Optical data storage photorefractive polymers

A photorefractive polymer consisting of DMNPAA, TNF, ECZ, and PVK has been used for erasable/rewritable three dimensional bit optical data storage under two-photon excitation. A three dimensional bit density of 5 Gbits/cm(3) is achieved by pulsed beam illumination at an infrared wavelength of 800 nm in the recording process. 

D. Day and M. Gu. Use of two-photon excitation for erasable-rewritable three-dimensional bit optical data storage in a photorefractive polymer. Opt. Lett., 24(14) 948-950, July 1999. 

We have prepared multi-component photorefractive polymers for optical data storage applications (8). This photorefractivity is a combination of two functionalities electro-optic effect and photoconductivity. We have achieved holographic diffraction efficiencies up to >30% in our composites. 

The high optical damage threshold, low dielectric constants, hi photosensitivity, and low cost of photorefractive polymers make them more efficient than inorganic materials (129). Optical data storage in PMMA-based photorefractive polymers has been demonstrated as a cheap and compact way improve data stoi age on compact discs and digital versatile discs (103). Polysiloxane-based photorefractive polymers have demonstrated the highest optical clarity and lowest optical scattering to date (105). 

To overcome volatility problems, two-photon absorption (TPA) is the most promising long-term data storage technique to date. TPA can be observed in all materials and lacks the noncentrosymmetric symmetry requirements of even-order nonlinear optical effects. Nevertheless, in centrosymmetric polymers two-photon absorption is allowed between states that have the same parity according to parity selection rules (112). Such a system has been demonstrated with nondestructive readout (113). Additionally, use of two-photon absorption on photorefractive polymer dispersed liquid crystals has been used to record a high 3D data density of 204.8 Gbits/cm (158). 

---