(100-x)GeS2-x[0.5Ga2S3-0.5CdS]玻璃的电致二阶非线性光学效应的结构依赖性

采用熔融一急冷法制备了(100-x)GeS2-x[0.5Ga2 S3-0.5CdS]硫系玻璃,通过Maker条纹法研究了5kV、280℃、30min的极化条件下,SH强度、二阶非线性系数χ(2)大小的结构依赖性.结果表明,玻璃的SH强度和二阶非线性系数χ(2)与组成的变化关系曲线不呈线性变化,当x=30时,达最大值(χ(2)≈4.36pm/V),是因为随Ga2S3、CdS引入量的增加,玻璃的无规网络的连接程度先逐渐增强然后逐渐减弱,偶极子数量先逐渐减少然后逐渐增加,导致极化后玻璃中重新分布进行取向性调整的偶极子数量不同所致.     

Effective diffraction gratings via acidic etching of thermally poled glass

Relief diffraction gratings are formed via acidic chemical etching of a periodically poled soda-lime glass. The thermal poling under 1000 V DC is performed at 325 °C using a thermally stable glassy-carbon anodic electrode with periodic grooves, the depth of the grooves being of ∼650 nm. Poling-induced modification of the glass results in deepening the glass anodic surface in the regions under the ribs of the anodic electrode due to volume relaxation and in increasing chemical durability of these regions in acidic media comparatively to the virgin glass. Chemical etching of the poled glass in NH₄F:8H₂O solution allows additional to the thermal poling shaping of the glass surface via faster dissolution of unpoled/less poled glass regions. The morphology of the glass surface before and after the etching is characterized with atomic force and scanning electron microscopy. About 30 min etching provides the formation of ∼0.9 μm in height relief diffraction gratings with the diffraction efficiency close to the theoretically achievable ∼30% for multi-order diffraction. In vivo measuring of the diffraction efficiency in the course of the etching allows precise fabrication of the gratings.     

二阶非线性光学玻璃的研究进展

二阶非线性光学玻璃的研究在现代信息技术的发展中占有重要地位 ,己成为光电子技术领域中最尖端的课题之一。本文重点评述了近年来国内外在二阶非线性光学玻璃领域的研究进展 ,分别从各种玻璃系统中诱导二次谐波发生 (SHG)的激光诱导极化、电场 /温度场极化和电子束辐射极化等方法。讨论了SHG的理论模型和实验研究。最后展望了未来二阶非线性光学玻璃的研究方向和应用前景。     

Second harmonic generation from electrically polarized CuCl-microcrystallite-doped glass

Second harmonic generation has been observed in electrically polarized CuCl-microcrystallite-doped glass. The glass was prepared by means of melting–quenching method and poled at 200°C for 1 h under applied dc field of 4 kV. The incident angular variation of SHG intensity for the polarized glass was measured. To explain the effect, it is proposed that the second-order nonlinear polarization results from the dipolar orientation in the glass.     

Large enhancement of second harmonic generation in highly cerium doped lead-phosphate glass

The influence of lead and cerium concentration on photoinduced second harmonic generation (SHG) in lead-phosphate glasses has been studied. It has been shown that SHG can be considerably enhanced by increasing of lead and cerium concentration. We also have found that cerium greatly extends the induced nonlinearity lifetime. Physical mechanism of the phenomenon is discussed.     

热极化和电晕极化铁电PVDF薄膜的成分和结构

用高分辨率X-射线光电子能谱（XPS）研究了热极化和电晕极化的PVDF薄膜的成分和结构的变化。结果表明：PVDF薄膜的热极化和电晕极化反应过程和机理不同。在热极化过程中.高温强电场作用使PVDF薄膜产生了少量的F^-自由基,继而产生HF,形成了新C=C键：怛是,在电晕极化过程中荷能粒子使PVDF产生了H^＋自由基。热极...     

Theory of second harmonic thermal-wave generation: One-dimensional geometry

The analysis of the thermal-wave second harmonic generation induced by the time-modulated heating of the material with temperature-dependent heat capacity C(T) and thermal conductivity k(T) is presented. The developed theory describes nonmonotonic behavior of the second harmonic amplitude in a semiinfinite medium. An enhanced spatial resolution of nonlinear photothermal imaging in materials with dominant role of the k(T) temperature dependence (i.e., for is predicted.On leave from International Laser Center, Moscow State University, 119899 Moscow, Russia.On leave from Jenoptik GmbH, Jena, Germany.     

Nonlinear Optical Sulfides LiMGa8S14 (M = Rb/Ba,Cs/Ba) Created by Li+ Driven 2D Centrosymmetric to 3D Noncentrosymmetric Transformation

Cations that can regulate the configuration of anion group are greatly important but regularly unheeded. Herein, the structural transformation from 2D CS to 3D noncentrosymmetric (NCS, which is the prerequisite for second-order NLO effect) is rationally designed to newly afford two sulfides LiMGa₈S₁₄ (M = Rb/Ba, 1 ; Cs/Ba, 2 ) by introducing the smallest alkali metal Li⁺ cation into the interlamination of 2D centrosymmetric (CS) RbGaS₂. The unusual frameworks of 1 and 2 are constructed from C₂-type [Ga₄S₁₁] supertetrahedrons in a highly parallel arrangement. 1 and 2 display distinguished NLO performances, including strong phase-matchable second-harmonic generation (SHG) intensities (0.8 and 0.9 × AgGaS₂ at 1910 nm), wide optical band gaps (3.24 and 3.32 eV), and low coefficient of thermal expansion for favorable laser-induced damage thresholds (LIDTs, 4.7, and 7.6 × AgGaS₂ at 1064 nm), which fulfill the criteria of superior NLO candidates (SHG intensity >0.5 × AGS and band gap >3.0 eV). Remarkably, 1 and 2 melt congruently at 873.8 and 870.5 °C, respectively, which endows them with the potential of growing bulk crystals by the Bridgeman-Stockbarge method. This investigated system provides a new avenue for the structural evolution from layered CS to 3D NCS of NLO materials.     

Study of impurity induced modifications in amorphous N-type (GeSe3·5)100−x Bi x using high pressure technique

The technique of high pressure is utilized to study the carrier transport behaviour in doped and undoped bulk amorphous (GeSe_3·5)_100−x Bi _x (x=0, 2, 4, 10) down to liquid nitrogen temperature to observe impurity induced modifications in amorphous semiconductors. It is observed that pressure induced effects in lightly doped (2 at % Bi) and heavily doped (x=4, 10) semiconductors are markedly different. Results are discussed in view of the incorporation behaviour of the bismuth impurity.     

Further MN rule in thermally activated a.c. conduction of Se-Te-Sb chalcogenide glasses

Temperature and frequency dependence of a.c. conductivity have been studied in glassy Se₇₀Te_30−xSb_x (4 ≤ x ≤ 10) alloys. The observation of Further Meyer-Neldel rule in case of a.c. conductivity is reported. The observation of the correlation between Meyer-Neldel pre-factor σ₀₀ and Meyer-Neldel energy is explained by multiple excitations stimulated by optical phonon energy as described by Yelon and Movaghar.     

Microstructure change in Fe-based metallic glass and nanocrystalline alloy induced by liquid nitrogen treatment

The effects of acyclic liquid nitrogen(LN) treatment in a temperature range of -196℃ to 50℃ on the thermal and magnetic stability of Fe_(78)Si_9B_(13) and Fe_(73.5)Si_(13.5)B_9Nb_3Cu_1 glassy ribbons have been studied.The intrinsic heterogeneities of the metallic glasses can be activated through cryogenic thermal cycling,making irreversible structural changes after the treatment and inducing rejuvenation to the materials.The microstructural changes of both Fe-based metallic glass(MG) and nanocrystalline alloy induced by LN treatment were investigated. The experimental results show that the LN treatment could effectively rejuvenate the Fe-Si-B MGs and change their thermomechanical and magnetic properties. Based on the partially-crystallinity and well-known magnetic constants, the increase of the energy at the order of 10m J/g and magnetic domain wall movement and rotation at the order of 5-6 μm and 0.5°-0.8°are found for FINEMET-type amorphous alloy after LN treatment. It is also found that LN treatment can contribute a little stored energy to the magnetic domain wall movement and magnetic domain rotation.