Multi-layer Optical Data Storage Based on Two-photon Recordable Fluorescent Disk Media

Abstract

In this paper, we present a technology that can be used for random accessed mass optical data storage. The technology uses a two-photon recordable plastic disk medium that can fluoresce when recorded and that can support multiple stored data layers inside one disk. This technology is capable of achieving 200GB data capacity with a 120mm diameter, 10mm thick disk, and a data transfer rate of Gigabits/Sec by using parallel readout. IntroductionSince the amount of digital information is growing very fast and access to this information is made via faster and faster networks, data storage systems needs to keep pace with this explosive growth. High capacity data storage devices with high-speed data transfer rate and capable of random access are already in high demand. One approach to satisfy this demand is to increase the areal storage density. Unfortunately, for many of the conventional optical storage technologies this is becoming increasingly costly and technically challenging. Another direction to increase the data capacity is to stack multiple layers in one disk. This requires a new means of recording data in multiple layers closely packed together but with minimum interlayer crosstalk. The two-photon absorption based recording approach pioneered by Call/Recall Inc. uses the volume of suitable disk media enabling recording of highly packed multiple data layers at desired locations achieving very high volumetric densities [1,2,3,4,5]. Call/Recall Inc. has developed several kinds of two-photon recordable fluorescent WORM (Write Once Read Many) media. When recorded by two-photon absorption the recorded bits fluoresce when excited by a suitable readout laser beam. The recorded area in our materials is non-reflective and has no noticeable index change for both readout and recording enabling optical beams to access the volume of the disk without significant aberrations and losses. These properties allow the recording and readout beam to access multiple layers even in parallel. We should note that there are also possible approaches that use the index change [6,7,9] or photon bleaching [8] to store information by twophoton absorption but these approaches generally limit optical access to only a few layers. This paper presents the recording and readout systems and associated performances for single channel and parallel channels implementations.

Three-dimensional optical data storage in a novel photochromic material with two-photon writing and one-photon readout

“…Lower readout power can increase the readout cycle times, 22 whereas suitable fluorescence bandpass and the dichroic mirror and confocal pinhole are used to block stray light from out-of-focus planes to increase the SNR. 23 In our case after optimization, we got SNRs up to 27.1 dB.…”

Low Level Signal Processing for the Optoelectronic Memory System Interface

“…A typical setup for a two-photon optical memory 5,6 is shown in Figure 1. The data is read from memory in pages.…”

Real-time adaptive encoding for 3D optical memories

“…A typical setup for a two-photon optical memory [5] is shown in Figure 1. The data is read from memory in pages.…”