1 Tbit/inch² Recording in Angular-Multiplexing Holographic Memory with Constant Signal-to-Scatter Ratio Schedule

Abstract

We developed an iterative method for optimizing the exposure schedule to obtain a constant signal-to-scatter ratio (SSR) to accommodate various recording conditions and achieve high-density recording. 192 binary images were recorded in the same location of a medium in approximately 300×300 µm2 using an experimental system embedded with a blue laser diode with a 405 nm wavelength and an objective lens with a 0.85 numerical aperture. The recording density of this multiplexing corresponds to 1 Tbit/in.2. The recording exposure time was optimized through the iteration of a three-step sequence consisting of total reproduced intensity measurement, target signal calculation, and recording energy density calculation. The SSR of pages recorded with this method was almost constant throughout the entire range of the reference beam angle. The signal-to-noise ratio of the sampled pages was over 2.9 dB, which is higher than the reproducible limit of 1.5 dB in our experimental system.

Linear phase encoding for holographic data storage with a single phase-only spatial light modulator

“…Unlike two-axis holography [37][38][39], signal and reference beams propagate along a common optical axis, and thus the optical setup is compact and simple. Moreover, the optical setup has high stability against vibration and wavelength shift [40].…”

“…Although there is symbol error in the reconstructed data page 2, in the case that the SER is less than 10 −1 the original data page can be obtained by using an error correction code [36]. Alternatively, homogenizing the SNRs with schedule recording [39] is a solution to reduce the SER. The experimental results show that the coaxial system with the linear phase coding enables shift multiplexing in an optical system with a single phase-only SLM.…”

Multiplexed recording with uncorrelated computer-generated reference patterns in coaxial holographic data storage

“…To unify the SNRs in Figs. 6(b) and 6(c), optimizing exposure time is required [25,26]. The experimental results mean that the proposed method can suppress the crosstalk and implement multiplexed recording without shifting a medium.…”

Cavity enhanced image recording for holographic data storage

“…Since HDSS usually multiplexes several hundred holograms the diffraction efficiency of each hologram is very low 19 . Typical diffraction efficiencies are less than 0.3% for readout, so most of the readout power is wasted 19,20 .…”