Abstract
Ultrahigh density data storage is in high demand in the current age of big data and thus motivates many innovative storage technologies. Femtosecond laser induced multi-dimensional optical data storage is an appealing method to fulfill the demand of ultrahigh storage capacity. Here we report a femtosecond laser induced two-stage optical storage in bisazobenzene copolymer films by manipulating the recording energies. Different mechanisms can be selected for specified memory use: two-photon isomerization (TPI) and laser induced surface deformation. Giant birefringence can be generated by TPI and brings about high signal-to-noise ratio (>20 dB) multi-dimensional reversible storage. Polarization-dependent surface deformation arises when increasing the recording energy, which not only facilitates the multi-level storage by black bits (dots), but also enhances the bits' readout signal and storing stability. This facile bits recording method, which enables completely different recording mechanisms in an identical storage medium, paves the way for sustainable big data storage.
Highlights
As vast amount of information is newly generated every day in the fields of economics, education, health, business, and so on [1, 2], it becomes extremely challenging to store such amount of data by using our current information storage technologies
We have demonstrated that two recording mechanisms: photoinduced birefringence and surface-mediated data recording, can be applied in the same polymer film
The first stage recording enables high-signal-to-noise ratio (SNR) fourdimensional storage from which different information can be encoded in the same layer by selecting the recording polarization
Summary
As vast amount of information is newly generated every day in the fields of economics, education, health, business, and so on [1, 2], it becomes extremely challenging to store such amount of data by using our current information storage technologies. Multi-dimensional storage, in which other physical dimensions are integrated inside the identical domain of recording medium, is regarded to be a superior approach for capacity improvement. It is able to increase the storage capacity by orders of magnitude without changing the recording wavelength and numerical aperture of objective [12]. Spatially multi-layer [4], recording wavelength [3, 13], polarization [5, 12] and bits gray-level [5, 14,15,16] have been successfully exploited as the extra-dimension of data recording, enabling the storage capacity to the order of terabytes per disc. The surfacemediated data recording is thought to be able to enhance the bits signal intensity and based on which, quasi-permanent multi-gray level storage is demonstrated
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