Coherent Phonon Spectroscopy and Photo-Induced Ultrafast Phase Transition in Phase-Change Optical Data Storage Media(Current Topics)

Abstract

Multi-component chalcogenides, such as Ge_2Sb_2Te_5, are potentially used in optical data storage media in the forms of rewritable DVDs, and Blu-ray discs. Irradiating Ge_2Sb_2Te_5 with laser pulses induces phase transition between the amorphous and crystal. Since optical reflectivity is significantly different in the two states, the material has been used in optical memories. Recently, by monitoring coherent phonons excited by femtosecond laser pulses in Ge_2Sb_2Te_5, it becomes possible to induce and observe the phase transition in the ultrafast time scale of sub-picoseconds. Here we report the recent progress of the ultrafast phase transition observed in optical data storage media.