Lensless complex amplitude demodulation based on deep learning in holographic data storage

To increase the storage capacity in holographic data storage(HDS),the information to be stored is encoded into a complex amplitude.Fast and accurate retrieval of amplitude and phase from the reconstructed beam is necessary during data readout in HDS.In this study,we proposed a complex amplitude demodulation method based on deep learning from a single-shot diffraction intensity image and verified it by a non-interferometric lensless experiment demodulating four-level amplitude and four-level phase.By analyzing the correlation between the diffraction intensity features and the amplitude and phase encoding data pages,the inverse problem was decomposed into two backward operators denoted by two convolutional neural networks(CNNs)to demodulate amplitude and phase respectively.The experimental system is simple,stable,and robust,and it only needs a single diffraction image to realize the direct demodulation of both amplitude and phase.To our investigation,this is the first time in HDS that multilevel complex amplitude demodulation is achieved experimentally from one diffraction intensity image without iterations.

掺杂LiNbO_3晶体生长及在体全息存储方面的应用研究

In this paper,the Fe:LiNbO 3,Ce:Fe:LiNbO 3 and Ce:Mn:LiNbO 3 crystals with n o defect,were grown from melt by Czochraski technique.The two doped LiNbO 3 cry stals were treated by heating reduction in Li 2O 3 powder,and Fe:LiNbO 3 crys tals were oxidized in air. The measurments on lattic constants and the absorption spectrum show that the doped crystals’ structure are regular and the optical pr operties are good.The absorption spectra,diffractive efficency,response time,sen sitivity,and photoconduction were measured.The properties of Ce:Fe:LiNbO 3 crys tals are η sat =0.25, Sη -1 =16.2mJ/mm 2, τ E/ τ W=6 .5, σ =2.99×10 -17 ;and the properties of Ce:Fe:LiNbO 3 crystals are η sat =0.70, Sη -1 =4.6mJ/mm 2, τ E/ τ W=7.2, σ =5. 42×10 -17 . The response speed of two doped LiNbO 3 crystals is faster than that of Fe:LiNbO 3 crystals.The diffractive efficiency was measured to be high er than 80% and with a broad angle range.Fe:LiNbO 3 crystals were oxidized in air in order to make the storage time longer and strength the diffractive effici ency.So it is a good kind of Volume Holographic memory materials.And it is shown in our experiment that Ce:Fe:LiNbO 3 crystals is more sensitive to 633nm than Fe:LiNbO 3 crystals,it is more fit for He Ne laser and is a better materials o f Volume Holographic Storge.

A two-dimensional constant-weight sparse modulation code for volume holographic data storage

In order to simplify the threshold determination,reduce the inter-pixel cross-talk,and improve the storage density for high-density volume holographic data storage,a two-dimensional constant-weight sparse modulation code is proposed.The evaluation criteria and design rules are investigated based on the page-oriented optical data storage system.Coding parameters are optimized to achieve large channel capacities.An 8:16 modulation code is designed to reduce the raw bit error rate and its performances are experimentally evaluated.A raw bit error rate of the magnitude of 10 4 is obtained with a single-data-page storage and 10 3 with multiplexing.

Improved phase retrieval in holographic data storage based on a designed iterative embedded data

Embedded data are used to retrieve phases quicker with high accuracy in phase-modulated holographic data storage(HDS).We propose a method to design an embedded data distribution using iterations to enhance the intensity of the high-frequency signal in the Fourier spectrum.The proposed method increases the antinoise performance and signal-to-noise ratio(SNR)of the Fourier spectrum distribution,realizing a more efficient phase retrieval.Experiments indicate that the bit error rate(BER)of this method can be reduced by a factor of one after 10 iterations.