Ultra-sensitive fiber optic cryogenic liquid level sensor by irradiating Gaussian and non-Gaussian beam: a novel technique based on wave theory

Abstract

A novel analytical technique for the level detection of cryogenic liquids like liquid nitrogen using wave theory and employing a Gaussian beam, a zeroth-order Bessel-Gauss (BG) beam, and a radially polarized Bessel-Gauss (RPBG) beam is presented here. At first, this wave theory-based analytical model is shined by the Gaussian (G) beam, and the observations are validated with the already reported experimental data. The obtained results are in good concurrence with the experimental findings presented by J. E. Antonio-Lopez et al. in the year 2011. With this validation of the proposed theory, this idea next extended to the utilization of Gaussian, BG, and RPBG beams as input sources for the proposed structure. The performance of this sensor with the change in refractive index according to the cryogenic temperature and the level of liquid nitrogen is investigated using the propagation of these beams inside the sensor structure. A comparative assessment has also been presented utilizing the Gaussian and non-Gaussian beams. By irradiating the RPBG beam, the discerned sensitivity is 4.517 dB/°K, 18458.8 dB/RIU, 9.759 dB/cm, and 0.176 dB/nm, with a resolution of 5.5 × 10⁻⁷ RIU. This is 3.8 times more sensitive than the published ray theory-based publications till date that are based on the Gaussian beam. Due to its better sensing performances, with the ease of fabrication processes, the proposed sensing technology opens new avenues to develop high-performance fiber optic-level sensors with the scope of multiple input sources for physical, biological, and chemical sensing in cryogenic environments.