Two-photon-induced polarization-multiplexed and multilevel storage in photoisomeric copolymer film

We present a two-photon-induced polarization-multiplexed and multilevel data storage method with a bisazobenzene copolymer film. A polarization-adjustable femtosecond pulsed laser is used as writing beam to induce anisotropy, and the recorded information is retrieved by a CCD sensor from the film with corresponding polarized illumination. It is found that the optical axis of bisazobenzene molecules can be reoriented under two-photon excitation by the polarized femtosecond laser via a photoisomerization process. Polarization-multiplexed and multilevel storage is demonstrated by using this method. The capability to combine both advantages of these distinct techniques makes it a novel approach to obtain higher optical data density.