BUSCADOR RECOLECTA

This study presents a novel sensor design utilizing a long-period fiber grating (LPFG) deposited with a TiO2 nanocoating via atomic layer deposition. The study combines theoretical simulations and experimental validation to optimize the grating period and modulation index to operate in the mode transition with a quasi-lossy mode resonance (LMR) behavior, i.e., the LPFG attenuation bands shift similarly to LMRs. This enables the achievement of a remarkable sensitivity of 78 nm/nm, allowing for the detection of sub-angstrom variations in film thickness, which is critical for applications in semiconductor manufacturing. Our setup facilitates continuous monitoring of the transmission spectrum, enabling real-time adjustments during deposition to maximize sensitivity. As proof of concept for the applicability of the sensor as a refractive index sensor, we demonstrated exceptional sensitivity for nitrogen detection, achieving around 10,000 nm/RIU, with a figure of merit of 200. This marks one the highest sensitivities reported for optical fiber gas sensors and suggests this technology could revolutionize the field duet to its simplicity in terms of sensor design., This work was supported in part by the Agencia Estatal de Investigación (AEI) from the Spanish Ministry of Economy and Competitiveness (MCIU/AEI/10.13039/501100011033/FEDER PID2023-149895OB-I00) research fund and by the pre-doctoral research grant of the Public University of Navarra.

This paper introduces the fabrication and characterization of a regenerable LMR-based, label-free optical fiber immunosensor. This innovative biosensor proposal was developed by functionalizing a SnO2 metallic oxide thin film deposited on a D-shaped optical fiber using a silanization protocol. The system successfully detected IgG - anti-IgG complexes in real-time in a range of concentrations from 0.5 to 10 ¿g/ml and achieved a limit of detection (LoD) of 0.12 μg/ml of anti-IgG. The biosensor was extensively tested to assess its capacity for regeneration, confirming that it can be reused repeatedly, reducing the overall cost and waste typically associated with disposable sensors. This regenerability has significant implications for a range of applications, providing a more sustainable and flexible approach to biosensing technology., This research was funded partially by the Spanish Agencia Estatal de Investigacion (MCIU/AEI/10.13039/501100011033/FEDER) through the project with reference PID2023-149895OB-I00, and also by the Public University of Navarre pre-doctoral research grant.