Label-Free Detection of Ultra-Low Weight Molecules Based on Fiber Optic Sensors With Low Loss Dielectric Nanostructures

Abstract

Fiber optic (FO) sensors have great potential for low-cost, microsample testing and compact medical diagnostics. In this work, a FO sensor based on dielectric nanostructure is proposed and demonstrated based on the unique characteristics of dielectric materials, such as low ohmic loss and good biocompatibility. Specifically, we fabricate a SPR-FO sensor by inserting a sleeve with a large-scale, highly ordered dielectric nanodisk array at the end of the fiber probe. And we systematically investigate the sensing performance of the FO sensor including bulk and surface sensitivities. It is found that due to very low absorption losses, the FO sensor based on dielectric nanodisk exhibits a narrow resonance, thus leading to a sensing figure-of-merit almost twice larger than that of based on the metal plasmonic nanodisk. Also, the FO sensor shows a linear response to adsorbate layer thickness changes, which is clearly advantageous for quantitative analysis. Due to the highly localized electromagnetic fields, it can detect small molecules with a concentration of 1 μM, in which a molecular layer with thickness less than 1 nm can produce resonance changes as large as 6 nm. Our work could open a new opportunity for future bio-compatible, robust and low-loss medical diagnostic devices.