalline, birefringent magnesium fluoride (MgF₂) whispering gallery mode resonators.  We estimate the performance of our resonators and compare them with fused silica theoretically and present experimental data showing the interferometrically measured evanescent field decay and the sensitivity of mm-sized MgF₂ whispering gallery mode resonators immersed in water. 
whispering gallery mode resonators