Is there a frontier in sensitivity with lossy mode resonance (LMR) based refractometers?

A tin dioxide thin layer has been studied in order to improve the sensitivity of lossy mode resonances (LMR) based sensors. The effects of the thin film thickness and the polarization of light in a SnO2 coated D-shaped single mode optical fiber have been evaluated. The optimization of such parameters in the fabrication of refractometers have led to an unprecedented sensitivity of over one million nanometers per refractive index unit (RIU), which means a sensitivity below 10^(−9) RIU with a pm resolution detector. This achievement is a milestone for the development of new high sensitivity devices and opens the door to new industrial applications, such as gear oil degradation, or biomedical devices where previous devices could not provide enough sensitivity.The authors would like to acknowledge the partial support to the Spanish Ministry of Economy and Competitiveness TEC2016-79367-C2-2-R research funds, the Spanish Ministry of Education FPU15/05663 predoctoral research grant, the Public University of Navarre (UPNA) pre-doctoral research grant and Government of Navarre 2016/PC026 BIOPTSENS and 64/2015 research funds