紫外、深紫外非线性光学晶体的最新研究进展

深紫外相干光源对于光刻技术、光电子能谱仪、激光精密机械加工等均具有十分重要的意义。本文系统地阐述了可产生深紫外谐波光输出的非线性光学晶体的发现、基本线性、非线性光学性质，以及用它产生深紫外谐波光的方法。最后简介了深紫外谐波光的几个实例。     

深紫外非线性晶体KBe2BO3F2的倍频转换效率

深紫外(Duv)相干光源对于光刻技术、激光微加工、激光光谱仪等均具有重要的意义.KBe2BO3F2(KBBF)晶体是目前唯一可直接倍频产生深紫外激光的非线性光学晶体.本文通过分析KBBF晶体的光学倍频特性,分别得到了Nd:YV04激光2倍频、4倍频和6倍频以及Ti:Sapphire激光4倍频输出的相关技术参数;在此基础上,详细分析了KBBF晶体用于高斯光束的Ⅰ类和Ⅱ类倍频的转换效率.结果对于KBBF晶体用于产生深紫外全固态激光(DPL)的实验研究提供了重要的理论依据.     

新型深紫外非线性光学晶体KBe_2BO_3F_2族的研究进展

深紫外非线性光学晶体KBe2BO3F2(KBBF)发展至今,已有将近20年的历史。首先简单回顾了KBBF化合物的发现、晶体生长以及基本光学性质,同时对KBBF族(MBe2BO3F2,M=K,Rb,Cs)的其它化合物如:RbBe2BO3F2和CsBe2BO3F2的晶体生长和其基本光学性质进行了报道,然后对这些新晶体产生深紫外谐波光输出的能力做了评估,最后介绍了利用KBBF晶体器件产生的深紫外相干光源在先进仪器等方面的应用。     

紫外非线性光学晶体分子设计

紫外非线性光学晶体对全固态激光器的发展起着举足轻重的作用,对性能优秀的紫外非线性光学晶体的探索是光电功能材料领域的研究热点.如何在种类繁多的晶体材料中高效地搜索并获得结构优化的紫外非线性光学晶体,是当前该领域研究的关键问题.对非线性光学材料构效关系研究的发展历史进行了回顾,重点介绍了阴离子基团理论以及第一性原理方法在新型紫外非线性光学材料探索中的重要应用.材料计算模拟方法不仅能够较准确地预测紫外非线性光学晶体的关键光学参数,并可以定量和直观地分析其与晶体结构特征之间的内在关系.通过将理论模拟与结构搜索、化学合成、粉末倍频效应测试、单晶生长等实验手段紧密结合,建立了快速高效的非线性光学材料分子设计专家系统.具体的科研数据及成果显示,发展和完善这一基于分子工程学基础的专家系统,将能加快非线性光学晶体的研究步伐,提升其自主创新水平.     

新型紫外非线性光学晶体KNa5Ca5(CO3)8的合成、表征及性能的研究

采用水热法合成出一种新型碳酸盐非线性光学晶体材料KNa₅Ca₅(CO₃)₈, 该晶体属于六方晶系, 空间群为P63mc, 晶胞参数为a=b=1.00786(4) nm, c=1.26256(8) nm, Z=2。其晶体结构可以看作是由站立的[CO₃]基团连接相邻的两个[CaCO₃]_∞层, 从而沿[010]方向形成了四种不同类型的孔洞, 在这些孔洞中填充着K、Na 和[Na_0.67Ca_0.33]原子。KNa₅Ca₅(CO₃)₈晶体的粉末倍频效应为KDP的1.2倍, 且能够在可见光区实现相位匹配。紫外-可见-近红外漫反射光谱测试结果表明其晶体具有较大的光学带隙, 大概为5.95 eV, 是具有潜在应用前景的紫外非线性光学晶体材料。此外, 第一性原理的计算结果表明, 晶体的非线性系数主要来源于CO₃基团。     

我科学家发现一种新型光学晶体

《自然》杂志以《中国藏匿的晶体》为题，用3页篇幅对中科院理化技术研究所陈创天院士率领的团队发现并生长出一种最新的光学晶体——氟代硼铍酸钾（KBBF）晶体进行了详细报道，并称“中国实验室成为这种具有重大科学价值的晶体的唯一来源，它表明中国在材料科学领域实力日益增强”。KBBF晶体是目前唯一可直接倍频产生深紫外激光的非线性光学晶体，是在非线性光学晶体研究领域中，     

硼镀酸盐非线性昌体材料研究取得新发现

获得大的非线性光学系数、合适的双折射率、以及优良的物理化学性能的深紫外非线性光学晶体具有很强的挑战性,碱金属硼酸盐由于其具有优异的深紫外透光性能而成为深紫外非线性光学晶体材料的研究热点。     

非线性光学晶体三硼酸铋的拉曼光散射

结构分析表明非线性光学晶体三硼酸铋BiB3 O6的晶胞参数为a1=0 .7116nm ,a2 =0 .4993nm ,a3 =0 .65 0 8nm ,β =10 5 .62° ,每个初基晶胞含有二个分子。在不同几何配置下的激光拉曼光谱观察到了晶体中硼氧四面体和硼氧三角形的特征晶格振动和振动模的分裂。拉曼光谱表明晶体的内部结构有很强的各向异性 ,这就是晶体非线性光学性质的来源     

新型红外波段非线性光学晶体材料研究通过验收

中科院福建物构所主持的“新型红外波段非线性光学晶体材料研究”项目通过了专家的验收。该项目组针对非线性光学晶体材料发展前沿领域,开展了红外波段非线性光学晶体材料探索研究,取得了一系列创新性研究进展。他们合成了数种在中红外区透过的新型硼铌酸盐化合物,粉末非线性倍频系数为6．8-20倍KDP,采用助溶剂法研究了晶体生长。合成了数种中远红外透过的新的硫属化物,在空气中可稳定存在至700℃,初步粉末倍频效应测试表明,该类硫属化物具有非线性光学效应。     

Femtosecond Z-scan measurements of nonlinear refraction in nonlinear optical crystals

We report an investigation of third-order optical nonlinearities in several nonlinear optical crystals using the Z-scan technique with femtosecond laser pulses at 780 nm wavelength. The crystals studied include LiNbO₃:MgO, KTiOAsO₄, KTiOPO₄, β-BaB₂O₄ and LiB₃O₅, which are extensively used for ultrashort-pulse second-harmonic generation and optical parametric oscillation. The nonlinear refractive index n₂ in these crystals has been determined to be in the range from 10⁻¹⁶ to 10⁻¹⁵ cm²/W. No two-photon absorption has been observed. The experimental results are compared with the two-band model for the bound electronic Kerr nonlinearity. It is shown that the measured n₂ values in β-BaB₂O₄ and LiB₃O₅ are one order of magnitude smaller than those of LiNbO₃:MgO, KTiOAsO₄, KTiOPO₄, which is in agreement with the theoretical prediction.     

New opportunities for ferroelectric deep-UV nonlinear optical crystals

<正>Deep-ultraviolet (deep-UV) light with the wavelength below200 nm is one of the most crucial elements of both laser-driven industrial and scientific applications in recent years [1]. DeepUV light has been produced using a variety of techniques, such as gas discharge lamps, synchrotron radiation, excimer lasers,free electron lasers, and nonlinear frequency conversion.     

Microhardness studies on nonlinear optical L-alanine single crystals

Vickers and Knoop microhardness tests were carried out on grown L-alanine single crystals by slow evaporation technique over a load range of 10–50 g on selected broad (2 0 3) plane. Vickers (H _v ) and Knoop (H _k ) microhardness for the above loads were found to be in the range of 60–71 kg/mm² and 35–47 kg/mm², respectively. Vickers microhardness number (H _v ) and Knoop microhardness number (H _k ) were found to increase with increasing load. Meyer’s index number (n) calculated from H _v shows that the material belongs to the soft material category. Using Wooster’s empirical relation, the elastic stiffness constant (c ₁₁) was calculated from Vickers hardness values. Young’s modulus was calculated using Knoop hardness values. Hardness anisotropy has been observed in accordance with the orientation of the crystal.     

Dispersion of the nonlinear refractive index of optical crystals

The nonlinear refractive indices of several important optical materials have been measured at the second and third harmonic wavelengths of the Nd laser using nearly degenerate four-wave mixing. Measurements made relative to the nonlinear index of fused silica have the highest accuracy. Absolute measurements were also made using the Raman cross-section of benzene as a nonlinear reference standard. The relative measurements are compared with a despersion model base on parameters fitted to the linear refractive indicies and also to a recently proposed model based on Kramers-Kronig transformation of the calculated, two-band, two-photon loss spectrum.     

Growth and characterization of nonlinear optical diglycinehydrobromide single crystals

Diglycinehydrobromide (DGHB) a semi-organic nonlinear optical material with the molecular formula C₄H₁₁N₂O₄⁺Br⁻ has been synthesized at ambient temperature. Chemical composition of the synthesized material was confirmed by CHN analysis. Functional groups present in the sample were identified by FT-IR and Raman spectral analysis. Bulk single crystals of DGHB were grown by slow evaporation method at constant temperature. Powder X-ray diffraction pattern of the grown DGHB has been indexed. Unit cell parameters of the grown DGHB crystals were determined. Thermal stability of DGHB was determined from TGA/DTA and DSC response curves. Mechanical hardness of the grown crystal DGHB was determined and Vickers hardness number was calculated. The optical transparency and the lower cutoff of UV transmission were identified from the recorded UV-vis-IR spectrum of DGHB. The Kurtz powder second harmonic generation test shows that the crystal is a potential candidate for optical second harmonic generation.     

New nonlinear optical crystals: Strontium and lead tetraborates

The nonlinear-optical and electro-optical properties of the crystals of strontium (SrB₄O₇) and lead (PbB₄O₇) tetraborate are investigated. The transparency range of this crystals is 130–3200 nm for SBO and 235–4000 nm for PBO. The effective nonlinear coefficient and surface optical damage threshold of the SBO is higher than for any borate crystals. The SHG phase-maching conditions in these crystals are absent. The possible application of these crystals is discussed.     

Salient features of recording of the optical rectification signal from nonlinear optical crystals

Analysis and derived formulas were employed to examine the salient features of the process when the current and voltage due to optical rectification in crystals were used to measure the electric parameters of continuous, pulsed, and pulsed-periodic lasers, with allowance for spatial dispersion. The errors of measurement were evaluated. Meters based on optical rectification show promise for use in laser fusion facilities and for measuring the efficiency of harmonic generation. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 8–14, May, 1997.     

A novel growth method for organic nonlinear optical crystals

A novel crystal growth method called seed-orientated undercooled melt growth is proposed for growth of organic nonlinear optical (NLO) crystals. The main advantage of this method is that organic NLO crystals can be grown along a given direction and the optional crystal faces (h k l) may be grown directly in a crystallizer. The grown crystals with determinate crystal faces are possible to apply as nonlinear optical devices regardless of subsequent cutting and polishing. Using this method, the different crystal faces of benzophenone crystals were successfully grown in a quartz crystallizer, and the orientation of the grown crystal faces were measured by an X-ray angular instrument.     

纯介质光子晶体非线性效应研究进展

如何在低阈值小尺度(毫瓦或皮焦量级、微米以下)情况下激发非线性光学效应是近年来光学领域研究的重要课题。该研究最直接的应用需求就是光子集成芯片,这是未来实现超高速、大容量信息网络体系的基础。光子晶体具有类似于半导体能带的光子禁带(PBG),被誉为“光子半导体”,为人们提供了一种新颖而又实用的操纵光子的物理手段,使低阈值、可集成非线性效应产生成为可能。越来越多的非线性效应在光子晶体中已经被发现,例如光子晶体慢光、带隙孤子、电磁感应透明、二次谐波产生、光学双稳态等,本文将着重对可用于光子集成器件开发的光子晶体非线性效应研究领域的一些主要成果和进展进行总结,介绍其相关应用并对光子晶体非线性效应研究作出展望。