Single-beam two-photon-recorded monolithic multi-layer optical disks

Both single and two-beam recording for two-photon monolithic multilayer optical storage are under development at Call/Recall, Inc. The depth resolution using single beam recording is less due to the intensity distribution properties of laser beam. Using short pulse mode-locked Ti:Sapphire laser and narrowed aperture CD lens, a single beam recorded 25-layer fluorescence disk has been demonstrated and evaluated in cross-talk and recorded mark shape. The results indicate designing an optical system with high NA and aberration compensation for different depth is essential for high data capacity using one beam recording. Several potential solutions exist, and preliminary experiments indicate that by simply narrowing the objective aperture, the depth uniformity can be improved without significantly compromising mark size.