Characterization of a preliminary narrow-band absorption material for holographic data storage

A new holographic data storage material is currently being developed at General Electric. This material is based on a thermoplastic host doped with dyes with narrowband absorption resonances. The dye is photosensitive and irreversibly bleaches under exposure to light. The reduction in concentration of the dye in the host after exposure induces refractive index variations at wavelengths away from the dye absorption peak according to the well-known Kramers-Kronig relationship. The approach proposed here requires different recording and readout wavelengths to prevent data erasure during readout. Samples were produced using different dyes and various concentrations in a polycarbonate host. The extensive experience developed in the past with polycarbonate for optical media promises to make the proposed material very inexpensive. These samples were characterized using holographic techniques as well as using spectroscopic transmission and ellipsometry. The results of the characterizations indicate that this material approach can offer very large dynamic range, but have thus far shown very low sensitivity. Further work is required to demonstrate materials having both sufficient dynamic range and sensitivity for holographic storage applications. We believe that if this condition can be satisfied, this new material approach will be an excellent candidate for high-density holographic media for content distribution.