Nonlinear Dependence of Response Rateon Intensity in Doped KNSBN Crystals

l.IntroductionThephotorefractiveresponserateisacritica1issuebecauseitdirectlydeterminestheprocessingsPeedofphotorefractivedevices[1]-TherelationshipbetweentheresPonserateandthelightintensitycanprovideusefuIinformationaboutthedefectlevels,theprocessofchargeCarriersexcited,transportedaMdtrapPed["'].Conventionalsing]elevelmod-e1s[4jpredictthatthephotorefractiveresponserateislinearlydePendentonthelightinten-sity.However,experimentaldatashowedthatthephotorefractiveresponserateofsomecrystalsvarie…     

Explanation of Anomalous Diffractive Behavior with New Model in Doped KNSBN Crystals

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Kinetics of Pulse Cathodoluminescence in Lithium–Gadolinium Orthoborate Crystals Doped with Cerium Impurity

Physics of the Solid State - The relaxation kinetics of electron excitations in single-crystal and crystal-fiber Li6GdB3O9 samples was studied by the time-resolved methods of pulse absorption...     

Holographic and Thermal-Fixing Characteristics of Doubly Doped Zn：Fe：LiNbO3 Crystals

We perform a comprehensive experimental study on holographic and thermal-fixing characteristics of Zn：Fe：LiNbO3 The measured hologram decay time constants, respectively caused by optical readout and under dark condition, with thermal fixing are 15 times and 75 times longer than that obtained without thermal fixing. This suggests that Zn：Fe：LiNbO3 crystals are suitable for thermal fixing. Multiplexed recordings of 300 holograms using different thermal fixing schemes verify that a proper multiplexing scheme such as track-division thermal-fixing scheme for disc-type holographic storage can effectively compensate for the negative effect of zinc-doping on the dynamic range, thus the storage density is enhanced.     

Luminescent Method of Measuring the EXAFS Spectra of Structural Defects of Alkali‐Halide Crystals

It is shown that xray spectral methods — those of EXAFS and XEOL spectroscopy — allow determination both of the structure of inherent or impurity centers of luminescence in alkalihalide crystals and investigation of the dynamics of their change under the action of ionizing radiation. The methods are noted for high sensitivity. The possibilities of the methods are demonstrated for KBr, NaCl:Ni, and NaCl:Ni,Cu crystals taken as an example. New data on the structures of different luminescence centers investigated and dynamics of their change are obtained.     

Formation and Photoluminescence Properties of Porous Silicon Produced in Iodine‐Containing Electrolytes

Samples of porous silicon have been produced and investigated for the first time by the method of anodizing in a modified iodinecontaining electrolyte. It is shown that the addition of iodine to the electrolyte, all other things being constant, substantially influences the formation of porous silicon and leads to the occurrence of photoluminescence in poroussilicon layers on highly doped substrates of silicon of the n ⁺type. The morphology of the surface of the produced poroussilicon samples has been investigated and a marked decrease in the inhomogeneity scale as compared to the nonluminescent porous silicon produced without iodine under the same conditions has been detected. Investigation of the dependence of the spectral properties of photoluminescence on the density of the anodizing current has shown that with increase in the current density the maximum of the photoluminescence spectrum shifts to the shortwave region and the halfwidth of the photoluminescence spectrum decreases.     

Mechanical and Magnetostrictive Properties of Fe—Doped Ni52Mn24Ga24 Single Crystals

To improve the magnetic and mechanical properties of a Heusler alloy of Ni52Mn24Ga24,iron was doped with some cotents,Single crystals of the pseudoquaternary Heusler alloy of Ni52Mn8Fe15Ga24 have been synthesized for mechanical and magnetostrictive measurements.The magnetostriction loops and stress-strain curves were measured under different coupled magnetic-mechanical loads.The experimental results show that the brittleness of the sample is clearly improved and Yong‘s modulus of 13.7GPa is obtained in the [001] direction due to the part substitution of Fe for Mn.Furthermore,the toughness and Vickers hardness of the sample are also given by use of the indentation technique.     

Crystallization Behavior of Rare‐earth Doped Luminous Pigment/Polyamide 6 Composites

The crystallization behavior of well‐dispersed rare‐earth doped luminous pigment/polyamide 6 (PA6) composites prepared through in situ polymerization was investigated by DSC. The rare‐earth doped luminous pigments could accelerate the forming of γ form crystals and also had a great effect on the crystallinity and crystallization rate of PA6 composites. The Ozawa, Jeziorny, and Mo methods were used to analyze the non‐isothermal crystallization kinetics. It was found that the Ozawa method was unsuitable for non‐isothermal crystallization of PA6 composites. The results of Jeziorny analysis showed that the crystallization rates of PA6 composites increased when the luminous pigment content was larger than 5 wt.%. Mo's analysis also showed that the presence of the pigment shortened the crystallization time and accelerated the crystallization rate. Polarized optical microscopy showed that the spherulites became smaller with increasing of the luminous pigment amount due to the heterogeneous nucleation.     

Analysis of hyperfine structure of Rare‐Earth Ions in Single Crystals by Electron Paramagnetic Resonance Spectroscopy

Electron paramagnetic spectroscopy of rare‐earth ions in single crystals is an interesting tool to analyze the hyperfine structure of the ground state of the rare‐earth. This can be useful for coherent spectroscopy and quantum information applications where the hyperfine structure of the electronic levels is used. Moreover, in some cases, the electron paramagnetic resonance hyperfine structure of interacting rare‐earth ions allows us to retrieve the isotropic exchange interaction between the two interacting ions. We illustrate these points with the hyperfine structure of Yb³⁺ ions in vanadate crystals, the hyperfine structure of Er³⁺ ions in Y₂SiO₅, and the hyperfine structure of Yb³⁺ pairs in CsCdBr₃.     

A Study of Electrical Characteristics of Crystals of Homogeneously Doped LiNbO3:Zn,Mg in the Temperature Range of 450–900 K

Technical Physics - In a series of initially polydomain crystals of LiNbO3:Zn,Mg obtained by the homogeneous doping of the crystals in the concentration ranges of around 1 ± 0.02 mol % MgO and...     

Holographic Recording Media Based on Poly‐N‐Epoxypropylcarbazole Films Doped with Organic Dyes

A comparative analysis of the recording media based on polyNepoxypropylcarbazole films doped with cationic, anionic, and intraionic organic dyes has been carried out for the purposes of holographic interferometry. It is shown that in the case of application of intraionic dyes recording media have satisfactory information characteristics. The use of anionic and cationic dyes does not give a positive result because of the absence of the photoconductivity effect in the anionic dyes and of the high electrical conductivity of the films on increase of the temperature of the cationic dyes. The effect of longterm storage of a latent image in the films with intraionic dyes makes it possible to use them for recording holograms with several exposures.     

A Condition in Ln‐Doped Materials for Flat Optical Gain

Fundamental conditions that rule gain flatness in Er‐doped glass optical amplifiers are investigated using few parameters obtained by drastic simplifications for level positions and widths. The obtained general gain flatness condition for rare‐earth–doped glasses contains two parts: a general one valid in any material and a slight modulation of it valid only for glasses when “0–0” transitions are involved. Essentially, the electron–phonon coupling for the considered materials has to be larger than 2/3. In order to exemplify these conditions, they are calculated for fluoride and silicate glasses, which are known to display respectively flat and non‐flat gain behavior.     

Reflection Spectra of Single Crystals of La2CuO4−x ‐Type Metal‐Oxide Compounds

We have investigated the reflection spectra in polarized light at 80 and 295 K in an energy region of 1.0–4.8 eV for the single crystals of ternary and quaternary copperoxide systems with the participation of rareearth elements (La₂CuO_4–x , LaCuO₄, Pr₂CuO_4–x , GdBa₂Cu₃O_7–x , and LaSrCaCuO).     

Spectral Study of Fullerene Doped Optical Glasses

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Spectroscopic, Phototropic, and Lasing Properties of Cd1−x Mn x Te Single Crystals Doped With Chromium Ions

The spectroscopic properties of Cr²⁺ ions in Cr:Cd_1–x Mn _x Te (CMT) crystals are studied, and the possibility of using these impurity crystals as active media and saturable absorbers of solidstate lasers of medium IR range is demonstrated. The bands of absorption with a maximum at 1.9 m and of luminescence with a maximum at 2.6 m correspond to the transitions between the levels ⁵ T ₂ and ⁵ E of the tetracoordinated Cr²⁺ ions with more than 1·10^–18cm² cross sections. The pulsed and continuous lasing modes of a Cr:CMT laser are realized in the 2.6m region. The Cr:CMT crystals are characterized by effective saturation of impurity absorption. The cross sections of absorption from the ground and excited states of the Cr²⁺ ions at = 2.09 m are determined: _gsa = 1.1·10^–18 cm²; _esa/_gsa < 0.1. With the use of the Cr:CMT crystals as a passive gate the regime of Qswitching of the Cr,Tm,Ho:YAG laser emitting at = 2.09 m is obtained.     

Preparation and Characterization of Nano‐TiO2 Doped Polystyrene Materials by Melt Blending for Inertial Confinement Fusion

Abstract

Nano‐TiO₂ doped polystyrene (PS) materials (TiO₂‐d‐PS) used for inertial confinement fusion (ICF) targets were prepared by means of melt blending. The effect of the pretreatment process, including coupling agents and ultrasonic dispersion on nano‐TiO₂, was studied. Tensile tests were conducted to evaluate the mechanical properties of the TiO₂‐d‐PS materials. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) was used to characterize the degree of dispersion of nano‐TiO₂ in the PS matrix. Transmission electron microscopy (TEM) and dynamic contact angle (DCA) measurements were introduced to demonstrate the surface state of untreated and pretreated nano‐TiO₂. The results showed that coupling agents improved the interfacial adhesion between the PS matrix and dopants; ultrasonic dispersion contributed to the increase in the tensile properties of the TiO₂‐d‐PS materials. The dispersion stability of nano‐TiO₂ powder and the stability of the TiO₂‐d‐PS materials were significantly enhanced through pretreatment, which was supported by the increase in the DCA when the nano‐TiO₂ was pretreated by the coupling agent. The results of SEM and EDS indicated that the nano‐TiO₂ dispersed homogeneously in the PS matrix. The pretreatment process is an effective way to break the aggregation of nano‐TiO₂, which was confirmed by TEM results. Melt blending is a feasible method to prepare PS doped high Z element ICF target materials.     

Kinetics of the Processes of the Change in the Concentration of Photosensitive Paramagnetic Centers on Excitation and De‐Excitation of ZnCdS Single Crystals

The EPR technique is used to study the behavior of photosensitive paramagnetic centers (PPC) in zinc sulfidebased single crystals under different conditions of excitation by UV radiation.     

Photoluminescence of Dislocations in Nitrogen Doped Czochralski Silicon

We investigate optical properties of dislocations in nitrogen-doped and nitrogen-free Czochralski silicon. The dislocations are formed during crystal growth, but not formed during deformation. The results show that in nitrogen-doped samples, a broad band replaced the D1 band of dislocation, regardless of dislocation density. The replacement of D1 band is caused by the non-irradiation combination induced by oxygen precipitation. Moreover,a new emission at 0.975 eV is observed in both the nitrogen-free and doped samples when the dislocation density is lower than 104 cm-2.     

Electron Paramagnetic Resonance and Optical Absorption of VO2＋ Doped Bis （glycinato） Mg （II） Monohydrate Single Crystals

We investigate the electron paramagnetic resonance （EPR） of VO2＋ ions in bis （glycinato） Mg （II） monohydrate single crystals at room temperature. Detailed EPR analysis indicates the presence of only one VO2＋ site. The vanadyl complexes are found to take up the substitutional position. The angular variation of the EPR spectra in three planes a＊b, bc and ca＊ are used to determine principal g and A tensors. The values of spin Hamiltonian parameters are gx= 2.1447× 10-4, gy= 1.9974×10-4, gz= 1.9131×10-4, Ax= 49×10-4, Ay= 60×10-4, Az= 82×10-4 cm-1. The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental data. By correlating EPR and optical data, different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.