Photorefractive centers in LiNbO3, studied by optical-, Mössbauer- and EPR-methods

Kurz, H.; Krätzia, E.; Keune, W.; Engelmann, H.; Gonser, U.; Dischler, B.; Räuber, A.

doi:10.1007/bf00886038

Cited by 272 publications

(92 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…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.…”

mentioning

confidence: 99%

Effect of annealing in two-center holographic recording

Adibi

Buse

1999

Applied Physics Letters

View full text Add to dashboard Cite

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 ͑...

show abstract

mentioning

confidence: 99%

Effect of annealing in two-center holographic recording

Adibi

Buse

1999

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…4. The K␤ line is split into a main intense emission line K␤ 1,3 , which reflects 3p-1s spin down transitions and a satellite K␤Ј on the low energy site, which reflects 3p-1s spin-up transitions. The spin selectivity of the K␤ emission line has been explained with the exchange interaction between the unpaired spin-up electrons in the 3d state and the net 3p electron spin after transition of a 3p electron to the 1s state.…”

Section: Hrxe Spectra and Rixs Mapmentioning

confidence: 99%

“…In the case of Fe-doped LN crystals the iron atoms are found in the valence states Fe 2+ and Fe 3+ . 3 Upon inhomogeneous illumination, the electrons from the Fe 2+ impurity centers are excited into the conduction band. They migrate due to drift, diffusion, and bulk photovoltaic effects, 4 and they are finally trapped by Fe 3+ centers preferentially in the dark areas.…”

Section: Introductionmentioning

confidence: 99%

Site-selective investigation of site symmetry and site occupation of iron in Fe-doped lithium niobate crystals

Vitova

Hormes

Falk

et al. 2009

Journal of Applied Physics

View full text Add to dashboard Cite

Lithium niobate ͑LN͒ crystals, in particular after strong oxidation, are of great relevance for applications in photorefraction and nonlinear optics. Crystals doped with 2 or 4 wt % of iron are studied by extended x-ray absorption fine structure spectroscopy. The Fe atoms are observed to be sixfold coordinated by oxygen atoms and incorporated into the Li site. No evidence for formation of iron oxide clusters is found. In situ x-ray absorption spectroscopy measurements of the thermoelectric oxidation of a LN:Fe 2 wt % crystal and the analyses of the partially site-selective x-ray absorption near edge structure spectra of a LN:Fe 4 wt % crystal provide site-selective structural information. We found that the Fe 2+ and Fe 3+ sites have the same site symmetries and positions in the LN matrix, i.e., the Fe 2+ and Fe 3+ atoms are both octahedrally coordinated by six oxygen atoms and both occupy the Li site.

show abstract

“…Absorption of blue or green light excites electrons from Fe 2ϩ to the conduction band, generating Fe 3ϩ . 8 Furthermore, there is a crystal-field splitting of the Fe 2ϩ level, adding a new energy level denoted (Fe 2ϩ )*. 8 The excitation Fe 2ϩ →(Fe 2ϩ )* takes place at about 1200 nm.…”

Section: Absorption Mechanisms In Linbo 3 :Fementioning

confidence: 99%

“…8 Furthermore, there is a crystal-field splitting of the Fe 2ϩ level, adding a new energy level denoted (Fe 2ϩ )*. 8 The excitation Fe 2ϩ →(Fe 2ϩ )* takes place at about 1200 nm. In addition, LiNbO 3 shows fundamental band-to-band absorption at short wavelengths, starting with a weak tail at about 600 nm, and becoming strong below 400 nm.…”

Section: Absorption Mechanisms In Linbo 3 :Fementioning

confidence: 99%

Temperature dependence of absorption in photorefractive iron-doped lithium niobate crystals

Panotopoulos

Luennemann

Buse

2002

Journal of Applied Physics

View full text Add to dashboard Cite

We present experimental data showing a significant dependence of light absorption on temperature in photorefractive LiNbO 3 :Fe crystals. The results are successfully explained by assuming that the widths of the Fe 2ϩ absorption bands in the visible and in the infrared spectral region depend on temperature. The findings are of relevance for thermal fixing of holograms. Furthermore, a temperature-induced increase of the infrared absorption is promising for improved infrared recording.

show abstract

Photorefractive centers in LiNbO3, studied by optical-, Mössbauer- and EPR-methods

Cited by 272 publications

References 25 publications

Effect of annealing in two-center holographic recording

Effect of annealing in two-center holographic recording

Site-selective investigation of site symmetry and site occupation of iron in Fe-doped lithium niobate crystals

Temperature dependence of absorption in photorefractive iron-doped lithium niobate crystals

Contact Info

Product

Resources

About