Abstract
Tilted fiber Bragg gratings (TFBGs) are now a well-established technology in the scientific literature, bringing numerous advantages, especially for biodetection. Significant sensitivity improvements are achieved by exciting plasmon waves on their metal-coated surface. Nowadays, a large part of advances in this topic relies on new strategies aimed at providing sensitivity enhancements. In this work, TFBGs are produced in both single-mode and multimode telecommunication-grade optical fibers, and their relative performances are evaluated for refractometry and biosensing purposes. TFBGs are biofunctionalized with aptamers oriented against HER2 (Human Epidermal Growth Factor Receptor-2), a relevant protein biomarker for breast cancer diagnosis. In vitro assays confirm that the sensing performances of TFBGs in multimode fiber are higher or identical to those of their counterparts in single-mode fiber, respectively, when bulk refractometry or surface biosensing is considered. These observations are confirmed by numerical simulations. TFBGs in multimode fiber bring valuable practical assets, featuring a reduced spectral bandwidth for improved multiplexing possibilities enabling the detection of several biomarkers.
Highlights
Optical fiber sensors are involved in numerous sensing applications for which continuous monitoring is required [1,2,3]
We reported photo-inscription of Tilted fiber Bragg gratings (TFBGs) in telecommunication-grade multimode optical fiber (MMF) as well as the possibility to generate a plasmonic excitation when a gold layer is deposited on the TFBG surface
We compared the refractometric sensitivities of TFBGs inscribed in gold-coated MMF with those of single mode fiber-based sensors
Summary
Optical fiber sensors are involved in numerous sensing applications for which continuous monitoring is required [1,2,3]. The use of optical fibers for surrounding refractive index (SRI) measurements present several advantages Their size allows the production of very smallscaled optrodes with a diameter of 125 μm only. Incident light to the metal-dielectric interface must be radially-polarized (P-polarization) and feature an identical tangential component to that of the plasmon wave [12] This excitation is characterized by a strong light absorption for some wavelengths as a function of the SRI, which results in a spectral feature in the TFBG spectrum that is strongly sensitive to surface refractive index changes. Compared to SMF-based sensors, MMF-TFBGs offer interesting practical benefits provided that splices with SMF pigtails are properly made They present a more limited spectral bandwidth allowing wavelength multiplexing while being more adequate with an etching process that further improves the sensing performances thanks to a higher core-cladding diameter ratio [36]
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