A video rate operation (30 Hz) with more than 80% diffraction efficiency and net gain of 89 cm–1 was reported in a photorefractive (PR) composite based on poly((4-diphenylamino)benzyl acrylate) ...(PDAA). A diffraction efficiency of 60% was attained at 60 Hz. To reveal the mechanism behind such high-performance, transient photocurrent measurements were performed. The investigation clearly showed the importance of the (4-(diphenylamino)phenyl)methanol (TPAOH) plasticizer in the charge transport process of the PR composite. The function of TPAOH was demonstrated as a normal plasticizer, as well as an effective photoconductivity enhancement factor of the composite. The analysis of the shapes of the transient photocurrent curve with two trapping sites revealed that TPAOH strongly assisted charge transport in PDAA. The response time of the PR composite was improved by increasing the TPAOH concentration and suppressing the shallow trapping effect. In contrast, the reference 2,4,6-trimethyl-N,N-diphenylaniline (TAA) plasticizer was found to significantly suppress the photocurrent (up to 100 times) compared to that of the TPAOH samples. The replacement of TPAOH by TAA degraded the response time of the diffraction beam. This was attributed to the low-scattering effect caused by the TAA. The study revealed that the deep and shallow traps originate from the PDAA polymer.
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IJS, KILJ, NUK, PNG, UL, UM
Photochromic effect in nominally pure and doped Sn2P2S6 photorefractive crystals is investigated in the temperature range 120–310K. This effect determines a mechanism of the amplitude hologram ...formation at low temperatures, and we show that a competition between the photorefractive (phase) and the amplitude gratings occurs at increasing temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The nonlinear optical properties of Ge 10 Se 90-x Te x (x = 0,10, 20, 30, 40, 50) thin films have been investigated as a function of composition and substrate deposition temperatures (303, 363, and ...423 K). The third-order nonlinear susceptibility and nonlinear refractive index have been estimated. Nonlinearity in refractive index increases with Te content and also with increasing substrate temperature. Among the investigated compositions of Ge 10 Se 90-x Te x , the Ge 10 Se 40 Te 50 composition shows more prominent nonlinear refractive index in comparison with pure silica. The high third-order susceptibility and nonlinear refractive index may make these materials capable for high-speed communication fibers.
We present a new type of LC cell with a gold nano-island film deposited on one of electrodes. A nematic LC layer (a mixture E7) is 20.7 μm-thick. Nonlinear optical characteristics were measured in ...dependence on a low dc voltage (0.096-0.59 V/μm) and for two angle of the cell rotation:
and
Our cell exhibits excellent nonlinear properties, namely, high diffraction efficiency, strong energy transfer, low switching voltage, its nonlinear refractive index
cm
2
/W and susceptibility
esu. The first-order diffraction efficiency achieves the maximum (more 10%) at 0.24 V/μm. Exclusion is a long self-erasure time - the most fast time (a few second) is observed at 0.096 V/μm. We believe it should be decreased with the decrease of LC thickness.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Hot-electron transport in photorefractive semiconductors strongly affects the recording of photorefractive grating. However, the theoretical description of this behavior has been always made under ...small signal approximation. In this paper rigorous numerical investigation of stationary and transient behavior of photorefractive grating induced in the semiconductor quantum wells structure is presented. The calculations were performed in the framework of the band transport model for the case of high modulation depth. The comparison between numerical and approximated analytical solutions is given as well as between linear and nonlinear transport model. Obtained results allow to verify some statement formulated in few earlier works concerning beneficial effects of electron transport nonlinearity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The kinetic dependence of the photorefractive effect in the congruent lithium niobate crystal is determined in the work. The adequacy of the model for calculating the photoelectric fields from the ...indicatrix of photoinduced light scattering is shown. Two methods for determining the induced birefringence by interferograms and on the parameters of photoinduced light scattering are compared.
•The photorefractive birefringence was investigated by a phase interrogation.•The probing beam with focused and phase modulated was adopted.•The method was used to study the different orientations in ...electro-optic crystals.
A single-beam pump-probe method based on a dual-channel phase measurement system was adopted to measure photo-induced phase variations caused by the photorefractive effect. This study systematically studied the dependence of photorefractive birefringence on the propagation directions of probing lights in various electro-optic crystals at visible wavelengths.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Double-doping technology for growing lithium niobate crystals (LiNbO
3
:Mg:Zn) was developed. The crystals were highly homogeneous and had high optical damage resistance, so they show promise for use ...as photonic and nonlinear optical components. The crystals were grown from the LiNbO
3
:0.145 wt % Mg:1.98 wt % Zn batch. The batch was prepared by homogeneous doping. The proposed flowsheet can serve as the basis for a large-scale technology of doped lithium niobate single crystals.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
An adaptive spatial filter is used as an optical novelty filter to detect photothermal mirror (PM) signals in high absorbing materials using continuous wave laser excitation. The optical novelty ...filter uses an optical beam-fanning limiter based on single domain barium titanate (BaTiO3), cut and poled 45° relative to the c-axis. The optical novelty filter approach relaxes the requirement for high sample surface smoothness because the effect aperture adapts to the surface, reducing the stationary background from the optical signal and provides a means of developing the photothermal mirror signal. Time-dependent probe laser phase shifts due to photothermal surface deformation pass through the optical novelty filter and are detected as an intensity increase over the stationary or “mundane” signal. Experimental studies are performed using four well-characterized metals using both the conventional photothermal mirror and optical novelty filter apparatuses in order to understand the complicated signal behavior. Signal behavior is analyzed in different excitation intervals using pseudo-chopped sample excitation with different duty cycles. Optical novelty filter signals show fast response for changes in the spatial beam profile followed by long relaxation time. Reasons for the optical novelty filter response are described.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Holographic interferometry methods, based on mixing of a stationary reference light beam and a phase-modulated signal beam at the related perturbations of the dielectric tensor in photosensitive ...crystals, have been applied to measure material parameters determining the value of these perturbations. Experimental conditions, under which one can distinguish contributions to the mixing from the flexoelectric and electrogyration effects in cubic photorefractive sillenite crystals, are determined, and the necessity of taking into account the contribution from the flexogyration effect is demonstrated.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
