Spectroscopic ellipsometry has been widely adopted for the measurement of thin film thickness as well as its optical constant. However, conventional ellipsomete
Hollow core fiber (HCF) optical sensors are used in applications including Li-ion battery research and development (R&D), robotic arms, civil engineering infrastructural health monitoring, and biosensing. Some of the attributes of HCF optical sensors are small footprints, non-conductance, chemical stability, and high dynamic ranges. In the case of activities like Li-ion R&D, HCFs can be