Absorption effects in photorefractive volume-holographic memory systems I Beam depletion

Campbell, Scott; Lin, Shiuan Huei; Yi, Xianmin; Yeh, Pochi

doi:10.1364/josab.13.002209

Cited by 7 publications

(6 citation statements)

References 17 publications

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“…The detected wavefront could either be directly imaged from the SLM, or recorded and reconstructed from a hologram placed somewhere in the optical path. By assuming that the storage and reconstruction of this data-bearing wavefront by a hologram does not significantly alter it, we implicitly neglect any optical aberrations introduced by the holographic media, inter-page crosstalk, optical scatter, further band limiting from an insufficiently large reference beam, the effects of material absorption and recording nonlinearities, 26 and other effects such as beam coupling or photovoltaic-induced index changes. 1,2 Because we retained the a priori information from the original SLM pattern, the signals obtained for each detector pixel could be separated into the two appropriate classes ͑ON or OFF pixels͒.…”

Section: Review Of the Methodsmentioning

confidence: 99%

Density implications of shift compensation postprocessing in holographic storage systems

Menetrier

Burr

2003

Appl. Opt.

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We investigate the effect of data page misregistration, and its subsequent correction in postprocessing, on the storage density of holographic data storage systems. A numerical simulation is used to obtain the bit-error rate as a function of hologram aperture, page misregistration, pixel fill factors, and Gaussian additive intensity noise. Postprocessing of simulated data pages is performed by a nonlinear pixel shift compensation algorithm [Opt. Lett. 26, 542 (2001)]. The performance of this algorithm is analyzed in the presence of noise by determining the achievable areal density. The impact of inaccurate measurements of page misregistration is also investigated. Results show that the shift-compensation algorithm can provide almost complete immunity to page misregistration, although at some penalty to the baseline areal density offered by a system with zero tolerance to misalignment.

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Section: Review Of the Methodsmentioning

confidence: 99%

Density implications of shift compensation postprocessing in holographic storage systems

Menetrier

Burr

2003

Appl. Opt.

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“…9 The term erasure effects refers to loss of fidelity attributed to the effects of absorption. 10,11 The absorption creates variations in local intensity; thus holograms erase nonuniformly across the crystal volume. This can cause spatial variation in the hologram strength across the image ͑imageplane geometry͒ or a broadened point-spread function ͑Fourier plane geometry͒.…”

Section: Relating the Number Of Stored Holograms And The Raw Bit-erromentioning

confidence: 99%

Experimental evaluation of user capacity in holographic data-storage systems

et al. 1998

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An experimental procedure for determining the relation between the number of stored holograms and the raw bit-error rate (BER) (the BER before error correction) of a holographic storage system is described. Compared with conventional recording schedules that equalize the diffraction efficiency, scheduling of recording exposures to achieve a uniform raw BER is shown to improve capacity. The experimentally obtained capacity versus the raw-BER scaling is used to study the effects of modulation and error-correction coding in holographic storage. The use of coding is shown to increase the number of holograms that can be stored; however, the redundancy associated with coding incurs a capacity cost per hologram. This trade-off is quantified, and an optimal working point for the overall system is identified. This procedure makes it possible to compare, under realistic conditions, system choices whose impact cannot be fully analyzed or simulated. Using LiNbO(3) in the 90 degrees geometry, we implement this capacity-estimation procedure and compare several block-based modulation codes and thresholding techniques on the basis of total user capacity.

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“…This new reference beam can then be used to store an independently accessible page of data. This has been used to store as many as 10,000 pages in the same ' 1cm3 block of material [6].…”

Section: The Holographic Digital Data Channelmentioning

confidence: 99%

“…Change in the readout conditions. This can occur, for instance, when the recording alters the properties of the recording material, causing unwanted changes in the reference beam path between the time the hologram is recorded and the time it is reconstructed [9][10][11]. Often, the reference beam angle or wavelength can be tuned to optimize the diffraction efficiency and partially compensate for this effect [9].…”

Section: The Optical Pathmentioning

confidence: 99%

<title>Optimizing the holographic digital data storage channel</title>

Burr

Ashley

Marcus

et al. 1998

Advanced Optical Memories and Interfaces to Computer Storage

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Holographic storage has the potential to become a digital data storage technology with fast readout and high density. Computer users have come to expect, however, that data retrieved from their storage devices will be retrieved error-free (with a probability of error <10 12). In both conventional storage devices and holographic data storage, achieving this degree of reliability involves a good understanding of the data channel and a combination of careful hardware engineering, signal processing, and coding.At the IBM Almaden Research Center, we have leveraged the expertise acquired with 1-dimensional, timedependent data channels found in magnetic and optical data storage systems, to develop unique and highly effective signal processing and coding algorithms to optimize the performance of the 2-dimensional, space-dependent digital holographic data storage channel. Crucial to our efforts has been the high-performance holographic data storage platform we built in 1996. This tool has allowed us to characterize and perturb a real holographic data channel, and implement and evaluate new data-coding and signal processing algorithms. This rapid feedback loop between ideas, implementation, and results both aids in selecting fruitful approaches and yields deeper understanding of the underlying data channel.In this paper, we discuss the holographic digital data storage channel as divided into five parts: the optical path, pre-processing (how the data gets into the holograms), post-processing (manipulation of raw data just after optical detection), conversion into binary 0's and l's, and error-correction (using added redundancy). Optimizing the channel involves maximizing the system performance (density, speed) while minimizing complexity (and thus cost) and maintaining the required degree of reliability. INTRODUCTIONBy accessing the third dimension of storage media, volume holographic data storage can provide both high density and fast readout [1][2][3] . Thousands of holograms, each containing a page of data, are multiplexed into a common volume and accessed independently by Bragg-matched diffraction. As the size of this common volume is decreased, density (either volumetric or areal) increases. Since each data page can contain as many as a million pixels [4], reading one thousand pages a second results in a data rate of 1 Gbit/second.As with any real-world data transmission or storage system, a holographic storage system is a noisy data channel.

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Absorption effects in photorefractive volume-holographic memory systems I Beam depletion

Cited by 7 publications

References 17 publications

Density implications of shift compensation postprocessing in holographic storage systems

Density implications of shift compensation postprocessing in holographic storage systems

Experimental evaluation of user capacity in holographic data-storage systems

<title>Optimizing the holographic digital data storage channel</title>

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