bluuebunny/crossref_metadata_2025 huggingface dataset:
Observation and Study of the Photorefractive Effect in Doped Nonlinear Polymers
Authors: Burland D. M. , Ducharme S , Moerner W. E. , Scott J. C. , Walsh C. A.
Published: February 2023

Many applications of photorefractivity have been proposed: a virtually unlimited array of image processing techniques including phase conjugation and novelty filtering, simulations of neural networks and associative memories, and high density efficient holographic optical storage. Until very recently, all materials showing the photorefractive effect have been inorganic crystals1. A problem currently impeding the wide-spread exploitation of the photorefractive effect has been the fact that inorganic materials exhibiting the effect tend to be difficult and thus expensive to prepare and, because of their crystalline nature, to be incompatible with current integrated packaging processes. There is thus a continuing and critical need for new classes of photorefractive materials with improved processability and performance.
Characterization of a New Photorefractive Material:K1-yLyT1-xNx
Authors: Agranat Aharon , Hofmeister Rudy , Leyva Victor , Yariv Amnon
Published: February 2023

The use of photorefractive materials to store volume holograms for optical computing and optical memories has long been an active area of research1. In addition, these materials have been considered in the implementation of optical neural networks.
The New Type of KNSBN: Cu Crystal as High-performance Self-Pumped Phase-Conjugator
Authors: Guangyin Zhang , Jingjun Xu , Simin Liu , Yuanqing Wu , Yongyuan Song , Huanchu Chen
Published: February 2023

In KNSBN several crystallographic sites can be partially empty , which allow crystal composition to be tailored. The magnitude of longitudinal (r51) and transverse (r33) electro-optic coefficient depend greatly on the ratios of Ba/Na and K/Na. So either r33 or r51 can be made large, absorption and response wave range can be controlled in the desired spectral range by changing the dopant and its concentration . Accoding to these the crystal with partially- filled composition Cu -doped (K0.5Na0.5)0.2 (Sr0.1Ba0.39)0.9 Nb2O6 is grown.
The Photorefractive Properties of Quantum-Confined Excitons
Authors: Nolte D. D. , Melloch M. R.
Published: February 2023

Multiple-quantum-well structures in semiconductors have strong spatial inhomogeneity. Bandgaps in these multilayer samples vary by several tenths of eV over monolayer distances. These dramatic spatial changes in bandstructure have significant consequences for the photorefractive effect, creating new effects that have no analog in bulk photorefractive materials. The ability to design new materials and devices, and control desired photorefractive properties, has few limitations. Several processes give photorefractive quantum well structures unique advantages. Two charge separation processes, in particular, contribute to the novel effects: 1) bandgap energies can be selectively tuned to isolate optical absorption to some layers, but not others; 2) carriers in quantum wells tunnel into barrier regions with larger bandgaps, generating metastable defect occupancies with associated electric fields. These processes couple with one of the strongest advantages of quantum well structures: quantum-confined excitons. Quantum-confined excitons in semiconductors exhibit large quadratic electro-optic effects. The quadratic electro-optic effect combines with the charge separation processes to yield ultra-high sensitivity photorefractive effects with large diffraction efficiencies[1] and beam coupling gains. In this paper, we present the theory of photorefractive effects in quantum well structures, concentrating on the role of spatial inhomogeneity in the nonlinear optical behavior.
Red-green diffraction instability in the photorefractive mixed crystal Bi12Ti0.76V0.24O20
Authors: Kukhtarev N. V. , Gnatovskii A. , Yanchuk Z. , Semenets T. , Pryadko L. , Kargin Y. , Ringhofer K. H.
Published: February 2023

We have investigated the new doubly color sensitive photorefractive crystal Bi12Ti0.76V0.24O20 by writing a hologram in green (λ = 0.51 µm, cw-argon laser) and reading it out in red (λ = 0.63 µm, cw-HeNe laser). It was found that the diffraction efficiency for the red beam is chaotically oscillating in time with a period of about 0.1 s between zero and some maximum. The diffraction efficiency for the red beam decayed smoothly after the green beam was switched off. These oscillations exist also for values of the diffraction efficiency as low as 0.1%, and therefore can not be explained by overmodulation of the refractive-index grating.
Four-Wave Mixing Steady-State Solutions Utilising the Underlying SU(2) Group Symmetry
Authors: Fish D. , Powell A. K. , Hall T. J.
Published: February 2023

A method of solution for the scalar four wave mixing equations has been known for many years [1]. We show that these equations have an underlying symmetry in the form of the SU(2) group. This formulation identifies the conserved quantities of four wave mixing in an obvious sense rather than in the ad-hoc fashion used previously. The method also solves the equations in terms of beam amplitudes rather than beam ratios.
Electron-Hole Competition in InP:Fe -- The Role of Multiple Defects
Authors: Rana R. S. , Nolte D. D.
Published: February 2023

The photorefractive effect has now been identified and studied in many semi-insulating III-V compound semiconductors [1]. In general, it can be well described by a Single Defect Model (SDM) with one or two types of charge carriers. However, discrepancies arise between theory and the experimental results due to the presence of additional defects. In understanding the role of multiple deep defects in the photorefractive effect, temperature plays a key role. Each different defect has a specific energy position within the bandgap of the material. Thermal emission of carriers trapped at defect sites is a strong (exponential) function of defect energy and the sample temperature. The thermal relaxation of nonequilibrium defect occupancies, and the subsequent effect on the photorefractive effect, can be studied by monitoring the two-wave mixing (2WM) gain and four-wave mixing (4WM) diffraction efficiency as functions of temperature, providing a natural tool to characterize the material. We find that multiple defect levels in InP:Fe lead to dramatic changes in the photorefractive behavior. Reduced gain reported at room temperature can be shown to arise from an additional defect in InP other than isolated Fe.
Origins of the Photorefractive Phase Shift
Authors: Cudney R. S. , Bacher G. D. , Pierce R. M. , Feinberg Jack
Published: February 2023

There is a spatial phase shift between a sinusoidal light intensity pattern and the resulting refractive index grating formed in a photorefractive crystal. For crystals where diffusion is the dominant mechanism for charge migration, this spatial shift is 1/4 of the grating spacing. Any deviation from this value implies some other transport mechanism, such as an applied or internally developed electric field, or the photogalvanic effect, in which optically excited charges preferentially move in one direction in the crystal. Due to its relevance to beam coupling, this spatial shift has been studied extensively using a variety of methods, most of them interferometric in nature1-5. However, interferometric methods only reveal the phase of the complex beam coupling coefficient, which is not necessarily the spatial phase shift of the electro-optically induced grating. Other effects, such as trap grating coupling, can affect the phase of the total coupling coefficient, and thereby prevent a measurement of the spatial phase shift.
Real-Time Optical Intensity Correlator using Photorefractive BSO and a Liquid Crystal Television
Authors: Soutar C. , Wang Z.Q. , Cartwright C.M. , Gillespie W.A.
Published: February 2023

The use of photorefractive Bi12SiO20 (BSO) as a dynamic holographic medium in optical processing systems has been the subject of much activity. Typical operations carried out include edge enhancement [1], novelty filtering [2] and the correlation of optical signals [3]. However the use of BSO in coherent correlator systems is hindered by positional problems [3,4] as the crystal must be inserted at the Fourier plane of the transforming lens(es) to a high degree of accuracy (to within 0.5 % of the focal length of the lens as determined in ref 3).
Multiplicative to Additive Speckle Noise Conversion via Phase Cancellation with Photorefractive Phase Conjugators
Authors: Khoury J. A. , Biernacki A. M. , Woods Charles L. , Cronin-Golomb M.
Published: February 2023

A new technique for dealing with multiplicative complex speckle noise on coherently imaged amplitude objects is presented. This technique uses phase cancellation via quadratic nonlinearity to convert the multiplicative noise into additive noise on the Fourier spectrum. This is accomplished using a noisy image as the pump and a clean planar reference beam as the probe in a degenerate four-wave mixing phase conjugator. The counterpropagating pump is provided by the phase conjugate of the noisy image from a total internal reflection self-pumped phase conjugator whose input is the noisy image transmitted through the first crystal. The phase conjugate output is read off from the clean probe; the remaining noise on the Fourier spectrum of the output image is additive and can be removed by nonlinear filtering in the Fourier plane [1].
Laser-Induced Interference Filters in Photorefractive Materials
Authors: Petersen P.M. , Johansen P.M. , Skettrup T.
Published: February 2023

We investigate the properties of a laser-induced interference filter in photorefractive BaTiO3. The filter has several control parameters for the reflectance and its high wavelength selectivity makes the filter suited as output mirror of a tuneable single mode infrared semiconductor laser. Furthermore, the interference filter represents a unique simple method for probing higher spatial harmonics in the photorefractive grating.
Conduction band and trap limited mobilities in Bi12SiO20
Authors: Nouchi P. , Partanen J. P. , Hellwarth R. W.
Published: February 2023

The mobility of photoexcited charge carriers in photorefractive insulators can be measured with a holographic time-of-flight technique.1 By illuminating the crystal with two interfering 30 ps laser pulses at the wavelength of 532 nm, we create an instantanuous sinusoidal pattern of photoexcited charge carriers. A strong electric field E0 is applied across the crystal causing the sinusoidal pattern of charge carriers to drift with a velocity μE0, where μ is the mobility. With a proper choice of the interference fringe spacing Λ, the superposition of this drifting charge pattern on the complementary pattern of photo-ionized traps creates an observable oscillating space charge field. We probe this oscillation by diffracting a weak cw He-Ne beam from the refractive index grating that is created via the electro-optic effect. The period Pt of the observed oscillation is the time required for photoexcited charge carriers to drift over one spatial period Λ.
Elasto-optic and roto-optic contribution to the photorefractive effect
Authors: Zgonik M. , Günter P.
Published: February 2023

In a photorefractive experiment the space-charge grating is built-up along a certain axis and it modulates the refractive indices via the linear electro-optic (EO) effect. In many of the works in the field there is an on-going dilemma which EO coefficient and also dielectric constants to use in order to model the photorefractive effect.[1] The relevance of the question lies in the fact that the unclamped (stress-free) and the clamped (strain-free) values typically differ by more than a factor of two. Experiments in KNbO3[2] and BaTiO3[3] tend to indicate that the unclamped values are more appropriate. In this contribution we show that neither the clamped nor the unclamped linear EO coefficients are to be used without caution but the appropriate effective coefficients must be calculated for every particular crystal symmetry and sample orientation.
Photogyration and Photoinduced Structure Distortions in Doped LiNbO3 and LiTaO3
Authors: Kostritskii S.M.
Published: February 2023

In this work photoinduced phenomenons in iron-doped (C= 0,01; 0,038; 0,05; 0,07 wt.%) and copper-doped (C =0,01; 0,025; 0,04 wt.%) lithium niobate and lithium tantalate single crystals have been investigated using the Raman scattering (RS) and IR-reflection speotroscopy. The following types of lasers were used as illumination sourses: YAG:Nd3+ (λ = 10640 Å); He-Ne (6328 Å); Ar+(5145, 4880 Å); He-Cd (4416 Å).
Holographic recording and parametric scattering due to orthogonally polarized beams in BaTiO3
Authors: Holtmann L. , Krätzig E. , Goulkov M. , Odoulov S. G. , Sturman B.
Published: February 2023

Among the variety of photorefractive crystals BaTiO3 distinguishes by its large nondiagonal electrooptic coefficient r42 = 1600pm/V which enables efficient anisotropic diffraction [1, 2].
Parametric Scattering of Light in Photorefractive LiNbO3 Crystals
Authors: Zabrodin K.N. , Penin A.N. , Rubinina N.M.
Published: February 2023

A few years ago in photoretractive crystals of LiTaO3:Gu [1] and LlNbO3:Cu [2] a new nonlinear optic phenomenon, called the parametric scattering of “holographic type”, has been observed. As in the case of well-known [3] wide-angel spicies of photoinduced scattering, this process was degenerate. But it occured under condition of phase-matching for four coupling waves: and hence had narrow spatial spectrum, where KL, KS1, KS2 are the wave vectors of the pump and two phase-conjugated scattered waves on fequency ω.
Forward Phase-Conjugate Wave in Degenerate Four-Wave Mixing (DFWM) in Photorefractive Crystalline Slab
Authors: Zhang H. Y. , He X. H. , Tang S. H.
Published: February 2023

DFWM as an useful tool to generate phase conjugate waves has recently been the subject of intensive study. In particular photorefractive crystals such as LiNbO3, KNbO3, BaTiO3 and SBN are widely used[1]. Among the published papers on DFWM most are concerned with backward phase conjugate waves and only a few with forward phase conjugate, waves.[2,3] In both of these papers the intensity of the forward phase conjugate wave has not been investigated. We report here a systematic study of the intensity of forward phase conjugate wave.
Non-steady-state photoEMF in crystals with long relaxation times of photoconductivity
Authors: Sokolov I.A. , Stepanov S.I.
Published: February 2023

The recently discovered effect of non-steady-state photo(EMF) is a powerful technique for the measurement of different parameters of photorefractive crystals [1-3]. The photoEMF is observed as an alternating electric current Jω through a short-circuited sample of photoconductor illuminated by a vibrating pattern of interference between two coherent waves, one of which is phase modulated with frequency ω (Fig. 1). It results from a periodic modulation of the spatial shift between the distribution of photoconductivity that followes movements of the interference pattern and the distribution of the space-charge electric field recordered through the conventional diffusion holographic mechanism in photorefractive crystals.
Transport-induced-grating interferometry: application to photorefractive Bi12TiO20
Authors: Xia Ping , Partanen J. P. , Hellwarth R. W.
Published: February 2023

We have developed a technique to measure interferometrically charge-transport-induced refractive index gratings in photoconductive insulators. All four parameters needed to describe fully the interaction between the two beams Bragg matched to the grating can be determined. We use the method to find that the complex optical polarizability of an occupied charge trap equals that of an unoccupied trap plus (0.7 − i4.5 ± 0.7 ± i0.4) × 10−22 cm3 in photorefractive Bi12TiO20.
Reflection Grating Mutual Conjugator in the Geometry of Two Interconnected Ring Mirrors
Authors: Mamaev A. V. , Zozulya A. A.
Published: February 2023

Geometry for conjugation of mutually incoherent laser beams, consisting of two interconnected passive ring mirrors, was proposed in Ref.[1]. This is the only geometry among all known mutual conjugators, that can work equally well with either transmission, or reflection gratings recording. A detailed theory of this geometry and its experimental realization in the photorefractive SBN crystal in the case, when transmission gratings were operating, can be found in Ref.[1]. Here we report on the experimental investigation of a reflection grating mutual conjugator in the geometry of two interconnected ring mirrors in cw regime with the characteristic relaxation times of the order of several milliseconds.
Double Phase Conjugated Mirror and Double Colour Pumped Oscillator using Band-Edge Photorefractivity in InP:Fe
Authors: Wolffer N. , Gravey P. , Picoli G. , Vieux V.
Published: February 2023

The Double Phase Conjugated Mirror (DPCM)1 and the Double Colour Pumped Oscillator (DCPO)2 are particularly interesting devices for reconfigurable optical interconnects2,3,4,5. In a DPCM two mutually incoherent pump beams (at nearly identical wavelengths) incident on the opposite faces of a photorefractive (PR) crystal share a common grating which diffracts them into the phase conjugated of the opposite one. When the wavelength difference of the interacting beams is important (larger than the grating selectivity), they can still induce a common grating (DCPO). Recently DPCM has been observed in InP:Fe6 and GaAs:EL27 at 1.06 μm and DCPO has been achieved in InP:Fe using 1.06 and 1.32 μm wavelengths8.
Two-center model explains photorefractive properties of KNbO3:Fe
Authors: Holtmann L. , Kuper G. , Buse K. , Loheide S. , Hesse H. , Krätzig E.
Published: February 2023

KNbO3 has favourable photorefractive properties for applications in fast nonlinear optics such as image processing, coherent light amplification, [1] or self-pumped phase conjugation [2]. Desirable is the optimization of the sensitivity connected with the response time and the refractive index change. Only little is known about the centers involved in the photorefractive effect of KNbO3. Previous models were based on the assumption of iron impurities occuring in two valence states, Fe2+ and Fe3+, as sources and traps for the redistribution of charges [1]. But these models cannot explain a nonlinear response of photoconductivity on light intensity already observed earlier [3, 4].
Electron-Hole—Transport in Photorefractive Media
Authors: Bashaw M.C. , Ma T.-P. , Barker R.C.
Published: February 2023

Recently, electron-hole transport in photorefractive media has received much interest. Many observations which cannot be accounted for by simple single-carrier single-level transport can be explained by electron-hole transport. This summary describes electron-hole transport by two different models and describes a regime in which both models give similar results.
Spatial Subharmonic Generation at Intermode Interaction in Planar Waveguides
Authors: Popov V. , Shandarov E. , Shandarov S.
Published: February 2023

In papers 1-4 the possibility of new light beam generation by interactions of light waves in photorefrective crystals is shown. New beams appear due to the subharmonic formation of the main holographic grating. The analysis of subharmonic generation was carried out for crystals with nonlocal response2,3 and circular photogalvanic mechanism of grating recording4. The vector diagram illustrating the latter type of interaction is represented in Fig.1. Here, the generated beam 1(3) has polarization orthogonal to polarization of exciting waves 2,4.
Light-Induced Scattering in Planar Photorefractive Waveguides
Authors: Bashkirov A. , Glazov G. , Itkin I. , Pankovetz N. , Shandarov S.
Published: February 2023

The light-induced scattering is observed in photorefractive crystals due to noise hologram recording characterized by a complex angular spectrum1. The formation of such holograms in planar waveguides has a number of peculiarities because the recording speed of a waveguide holographic grating depends on its period2.
Carrier and Electric Field Picosecond Dynamics in Photorefractive GaAs:EL2 and CdTe:V Crystals: Modelisation and DFWM Experiments
Authors: Bastien L. , Jarašiūnas K. , Zališčevskis A. , Delaye Ph. , Roosen G.
Published: February 2023

Semünsulating III-V and II-VI semiconductors reveal optical nonlinearities of different origin under excitation by short laser pulses /1,2/.
Photorefractive response of n-type and p-type photoconductive Bi12GeO20 at low temperatures
Authors: Foldvari Istvan , Reeves Roger J. , Martin Joel J. , Powell Richard C.
Published: February 2023

The outstanding photorefractive properties of the sillenites (Bi12MeO20, Me = Si,Ge,Ti) have led to extended experimental and theoretical investigations which are well summarized in topical books and review articles [1-3].
Photorefractive effect in electron-irradiated GaAs
Authors: Delaye P. , Von Bardeleben H. J. , Roosen G.
Published: February 2023

Undoped GaAs is a well-known material that presents photorefractive (PR) properties in the infrared [1,2].
Connection of the Photorefraction with Induced Pressures in Lithium Niobate
Authors: Kanaev I. F. , Kostritskii S. M. , Malinovsky V. K. , Pubachev A. M.
Published: February 2023

It was demonstrated in / 1 / that in nominally pure LiNBO3 crystals the photogalvanic current depends substantially on the pressure.
Effect of the electron localization on light-induced scattering in photoretractive crystals
Authors: Junmin Liu , Simin Liu , Jinjun Xu , Guangyin Zhang
Published: February 2023

We first demonstrate the localization of the optically excited electrons and its influence on the light- induced scattering in photorefractive crystals.
Mirrorless Parametric Oscillation in BaTiO3
Authors: Odoulov S. , Sturman B. , van Olfen U. , Krätzig E.
Published: February 2023

Under certain conditions mirrorless parametric oscillation may occur in photorefractive crystals.
Beam Fanning in the Photorefragtive Crystal Ba2NaNb5O15.
Authors: Ivanova S. V. , Naumova I. I.
Published: February 2023

Photorefractive materials with the beam fanning are the subject of extensive research in the recent years [1-4].
Photoinduced Scattering with the Turn of Polarization in LiNbO3
Authors: Kanaev I.F. , Malinovsky V.K. , Surovtsev N.V.
Published: February 2023

Polarizationally-anisotropic light-induced scattering (PAS - scattering with the polarization change) in LiNbO3:Cu (0.1 weight %) and LiNbO3:Fe (0.1 weight %) has been investigated. The data indicate that there is considerable distinction between the time development of the PAS and one of the PIS (polarizationally-isotropic scattering). The more extended time delay of the evolution beginning and the more extended time of the attainment of a steady state (in 5*10 time) are typical for the PAS.
The Theory of Photorefractive Light Scattering
Authors: Obuhovsky V.V. , Stoyanov A.V.
Published: February 2023

Photorefractive crystals are perspective media for the prossesing and storage of holographic information. The most important limitations in their practical application are connected with the arising of strong light scattering (later on it will be named as photorefractive light scattering, PRLS) in the processes of optical recording [1]. In doped crystals LiNbO3, SBN, BaTiO3, etc. the PRLS is manifested so strongly that, in some cases, in can completely suppress the useful effects (image processing ang recording). On the other hand, PRLS is important for "holographic laser" operating [2].
Phase-matched light induced scattering in lithium niobate
Authors: Goulkov M. Yu.
Published: February 2023

The recording of dynamic hologram in medium with well pronounced nonlinearity is quite often accompanied by the appearance of rings and arcs of light-induced scattering [1].
Interband Photorefractive Effects in KNbO3 crystals
Authors: Montemezzani G. , Rogin P. , Zgonik M. , Günter P.
Published: February 2023

1. Introduction Photorefractive gratings are most often produced by illumination of an electro-optic crystal with laser light below the band gap and the absorbed photons induce photoexcitation and redistribution of carriers within mid-gap trap centers [11. The photorefractive response time is longer or equal to the time needed to photoexcite a large enough number of earners to create the space-charge field [2], To increase the speed of response, beside using higher light intensities, also a large absorption constant a of the crystal may be helpful. By doping, a can be increased only in a limited range. In contrast, large absorption constants are observed without doping at the band edge of any photorefractive material. In this region, the absorbed photons can induce interband phototransitions of electrons. The creation of photorefractive gratings by photoexcitation over the band gap has been demonstrated recently in multiple quantum well (MQW) devices [3-6]. However, the thickness of such multilayer structures is limited because of the epitaxial growth process and reasonable diffraction efficiencies are obtained only making use of resonant nonlinear effects at the band-edge. This limits the read-out wavelength range to a width of 10-20 nm and the optical interaction length to few µm. The use of oxide crystals with large linear electro-optic coefficients instead of MQW’s overcomes this problem because the read-out can be done at any wavelength in the visible or infrared. Even though the thickness of the photorefractive grating depends on the absorption constant and on the light intensity of the writing beams, the interaction length L can be increased to the crystal size by propagating the non-absorbed readout beams parallel to the crystal surface.
Ultraviolet photorefraction in LiNbO3
Authors: Jungen R. , Engel T. , Laeri F. , Tschudi T.
Published: February 2023

INDRODUCTION Up to now the main interest in photorefraction is focused in the visible and recently in the infrared part of the spectrum. For certain application however, photorefraction in the UV seems of great promise. Only Fridkin et.al. [1] and Montemezzani et.al. [2] reported results in the Ultraviolet with KDP at deep temperatures and Bi4Ge3Oi2 at room temperature, respectively. Some years ago, Orlcwski et.al. [3 examined LiNbO3 and LiTO3 doped with transition metals in the UV. The hole conductivity was increased due to oxidization of the samples. Since hole conductivity does not contribute to the photovoltaic effect, diffusion became the dominant charge transport mechanism in strongly oxidized crystals. Very high absorption inhibited further sensible examinations. In a recent publication [5] we reported a small photovoltaic field of approx. 550 V/cm for nominally undoped LiNbO3- crystals with moderate absorption at 35lnm. The charge transport is dominated by diffusion of photoexcited holes. We extended our investigation to the spectral dependence of photoconductivity- and wave mixing- experiments. The unique results additionally make feasible self pumped phase conjugation with an external ring and self enhancement effects if beams are diffracted at fixed gratings. In all experiments extraordinary polarisation and grating vector parallel to the crystals c-axis were chosen . to address the largest electrooptical coefficient r33 in LiNbO3.
Radio frequency summation in the phase-locked detection of a running interference pattern
Authors: Bobyr V. S. , Ilinykh P. N. , Zel’dovich B. Ya.
Published: February 2023

Phase-locked detection of a running interference pattern has been suggested and realized experimentally in Bi12TiO20, (BTO) [1] and now is studied in details for many materials [2,3]. Phase-locked detection of a running interference pattern has been suggested and realized experimentally in Bi12TiO20, (BTO) [1] and now is studied in details for many materials [2,3].
Recording of A Photorefractive Grating by Interference of λ and λ/2 Pulses.
Authors: Krivoschekov V. A. , Rogacheva L. F. , Zel’dovich B. Ya.
Published: February 2023

Mode locked Nd:YAG 70 picoseconds, λ=1.06 µm radiation and its second harmonic intersected in LiNbO3 crystal and recorded a hologram. Gratings of χ(2) in liquid crystals under same illumination are to be studied.
Defection of high-frequency phase-modulated signals by adaptive photodetectors
Authors: Sokolov I. A. , Kulikov V. V. , Ioffe A. F. , Stepanov S. I.
Published: February 2023

Registration of small acoustic vibrations of real diffusely scattering objects is a very important problem for different practical applications. The usage of high-sensitive, contactless homodyne laser vibrometers seems to be very attractive for such measurements [1].
On the Correlation between Acoustic and Dislocation Subsistems in the Crystals DKDP at the High-Temperature Photorefraction
Authors: Anikeev B. V. , Gurkin O. A. , Sin’ko D. V.
Published: February 2023

The new type photorefractive effect in crystal of DKDP (PR) (which we for the first time discovered [1]) appear according to the experiments in present of the strong polarisation of medium (induced by the laser’s pulse ⩾ 4J/sm2) consisting of fast- (10−6 s) and slow-relaxing (10−1s) components. The fast component arises only on base slow component.
Nondiagonal Component of Photovoltaic Tensor in LiNbO3:Cu and LiTaO3:Cu Crystals
Authors: Karabekian Suren , Obukhovsky Vyacheslav
Published: February 2023

The results of linear photovoltaic currents measurements in doped lithium niobate and tantalate crystals are presented.
Conjugate Cavities with Large Gain for Magnifigation of Phase/Amplitud Object Images
Authors: Vasillev Yu. , Kazaryan M. , Kuznetsova T.
Published: February 2023

The exponential gain factors for various types of coherent light amplifiers reach the values of 0, 1-1 cm-1 (for metal vapors [1]) and even up to 100 cm-1 (for photorefractive crystals [2]).
Some Peculiarities Op Magnus Optical Effect in a Fiber/Crystal System by Polarization Information Translation
Authors: Fadeeva T.V. , Volyar A.V.
Published: February 2023

Magnus optical effect in gradient and step index multimode fibers tends to twist and oscillate a ray trajectory of a local wave depending on a present magnitude of a polarizing state [1,2] Experimentally this effect is developed as a speckle position change in a radiation field of a multimode fiber in changing the polarizing state of an exciting field.
Performance of Optical Limiters Using Photorefractive BaTiO3 M.B. Klein
Authors: Dunning G. J. , Brown W. P. , Wechsler B. A.
Published: February 2023

Photorefractive materials can be used for devices which have the useful property of being able to attenuate a strong coherent beam in the presence of a weak white-light image.
Photorefractive Phase-Shift Measurement with Self Diffraction Effects
Authors: Frejlich Jaime
Published: February 2023

Hologram phase-shift data provide with useful information on the recording mechanism and the intrinsic parameters of photorefractive crystals [1,2].
Word Recognition Using Photorefractive Time-Delay Networks
Authors: Zhou Gan , Anderson Dana Z.
Published: February 2023

The time-delay network was first proposed by Hopfield and Tank [1,2] as a dynamic architecture that continuously recognizes temporal sequences.
High capacity, compact holographic storage in a photorefractive crystal
Authors: Tao S. , Selviah D. R. , Midwinter J. E.
Published: February 2023

Dense holographic storage in photorefractive materials has received considerable interest due to the potential for a large storage capacity of high resolution images and rapid parallel access [1-3].
Heterodyne detection of weak optical wavefronts buried in a photorefractive fanning noise
Authors: Breugnot S. , Rajbenbach H. , Defour M. , Huignard J.P.
Published: February 2023

Wave mixing in photorefractive media offers attractive capabilities to perform wide field-of-view homodyne and heterodyne detection.
Bi2TeO5 - a new nonlinear optical material for photorefractive memory applications
Authors: Foldvari Istvan , Peter Agnes , Powell Richard C. , Reeves Roger J.
Published: February 2023

The first observation of a Bi2TeO5 crystal composition was published in 1971 [1].
Electro-optic and dielectric properties of photorefractive KNbO3
Authors: Zgonik Marko , Günter Peter
Published: February 2023

The determination of the complete set of material parameters of KNbO3 relevant for photorefractive experiments has been recently accomplished.
Optical Damage Resistant Impurities in Lithium Niobate.
Authors: Volk T.R. , Rubinina N.M.
Published: February 2023

Investigations of damage resistant impurities in LiNbO3 crys­tals are of great interest both for practical applications and for understanding microscopic origin of photovoltaic anu phog torefractive centers.
Photoelectrical properties of BaTiO3 crystals grown by Czochralsky and Remeika methods
Authors: Bochkova T.V. , Bunina L.K. , Kruzina T.V. , Kudziu A.Yu. , Pozdeev V.G. , Sokoljansky G.Ch.
Published: February 2023

The barium titanate has been attracting much attention over the past 50 years. The physical properties of BaTiO
3
has been widely investigated in both the single crystal and ceramic forms.
Photorefractive Response of Co-Doped SBN Crystals on Quasi-CW Radiation
Authors: Dadasyan A. Ya. , Ivleva L. I. , Mamaev A. V. , Orazov K. , Polozkov N. M. , Shkunov V. V.
Published: February 2023

It seems to be reasonable to expect that the fine temporal structure of the mixing waves in photorefractive crystals can strongly impact on the photorefractive process characteristics.
Some Optical Properties of new Monocrystals in Bi2O3-V2O5 and Bi2O3-P2O5 Oxide Systems
Authors: Duda V.M. , Dudnik E.F. , Prushko I.V.
Published: February 2023

In many cases independently on structure compounds of bithmuth-contained complex oxides are very attractive materials for the use as medium for the optical information processing.
Picosecond Laser-induced Grating Signals in Cr4+-doped Crystals
Authors: Liu Huimin , Jia Weiyi , Leyderman Alexander
Published: February 2023

Cr4+-doped crystals are of current interest in the research of the tunable solid state laser materials.
Crystal Growth and Optical Perfection of Ce:SBN Crystals Grown From the Congruent Melt Composition
Authors: Uhrin R. , Latore J. R. , Samuelson S.
Published: February 2023

Material and hardware advances are making volume holographic storage more practical (1).
Energetic Spectrum Defects of Undoped and Al, Ga-Doped Bi12SiO20 Crystals
Authors: Panchenko T.V. , Snezhnoy G.V.
Published: February 2023

Photorefractive materials Bi12SiO20 (BSO) are very interesting objects for the use in optical recording and information processing devices due to their suitable physical properties, which depend on the content of impurities and defects in crystals.
Experimental effects of light intensity modulation on the recording and erasure of holographic gratings in BSO crystals
Authors: Alvarez-Bravo J.V. , Carrascosa M. , Arizmendi L.
Published: February 2023

The knowledge of nonlinear effects due to light modulation values near unity is important from a practical point of view.
Noncoherent Phase Conjugation in Bi12 TiO20
Authors: Petrov M.P. , Mokrushina E.V. , Toropov A.V. , Mendes E. , Tentori D.
Published: February 2023

A noncoherent scheme of wavefront conjugation is interesting not only from the scientific, but also from the practical point of view, because it ensures highly stab le and interference-free measurements.
Photoconductivity of BGO and BSO Crystals
Authors: Bunina L.K. , Kudzin A. Yu. , Sokoljansky G.Ch.
Published: February 2023

The energy gap of Bi12GeO20 BGO and Bi12GeO20 BSO crystals is about 3.2eV.
Photorefractive response of BTO in near infrared region of spectrum
Authors: Odoulov S. G. , Shcherbin K. V. , Shumelyuk A. N.
Published: February 2023

In spite of the large bandgap (of order of 3.3 eV) of the sillenite ecrystals they may exhibit the sensitivity to recording in Near InfraRed (NIR) region of spectrum [1,2].
Threshold Conditions of Oscillation for DPCM with Local Response Medium
Authors: Ilyenkov A. , Odoulov S. , Soskin M. , Vasnetsov M.
Published: February 2023

Oscillation in double phase conjugate mirror [1] with the local response medium (unshifted gratings) is possible under following conditions [2]: 1) frequency detuning of oscillation waves with respect to the incident pump waves and 2) angular deviation of oscillation waves from strictly counterpropagation direction with respect to the pump waves.
Autowaves in Scattering as the Evidence of a Self-Organization of Optical Fiflds in Photorefractive Crystals
Authors: Lemeshko V. V. , Obuhovsky V. V. , Stoyanov A. V.
Published: February 2023

Previously it was found [1] that during steady-state optical illumination of the photorefractive crystal LiNbO3:Fe along the optical axis by a focused laser beam (λ = 0.44 μn) the new effect (named "autowave scattering" (AWS) ) took place: we observed a periodic appearance of a scattering in the form of cones directed opposite the pump.
Forward mixing of two mutually incoherent beams in a photorefractive crystal
Authors: Dolfi D. , Delboulbé A. , Huignard J. P.
Published: February 2023

Two-wave mixing (2WM) of mutually incoherent beams in a counterpropagative geometry has been demonstrated and analyzed in various photorefractive materials [1-5].
Self-Bending of a Double–Gaussian Beam in Photorefractive Media
Authors: Lyubomudrov O.V. , Shkunov V.V.
Published: February 2023

For different phase-conjugate schemes in photorefractive crystals with string diffusion-grating response a phenomenon of self-bending of an introduced beam trajectory is observed [1-4].
Ferroelectric hysteresis loops, space-charge fields and hologram fixing in top-seeded solution grown barium titanate
Authors: Cudney R. S. , Fousek J. , Zgonik M. , Günter P. , Garrett M. H. , Rytz D.
Published: February 2023

Long before becoming famous for its large Pockels coefficients and strong photorefractive behaviour, barium titanate was well-known for being a ferroelectric.
Photorefractive GaInAP:Fe/InP:Fe Semiconductor Waveguide
Authors: Chauvet M. , Hervé D. , Mainguet B. , Salaün S. , Le Corre A. , Viailes J. E.
Published: February 2023

The photorefractive effect can be used in image amplification, optical phase conjugation and even optical switching [1].
Surface Waves in Photorefractive Materials
Authors: Daisy Ron , Fischer Baruch
Published: February 2023

The large optical nonlimarities of photorefractive materials have motivated much research and a variety of applications in the last years.
Photoinduced Structural Transformation in Silica Glass: Mechanism for UV-Written Refractive Index Gratings?
Authors: Sulimov V.B. , Sokolov V.O. , Dianov E.M. , Poumellec B.
Published: February 2023

Photoinduced transition in silica glass from quartz- to rutile-like structure initiated by a strong relaxation of excited oxygen vacancies is proposed as a cause of refractive index change.
Long-period cladding-mode-coupled fiber gratings: properties and applications
Authors: Vengsarkar A. M. , Lemaire P. J. , Jacobovitz-Veselka G. , Judkins J. B. , Bhatia V. , Erdogan T. , Sipe J. E.
Published: February 2023

In a recent paper,1 we introduced compact, low insertion-loss long-period optical fiber gratings that function as spectrally-selective loss elements. These devices are useful as ASE filters to improve erbium amplifier performance and as band-rejection filters in Raman lasers/amplifiers.2 In this paper, we present a detailed description of their properties in terms of their dependence on strain, temperature, recoating and sensitivity to bends. Two new applications, gain-flattening of optical amplifiers and stabilization of errant laser diodes, are described.
Efficient Photo-induced Second Harmonic Generation in Ternary Barium Borosilicate and Pure Binary Lead-silicate Glasses
Authors: Nageno Y. , Kyung Jae H. , Lawandy N.M.
Published: February 2023

Most studies of photo-induced efficient second harmonic generation (SHG) in bulk glass systems are currently being performed with commercial glasses which are highly impure. The existence of impurities, even trace amounts, can significantly affect the photo-induced SHG characteristics in glasses as demonstrated in experiments performed on Ce-doped lead germanate glasses [1]. In fact, it was shown that Ce concentration as low as 0.2% was enough to cause a significant increase in SHG in these glasses. Therefore, it is advantageous to study glass systems that are devoid of impurities and consistent in composition in order to gain a better insight into the role of the glass matrix in photo-induced SHG. In a series of experiments performed by Dianov, et al [2], the effect of PbO concentration on SHG was studied using commercial lead-silicate glasses with different lead-oxide concentrations. They found a peaked correlation between lead concentration and SHG power at approximately 21 mol % PbO. However, the effects due to the presence of impurities and variations in composition in different lead-silicate glasses were not addressed. In this study, we measured compositional dependence on SHG characteristics on pure binary lead-silicate and pure ternary barium borosilicate glass systems.
Evidence of Densification in UV-Written Bragg Gratings in Fibres
Authors: Riant I. , Borne S. , Sansonetti P. , Poumellec B.
Published: February 2023

Photorefractivity observed in an optical fibre germanium doped core at 240nm, allows the realization of fibre grating devices of great interest for optical telecommunications [1]. To master Bragg grating fabrication or predict the life time of those components, it is necessary to understand the involved physical phenomenons. Several mechanisms are proposed, essentially based on Kramers-Kronig conjugation [2,3]. However, by performing interferometric microscopy measurements at the surface of germanosilicate preforms after Bragg grating inscription, we have pointed out a corrugation. They are accounted for by a model of photoinduced densification grating [4,5]. If explains the major part of photorefractive index change In BPG285 preforms [6]. We generalize here the conclusions by presenting measurements done on a preform made in our laboratories and, for the first time, on the associated optical fibre.
Moving fibre/phase mask-scanning beam technique for writing arbitrary profile fibre gratings with a uniform phase mask
Authors: Cole M. J. , Loh W. H. , Laming R. I. , Zervas M. N.
Published: February 2023

Fibre Bragg gratings are by now well-recognised as key components for many fibre optic and laser systems, but ways for improving their characteristics and ease of fabrication continue to be a subject of considerable research interest. In particular, much of the recent activity has centred on the use of phase masks for grating production[1,2].
Comparison of UV Photosensitivity and Fluorescence During Fiber Grating Formation
Authors: Patrick Heather , Gilbert Sarah
Published: February 2023

We have conducted a comparison of the UV photosensitivity of optical fiber with the blue fluorescence emitted during the exposure. In a survey of ten non-hydrogen-loaded germanium-doped fibers, we measured the UV photosensitivity and monitored the blue fluorescence during the growth of fiber gratings. Our goal was to determine whether the initial fluorescence, or the change in the fluorescence during exposure, is correlated with the index change. This provides insight into the underlying physical mechanism of UV-induced index change and also determines whether the blue fluorescence can be used as an indicator of the photosensitivity of a fiber.
Photochemical Start-Up of Photorefractivity in SiO2 and SiO2: GeO2 Glasses
Authors: Marchenko V.M.
Published: February 2023

Progress in applications of photosensitivity of silica glasses for fabrication of reflection optical fiber gratings is restrained by an obscurity of nature of photorefractivity of the glasses. There is a lot of inconsistent interpretations of spectral properties of oxygen deficient centers (ODC) responsible of UV absorbance of the glasses. Photoinduced refractive index variations of the glasses are in accordance with Kramers- Kronig relation due to the absorbance changes. As much as ~ 10-4 photoinduced index variation of Ge- doped silica at 1.5 μm is for instance explained by photobleaching of 5.1 eV spectral band and increasing of absorptivity of 6.5 eV band [1]. However experimentally obtained index changes larger than 10-3 are probably caused by changes of the absorbance at shorter wavelengths corresponding to energy gap transitions and consequently accompanied by modification and compaction of glass matrix [2]. In this work, the interpretation of ODC optical spectra of SiO2 and SiO2:GeO2 glasses is discussed and model of the solid-state photoinduced chemical reactions is proposed to explain the start-up of physical and chemical processes of varying of ODC concentrations and macroscopic parameters of the glasses which is confirmed by the analysis of ODC preparation technique.
Photosensitivity of Ge-doped silica films deposited in a PECVD hollow cathode reactor
Authors: Bazylenko M. V. , Gross M. , Chu P.L. , Moss D.
Published: February 2023

In recent years there has been a considerable research effort directed towards the process and applications of the UV induced refractive index change in germanosilicate glasses. Most of the germanium doped planar structures reported in previous work were formed by flame hydrolysis and need to be hydrogen loaded for up to 2 weeks [1] to become reasonably photosensitive. An alternative deposition technique, which is able to produce photosensitive films without hydrogen loading is Plasma Enhanced Chemical Vapour Deposition (PECVD). A UV induced refractive index change of 0.0025 has been reported for germanium doped PECVD silica films without use of hydrogen loading [2].
Linear and nonlinear effects in deep gratings superstructures
Authors: Broderick N. G. R. , de Sterke C. Martijn , Eggleton Benjamin J.
Published: February 2023

Recent developments in fibre grating writing techniques have lead to the fabrication of gratings whose parameters vary periodically along the optical fibre.1,2 Such grating superstructures may have significant applications in fibre lasers, as they can be designed to have a reflection spectrum spanning the entire Erbium gain bandwidth2. Grating superstructures have earlier been investigated in semiconductor geometries,3-5 and have also been studied theoretically.6,7 Much of the previous analysis is applicable to weak gratings superstructures; in contrast we present here a general approach which is suitable for deep grating superstructures as well. Such a general description is pertinent for grating superstructures in optical fibre,1 where, although the refractive index modulation is small, the variations in the modulation can be large.
Theory of Transient Self-pumped Phase Conjugation in Photorefractive Materials
Authors: Lam Juan F.
Published: February 2023

The discoveries of self-pumped phase conjugation in barium titanate by White et al1 and by Feinberg2 have provided the impetus for the practical implementation of loaded phase conjugate resonators3, demonstration of optical convolution and correlation4, and application of the thresholding property to associative memories5.
Modeling of Self-Pumped Single Barium Titanate Crystal
Authors: Goff John R. , Brody P.S.
Published: February 2023

We have earlier described a detailed mechanism of self-pumped phase conjugation in a barium titanate crystal [1]. The proposed mechanism was motivated and supported by observations of light paths in the crystal, and differs in some respects from better-known previous explanations of similar phenomena [2]. Our model attaches particular significance to a proposed resonance between two opposite reflecting corners and to the simultaneous existence of a system of cooperating transmission and reflection gratings. We show the operation of the hypothesized system of gratings, as simulated by computer analysis. The results show many points of agreement with the actual behavior of the self-pumping crystal.
Ultrafast Photorefractive Process in BSO
Authors: Ferrier J.L. , Gazengel J. , Rivoire G.
Published: February 2023

The permanent photorefractive effect induced in Bi12 SiO20 crystals by intense nano and picosecond pulses shows a long rise-time (in the range 10 - 100 ms), and a diffraction efficiency limited to values ~ 5.10-4.(1)(2) These limitations are connected with the existence of transient effects characteristic of intense and fast excitations.