Distance and Temperature Sensing Fluorosilicate Glass with Modulated Upconversion Luminescence

ABSTRACT Achieving dynamic modulation of upconversion luminescence (UCL) in a monolithic rare‐earth‐ion‐doped glass is challenging. In this study, novel high YbF 3 ‐content fluorosilicate glasses (SiO 2 ‐KF‐YbF 3 ‐ErF 3 ) doped with Er 3+ were fabricated, which exhibit noticeable variation of UCL color with excitation power density. The green‐to‐red UCL intensity ratio (G/R) of the glass demonstrates a wide tuning range from 0.24 to 2.48. This significant variation in the G/R ratio was visually manifested as the color and CIE chromaticity coordinate transitions from red to yellow and to green. A visual method of distance sensing was established with the sensing precision of approximately 80 µm. The glass was also endowed with temperature‐sensing ability based on both Er 3+ thermally coupled levels ( 2 H 11/2 and 4 S 3/2 ) and non‐thermally coupled levels ( 2 H 11 / 2 and 4 F 9/2 ), achieving maximum relative sensitivities of 0.83 and 0.65% K −1 at 323 K, respectively. These findings underscore a promising material platform for developing non‐contact robust multifunctional optical sensors.