Femtosecond laser-induced birefringent voxels were explored by using birefringent microscope and optical microscope. It shows that the retardance increases as the pulse number increases. Two types of structures are found. Type X structures require at least 20 pulses and single pulse energy no more than 854 nJ. More， the pulse duration must limited between 300 fs and 600 fs. Additionally， the data storage process is presented by taking Chinese characters of "Acta Photonica Sinica" as example. Time capsules containing the history of Jilin Province， the history of Jilin University， and the history of Tsinghua University are prepared.