Photorefraction and self-enhancement of holograms in LiNbO3 and LiTaO3 crystals

Shvarts, K.K.; Ozols, Andris; Augustov, P. A.; Reinfelde, M.

doi:10.1080/00150198708008225

Cited by 12 publications

(10 citation statements)

References 23 publications

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“…It has been used by us to determine the transport characteristics and polar axis direction of LiNbO 3 :Fe crystals, disorder correlation length in an amorphous semiconductors, etc. [2] [4] [10]. SE effect of holograms in azobenzene derivatives is rarely studied.…”

Section: Introductionmentioning

confidence: 99%

Self-Enhancement of Scalar and Vector Holographic Gratings in Azobenzene Molecular Glassy Films

Ozols¹,

Kokars²,

Augustovs³

et al. 2014

OPJ

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Self-enhancement (SE) effect of scalar and vector holographic gratings (HG) recorded in three different azobenzene molecular glassy films is experimentally studied in both transmission and reflection modes at 532 and 633 nm. The maximal SE factor (the ratio of diffraction efficiency to its initial value) SEF = 42 has been achieved. It is shown that the model of complementary HG can be applied also in scalar transmission thin HG case to explain coherent SE. The possibility of vector HG coherent SE in transmission mode is experimentally demonstrated for the first time (SEF = 4.3). The possibility of coherent HG SE in reflection mode is also established for the first time (SEF = 21). HG recording processes as well as coherent SE processes are found to be independent in transmission and reflection modes being determined by volume and surface relief HG, respectively. The permittivity gradient mechanism is proposed to explain the coherent SE of surface relief HG. Both HG recording and coherent SE efficiencies strongly decrease when HG period is decreased from 2 µm to 0.5 µm. No relaxational SE effect is found. Coherent SE effect in molecular glasses is found to be weaker than in inorganic materials.

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Section: Introductionmentioning

confidence: 99%

Self-Enhancement of Scalar and Vector Holographic Gratings in Azobenzene Molecular Glassy Films

Ozols¹,

Kokars²,

Augustovs³

et al. 2014

OPJ

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“…It has been used by us to determine the transport characteristics and polar axis direction of LiNbO 3 :Fe crystals, disorder correlation length in an amorphous semiconductor, etc. [2,13]. SE of HG has also been reported in Bi 12 Ti 0.76 V 0.24 O 20 crystals [14] and dichromated poly(vinylalcohol) films [15].…”

Section: Introductionmentioning

confidence: 70%

“…The intensities of these diffracted beams are varying in time and the complementary HG is phase-shifted by π/2 with respect to initial HG [3,13]. In this paper we shall take the simplest approach neglecting the contribution of the initial HG to the summary HG and considering only the initial CSE stage.…”

Section: Resultsmentioning

confidence: 99%

“…It should be noted that if sensitivity is defined as in the two-beam case (i. e. if we take S 1 /M instead of S 1 ) then it also decreases with growing M. In terms of Eqs. (7,8,9,13) with M = M CSE one can assume that quantities γ max , γ min and τ acquire the dependence on M due to RSC.…”

Section: Resultsmentioning

confidence: 99%

“…Photosensitivity of these films depends on light intensity [17]. The existence of minimum visibility for the recording light intensity interference pattern could explain the fact that CSE is not observed in all materials as can be expected from the CSE complementary HG model [3,13] even when the holographic recording itself is efficient (Table 1). We have chosen an a-As 2 S 3 film for these experiments because the CSE effect is the most efficient in these films.…”

Section: Introductionmentioning

confidence: 99%

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Recording of holographic gratings and their coherent self-enhancement in an a-As<sub>2</sub>S<sub>3</sub> film with a minimum light intensity modulation

Ozols¹,

Augustovs²,

Saharov³

2012

Lith. J. Phys.

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The holographic grating recording efficiency and the coherent self-enhancement efficiency of gratings are experimentally studied depending on the recording light interference fringe visibility in an a-As 2 S 3 chalcogenide film in order to find the minimum visibility. The minimum fringe visibility M min = 3.6×10 -4 is found, which is determined by the scattered light background. In this case the maximal diffraction efficiency η max = 0.05% and the maximal self-enhancement factor ξ max = 5.0, compared to η max = 15% and ξ max = 12.3 in the optimal M = 1.0000 case. In the case of two-beam holographic grating recording the maximal diffraction efficiency increases when M is increased, whereas sensitivity decreases. A simple model, based on linear recording with the spatial light intensity distribution governed by M and including intensity-dependent material photosensitivity and grating relaxation, is proposed to explain these results. In the case of coherent self-enhancement both the maximal diffraction efficiency and sensitivity increase with fringe visibility M. This can be explained by the fact that mechanical stress modulation during the initial grating recording depending on M is followed by relaxational structural changes reinforcing the coherent self-enhancement effect. The developed approach may explain the absence of this effect in some azobenzene oligomer films.

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