2014/09/08 by Florian Sedlmeir, Richard Zeltner, Gerd Leuchs +1 · 154 citations
Engineering · Physics and Astronomy · #Advanced Fiber Laser Technologies #Advanced Fiber Optic Sensors #Birefringence #Magnesium #Magnesium fluoride #Materials science #Optics #Optoelectronics #Photonic and Optical Devices #Physics #Q factor #Refractive index #Resonator #Sensitivity (control systems) #Whispering-gallery wave #physics.optics
paper · pdf · open access · doi:10.1364/oe.22.030934
published in Optics Express 22(25), 30934 (Optica Publishing Group) · 10 pages, 4 figures
arxiv created 2014/09/08 · openalex publication_date 2014/12/04 · arxiv updated 2015/06/22 · openalex created_date 2020/11/23 · openalex updated_date 2026/08/06
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. Compared to fused silica this leads to more than 50% longer evanescent fields and a 4.25 times larger sensitivity. Moreover the birefringence amplifies the sensitivity difference between TM and TE type modes which will enhance sensing experiments based on difference frequency measurements. 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. These data show reasonable agreement with the developed theory. Furthermore, we observe stable Q factors in water well above 1 × 10⁸.