Non-volatile holographic storage in doubly doped lithium niobate crystals

Buse, K.; Adibi, Ali; Psaltis, Demetri

doi:10.1038/31429

Cited by 490 publications

(259 citation statements)

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“…More recently, there has been increasing interest in epitaxially grown BaTiO 3 thin films for optical waveguide modulators [3]. The EO effect is the origin of the photorefractive effect, exploited in non-volatile holographic data storage in LiNbO 3 [4]. It was also used to probe locally the ferroelectricity in SrTiO 3 films [5].…”

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First-Principles Study of the Electro-Optic Effect in Ferroelectric Oxides

2004

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We first present a method to compute the electrooptic tensor from first principles, explicitly taking into account the electronic, ionic and piezoelectric contributions. We then study the non-linear optic behavior of three paradigmatic ferroelectric oxides. Our calculations reveal the dominant contribution of the soft mode to the electrooptic coefficients in LiNbO3 and BaTiO3 and its minor role in PbTiO3. We identify the coupling between the electric field and the polar atomic displacements along the B-O chains as the origin of the large electrooptic response in perovskite ABO3 compounds. Finding better EO materials is a desirable goal. However, the experimental characterization of optical nonlinearities requires high-quality single crystals that are not always directly accessible nor easy to make. Input from accurate theoretical calculations allowing to predict the non-linear optical behavior of crystalline solids would therefore be particularly useful.For many years, theoretical investigations of non-linear optical phenomena were restricted to semi-empirical approaches such as shell models [6] or bond-charge models [7,8]. In the last decade, significant theoretical advances have been reported concerning first-principles density functional theory (DFT) calculations of the behavior of periodic systems in an external electric field [9,10] and opened the way to direct predictions of various optical phenomena. Recently, particular attention has been paid to the calculation of non-linear optical (NLO) susceptibilities and Raman cross sections [11,12].In this Letter, we go one step further and present a method to predict the linear EO coefficients of periodic solids within DFT. Our method is very general, and can be applied to paradigmatic ferroelectric oxides : LiNbO 3 , BaTiO 3 and PbTiO 3 . We find that first-principles calculations are fully predictive, and provide significant new insights into the microscopic origin of the EO effect. In particular, we highlight the predominent role of the soft mode in the EO coupling of LiNbO 3 and BaTiO 3 , in contrast with its minor role in PbTiO 3 .At linear order, the dependence of the optical dielectric tensor ε ij on the static (or low-frequency) electric field E γ is described by the linear EO tensor r ijγ :Throughout this paper, we follow the convention of using Greek and Roman indexes (resp.) to label static and optical fields (resp.). We write all vector and tensor components in the system of cartesian coodinates defined by the principal axes of the crystal under zero field. We also refer to the atomic displacements τ κα [κ labels an atom and α a cartesian direction] within the basis defined by the zone-center transverse optic (TO) phonon eigendisplacements u m (κα):Let us first consider the clamped (zero strain) EO tensor, r η ijγ , in which all electric-field induced macroscopic strains η are forbidden. This is achieved experimentally by working at a frequency sufficiently high to avoid strain relaxations but low compared to the frequency of the TO modes. Within the ...

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First-Principles Study of the Electro-Optic Effect in Ferroelectric Oxides

2004

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“…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.…”

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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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“…The basic approach to be employed for this makes use of a holographic video disk, which is discussed in detail in reference 22. Since the query clips have to be periodically refreshed, based on the event of interest, one can make use of a rewritable memory, namely a lithium niobate crystal 34,35 . During the operation of the AER system, the data read from the crystal will be made co-linear with the data read from the holographic video disc using a 50/50 beam splitter, as illustrated in figure 14.…”

Section: Implementing Aer Employing a Vapor Cell A Holographic Videomentioning

confidence: 99%

All optical three dimensional spatio-temporal correlator for automatic event recognition using a multiphoton atomic system

Monjur

Fouda

Shahriar

2016

Optics Communications

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We describe an automatic event recognition (AER) system based on a three-dimensional spatio-temporal correlator (STC) that combines the techniques of holographic correlation and photon echo based temporal pattern recognition. The STC is shift invariant in space and time. It can be used to recognize rapidly an event (e.g., a short video clip) that may be present in a large video file, and determine the temporal location of the event. Using polar Mellin transform, it is possible to realize an STC that is also scale and rotation invariant spatially. Numerical simulation results of such a system are presented using quantum mechanical equations of evolution. For this simulation we have used the model of an idealized, decay-free two level system of atoms with an inhomogeneous broadening that is larger than the inverse of the temporal resolution of the data stream. We show how such a system can be realized by using a lambda-type three level system in atomic vapor, via adiabatic elimination of the intermediate state. We have also developed analytically a three dimensional transfer function of the system, and shown that it agrees closely with the results obtained via explicit simulation of the atomic response. The analytical transfer function can be used to determine the response of an STC very rapidly. In addition to the correlation signal, other nonlinear terms appear in the explicit numerical model. These terms are also verified by the analytical model. We describe how the AER can be operated in a manner such that the correlation signal remains unaffected by the additional nonlinear terms. We also show how such a practical STC can be realized using a combination of a porous-glass based Rb vapor cell, a holographic video disc, and a lithium niobate crystal.

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Non-volatile holographic storage in doubly doped lithium niobate crystals

Cited by 490 publications

References 17 publications

First-Principles Study of the Electro-Optic Effect in Ferroelectric Oxides

First-Principles Study of the Electro-Optic Effect in Ferroelectric Oxides

Effect of annealing in two-center holographic recording

All optical three dimensional spatio-temporal correlator for automatic event recognition using a multiphoton atomic system

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