System metric for holographic memory systems

Mok, Fai; Burr, Geoffrey W.; Psaltis, Demetri

doi:10.1364/ol.21.000896

Cited by 292 publications

(126 citation statements)

References 2 publications

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“…Therefore, reducing the crystal results in an increase in both sensitivity and the M/#. 9 This explains the recording and readout curves for both LN2 and LN3. Since LN3 is more reduced than LN2, it has faster recording and stronger final diffraction efficiency.…”

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confidence: 92%

Effect of annealing in two-center holographic recording

Adibi

Buse

1999

Applied Physics Letters

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Persistent holograms are recorded with red light in lithium niobate crystals doped with manganese and iron. We find that the oxidation/reduction state of the crystal has a profound impact on the recording and readout performance. The underlying physical processes are investigated and the recording and readout responses are explained and optimized. © 1999 American Institute of Physics. ͓S0003-6951͑99͒05325-5͔Photorefractive materials are the best reversible storage materials known so far and several holographic storage demonstrators using iron-doped photorefractive lithium niobate (LiNbO 3 :Fe) were presented in the last few years. 1-3 However, erasure of the holograms during readout has been one of the major problems in the practical realization of holographic read/write memories. We recently proposed a method to solve this problem by using doubly doped LiNbO 3 . 4 In this letter, we explain the effects of annealing the crystal on the performance of the recently proposed twocenter recording method.In the recent work, 4 LiNbO 3 doped with manganese ͑Mn͒ and iron ͑Fe͒ was used. The energy band diagram of such a crystal is shown in Fig. 1. Fe and Mn ions occur in the valence states Mn 2ϩ/3ϩ and Fe 2ϩ/3ϩ , 5 and thermal depletion plays no role in room temperature. Electrons can be excited by ultraviolet light either from Mn 2ϩ or from Fe 2ϩ into the conduction band while red light excites electrons only from the shallower Fe 2ϩ . The conduction-band electrons can recombine with both centers, and thus, ultraviolet illumination populates the Fe 2ϩ/3ϩ level partially while red light illumination empties the Fe sites. The filled Fe levels cause a broad-band absorption in the visible with a maximum at a 477 nm wavelength. 6 Thus, ultraviolet light sensitizes the material while red light bleaches it. The basic idea of twocenter holographic recording is to bring with the ultraviolet light electrons from Mn to Fe via the conduction band, use these electrons to record the hologram with red light, and eventually transfer the electrons from iron back to the manganese centers by red light. This results in a hologram stored in Mn centers that persists against further red illumination.One of the key material parameters in two-center holographic recording is the initial electron concentration in Mn and Fe traps. These concentrations can be varied by an annealing treatment. 7 Since Mn traps are deeper in the band gap than Fe traps, electrons would fill the Mn traps before Fe traps when the crystal is reduced. For persistent holographic recording, it is necessary that the final hologram be stored in Mn centers. Therefore, it is essential that at the end of the annealing process all Fe traps be empty, and only a portion of the Mn traps be filled. To investigate the effect of the oxidation/reduction state of the crystal we performed experiments with four x-cut congruent LiNbO 3 crystals doped with 0.075 wt % Fe 2 O 3 and with 0.01 wt % MnO. The crystals were all from the same boule. The samples were strongly oxidized ͑LN1͒, oxidized ͑...

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confidence: 92%

Effect of annealing in two-center holographic recording

Adibi

Buse

1999

Applied Physics Letters

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“…The sensitivity factor of the material has been determined at two different wavelengths (532 and 407 nm). Multiplexing feature of the storage material is usually represented by the M# [6], a property dependent on both writing and erasure dynamics. We carried out several experiments in order to determine it.…”

Section: Photoaddressable Polymers [I]mentioning

confidence: 99%

“…This number characterizes the material and the applied experimental arrangement. There are two ways to determine it [6]. The first method is to make a large number of multiplexing (M) with a proper exposure schedule that results in equal hologram efficiencies.…”

Section: V344 Multiplexing Ability: M#mentioning

confidence: 99%

Dynamic behavior of azobenzene polyester used for holographic data storage

et al. 2001

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Dynamic behavior of thin photoaddressable polyester films was studied. The saturation process due to Fourier holographic recording was investigated. Model experiments show an optimal intensity ratio of the object and reference beams, where the highest efficiency occurs. This ratio is inversely proportional to the reference intensity. The material has a significantly higher sensitivity at 407 nm than at 532 nm. For 1 pm thick sample an M# of 0.25 was measurable.

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“…In a holographic memory, a page of data is recorded as phase gratings by interference between the spatial modulated signal beam and a coherent reference beam inside a photorefractive crystal such as LiNb0 3 Figure 1. Different pages of data are angle multiplexed by a laser diode (LD) array.…”

Section: A Holographic Memory Systemmentioning

confidence: 99%

“…3 With M holograms recorded with exponential schedule to keep each hologram the same intensity, the diffraction efficiency of each hologram would be:…”

Section: Cost Modelmentioning

confidence: 99%

Optoelectronic Memory Interface

Psaltis

1999

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System metric for holographic memory systems

Cited by 292 publications

References 2 publications

Effect of annealing in two-center holographic recording

Effect of annealing in two-center holographic recording

Dynamic behavior of azobenzene polyester used for holographic data storage

Optoelectronic Memory Interface

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