Sensitivity improvement in two-center holographic recording

Adibi, Ali; Buse, K.

doi:10.1364/ol.25.000539

Cited by 75 publications

(37 citation statements)

References 6 publications

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“…The sensitivity in a two-center holographic re- cording has already been discussed in another publication. 39 We showed in Ref. 39 that we can improve the sensitivity of two-center recording by a factor of 20 if we use green light instead of red light for recording.…”

Section: Discussionmentioning

confidence: 99%

Two-center holographic recording

2001

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We describe a two-center holographic recording method for the storage of persistent holograms in doubly doped lithium niobate crystals. We use a two-center model, and we show that our experimental observations can be explained by the model. We describe experimental methods for finding the unknown material parameters of LiNbO 3 :Fe:Mn crystals for the two-center model, and we discuss the optimization of two-center recording.

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Section: Discussionmentioning

confidence: 99%

Two-center holographic recording

2001

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“…3a were calculated without considering persistence. If we are interested in the persistent sensitivity, we need to modify this value by the partial erasure of the hologram during readout, as explained in [9]. This results in even lower values of sensitivity, especially around the specific value of µ that gives zero M/#.…”

Section: Effect Of Carrier Mobility In Two-center Holographic Recordingmentioning

confidence: 99%

“…More recently, two-center holographic recording was proposed and demonstrated [7,8]. Two-center recording makes storage of persistent holograms possible without sacrificing the dynamic range and sensitivity considerably [9]. The sensitivity of the widely used congruently melting LiNbO 3 crystals, however, is still not very * Corresponding author.…”

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The role of carrier mobility in holographic recording in LiNbO3

Adibi

Buse

2001

Appl Phys B

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Abstract.We investigate the role of carrier mobility in holographic recording in LiNbO 3 crystals. Both normal holographic recording (single wavelength, single trap) and twocenter recording are considered, and the differences between the performances of the two methods are explained. We show that increasing mobility by using stoichiometric crystals or by doping with Mg does not improve sensitivity considerably, but does reduce M/# by at least one order of magnitude. 42.40.Pa; 42.40.Ht Volume holographic storage systems are tried and tested with photorefractive crystals as the recording medium [1]. In such systems, the inhomogeneous illumination created by the interference of the reference and signal beams excites charge carriers from impurity levels into the conduction or valence bands, the charge carriers migrate and they are trapped by empty impurities elsewhere. A space-charge field builds up and modulates the refractive index via the electro-optic effect. PACS:The important material properties are sensitivity (S), dynamic range (M/#) and persistence (or non-destructive readout). For several years, lack of persistence was the major drawback of holographic storage in photorefractive crystals, and several methods (thermal fixing [2], electrical fixing [3], two-photon recording [4], frequency-difference holograms [5] and readout with wavevector spectra [6] ) were proposed to solve this problem. More recently, two-center holographic recording was proposed and demonstrated [7,8]. Two-center recording makes storage of persistent holograms possible without sacrificing the dynamic range and sensitivity considerably [9]. The sensitivity of the widely used congruently melting LiNbO 3 crystals, however, is still not very * Corresponding author.(Fax: +1-404/894-4641, E-mail: adibi@ece.gatech.edu) good. Therefore, the main challenge in holographic storage in LiNbO 3 crystals is the improvement of the sensitivity.Sensitivity is a measure of recording speed. It is defined as the initial recording slope of the square root of the diffraction efficiency normalized to recording intensity and material thickness. Recording and erasure time constants in holographic recording are approximately inversely proportional to the mobility of the carriers responsible for recording (i.e., electrons in the conduction band or holes in the valence band). Holograms can be recorded faster if we increase the mobility of carriers responsible for recording. Therefore, one idea for increasing sensitivity could be to increase the carrier mobility. In almost all holographic recording experiments in LiNbO 3 , these carriers are electrons in the conduction band. It is suggested that the mobility of these electrons (µ) can be varied by changing the stoichiometry of LiNbO 3 : congruently melting LiNbO 3 crystals (typical ratio of Li to Nb about 94%) have a lower electron mobility than perfectly stoichiometric crystals (ratio of Li to Nb equal to 1). It is also suggested that the mobility of electrons in the conduction band of LiNbO 3 can be varied by ...

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“…We recently proposed and demonstrated the two-center holographic recording method to solve this problem by using doubly-doped LiNbO 3 . 4,5 Several aspects of persistent holographic storage in doubly-doped LiNbO 3 ͑i.e., hologram multiplexing, 6 sensitivity improvement, 7 optimization, 5,8 and the role of different dopants 9 -11 ͒ were investigated. In this paper we present a framework for the comparison of the performances of singly-doped and doubly-doped LiNbO 3 crystals for holographic storage.…”

Section: Introductionmentioning

confidence: 99%