Large reversible upconversion luminescence modification and 3D optical information storage in femtosecond laser irradiation-subjected photochromic glass

Fast response, high luminescence contrast, three-dimensional (3D) storage, and nondestructive reading are key factors for the optical storage application of photochromic materials. Femtosecond (fs) laser direct writing technology with multiphoton nonlinear absorption is becoming a useful tool for microprocessing functional units in the 3D space of glass owing to its remarkable advantages, such as a fast processing speed and high processing accuracy. Herein, the photochromism of transparent glass codoped with rare-earth ions was investigated under 800-nm fs laser irradiation, affording a fast response. The photochromic glass achieves an upconversion luminescence (UCL) modification of 92%. The photochromic glass can be bleached back to its original color using heat treatment. The transmittance and UCL modification show excellent reproducibility under alternating stimulations between 800-nm fs laser irradiation and heat treatment. The data can be written in the interior of the transparent photochromic glass using 800-nm fs laser irradiation, facilitating 3D information storage. These results suggest that the 800-nm fs laser irradiation-subjected photochromic glass is an ideal optical data storage medium.