ORGANIC NONLINEAR OPTICAL CRYSTAL:N-(4-NITROPHENYL)-(s)-(+)-2-PYRROLIDINEMETHYLENE TOSYLATE(NPP-OTs)

Large crystal NPP-OTs has been obtained by growth from solution,its powder SHG efficiency is 1/3 of urea.It shows it is a new convenient approach to obtain organic second-order NLO crystal:the dipole-dipole interaction is oppos- ed by introducing a large side group.

New Complex Nonlinear optical Crystal-Bis(4-methoxybenzaldehyde thiosemicarbazone) Zinc Chloride(ZnL_2Cl_2)

The structure of ZnL2Cl2 (L=4-methoxybenzaldehyde thiosemicarbazone) has beenobtained by x-ray diffraction. The compound crystallized in space group Cc with Z=4, in a unit cellof dimensions, a=9.08909(10), b=22. l420(10), c=11 .7890(l0)A,β=90.050(10)°, v=2374.6(12)A3,Dc=1 .552gcm-3. H=1 .463mm-1. R=0.0338. and Rw=0.0418. The structure contains individualZnL2Cl2 distorted tetrahedral units in which L molecules are S-bonded as monodentate to the metalions; chloride ions are also coordinated. The nonlinear optical properties of the zinc complex arealso presented in this letter.

Evaluating refractive index and birefringence of nonlinear optical crystals:Classical methods and new developments

Nonlinear optical(NLO)materials play an increasingly important role in laser technology.Birefringence is one of the most important parameters for NLO materials to realize angle phase-matching conditions.In comparison with other desirable optical properties,the availability of birefringence and refractive index dispersion is especially problematic owing to the strict requirements for single crystals.In this review,we described how to obtain the refractive index and birefringence of NLO materials from crystals sub-millimeters to centimeters in size.Espe-cially,recently developed methods including the minimum deflection angle method,auto-collimation method,prism coupling method,oil immersion technique,interference color method,and theoretical calculation(DFT)for rapid assessment of birefringence are summarized,the contents of which are mainly focused on the principles and typical applications,together with the advantages and drawbacks.In addition,representative examples of bire-fringent measurements were presented.The purpose of this work is to provide a useful perspective on the characterization of birefringence for NLO materials.It is hoped that this review can give a clear description of the birefringence measurements and accelerate the discovery of new NLO crystals.

Ultraviolet Nonlinear Optical Crystals inπ-Conjugated System

UV nonlinear optical(NLO)crystals are essential materials for UV solid state laser output.To date,frequency conversion in UV region is mainly dependent on borates with planar BO3 or B3O6 units.Since the practical applications require more and more high comprehensive properties of crystals,it is urgent to develop new UV NLO crystals.However,it is more and more difficult to find new borate NLO crystals because borate NLO crystals have been studied for several decades.Therefore,it is important to search new systems for the exploration of UV NLO crystals.Based on the relationship between the microstructure and properties of the groups,we proposed that inorganic(CO3)2-and(NO3)-groups can be as new NLO active units for UV NLO crystals because they haveπ-conjugated configuration.Accordingly,our group have performed related work in carbonate and nitrate systems in recent years,which resulted in finding some excellent carbonates and nitrates NLO crystals.In addition,we have recently expanded the research field from inorganic to organicπ-conjugated systems,such as isocyanurates.This mini review will introduce the research results of our team in the field of UV NLO crystals including carbonates,nitrates and cyanurates in recent years.

Properties of second harmonic generation in nonlinear optical crystals CsLiB_6O_(10) and K_2Al_2B_2O_7

The phase-matching for nonlinear optical crystal, the nonlinear phase matching angle, effective nonlinear coefficient, walk-off angles, permitted angle, and permitted wavelength are obtained in type-I and type-II phase matching in ultraviolet （UV） nonlinear optical crystals CsLiB6O10 （CLBO） and K2Al2B2O7 （KABO） by detailed theoretical simulation. Through analysis and comparison, the phase matching characteristics of the second harmonic generation in the crystals are discussed when the wavelengths of the basic frequency lights turn continually.

Research progress on mid-IR nonlinear optical crystals with high laser damage threshold in China

Nonlinear optical(NLO)crystals have been playing an increasingly important role in laser science and technology.The NLO crystals used in the middle infrared(mid-IR)region,compared with the NLO crystals in the other wavelength regions,are still not good enough for the application of high-energy laser.The main defect is that their laser damage thresholds(LDT)are low.Chinese scientists have made a lot of important contributions to the UV and visible NLO crystals.In the last decade,they also did a lot of work on the mid-IR NLO materials.The main purpose of these researches is to increase the LDT and simultaneously balance the other properties.This paper presents a brief summary of their research progress in this topic on three types of materials:chalcogenides,oxides,and halides.The emphasis is put on the design strategy and quality control of the crystals.

Influence of Metallic Substitutions on the Optical and Mechanical Properties of NLO Benzoyl Glycine Crystals

Benzoyl glycine （BG） is a promising organic nonlinear optical （NLO） crystal, whose second harmonic generation （SHG） efficiency is much higher than that of KDP （potassium dihydrogen phosphate）. Single crystals of pure, Cu2＋ and Cd2＋ doped BG were grown by slow evaporation technique. Optically transparent and defect free single crystals of size up to 10 mm×15 mm×10 mm were harvested in a period of 40-60 days. The growth conditions of pure and doped crystals of BG were optimized and the grown crystals were confirmed by single crystal XRD （X-ray diffraction）. The grown crystals were characterized by FTIR （Fourier transform infrared spectroscopy）, optical absorption and microhardness studies. The microhardness studies confirm that BG has a moderate VHN （Vickers hardness number） value in comparison to the.other organic NLO crystals. The efficiency of frequency doubling was measured for the using Nd：YAG laser and the results were discussed.

Structure and Nonlinear Optical Property of the Cluster Compound V_2S_6O_2Cu_6(3-MePy)_6

A cluster compound V2S6O2Cu6（3-MePy）6（3-MePy = 3-methyl pyridine） has been synthesized by using skiving method and the crystal structure was characterized by X-raydiffraction： space group P1, Z = 1, a = 9.7278（4）, b = 10.4180（5）, c = 11.9230（6） , α = 108.240（3）, β = 98.120（2）, γ = 99.500（2）o, R = 0.052 and wR = 0.104. The NLO properties were studied by Z-scan technique with 8 ns pulsed laser at 532 nm. The cluster exhibits strong NLO absorptive ability（α2 = 1.7 × 10–10 m·W–1） and effective self-focusing performance（n2 = 1.27×10–18 m2·W–1） in a 1.58 × 10–4 mol·dm–3 DMF solution.

Generation of femtosecond laser pulses at 263 nm by K_3B_6O_(10)Cl crystal

The third harmonic generation（THG） of a linear cavity Ti：sapphire regenerative amplifier by use of a K3B6O（10）Cl（KBOC） crystal is studied for the first time. Output power up to 5.9 mW is obtained at a central wavelength of 263 nm,corresponding to a conversion efficiency of 4.5% to the second harmonic power. Our results show a tremendous potential for nonlinear frequency conversion into the deep ultraviolet range with the new crystal and the output laser power can be further improved.

Generation of femtosecond laser pulses at 396 nm in K_3B_6O_(10)Cl crystal

K3B6O10Cl （KBOC）, a new nonlinear optical crystal, shows potential advantages for the generation of deep ultraviolet （UV） light compared with other borate crystals. In this paper we study for the first time the second harmonic generation （SHG） of a femtosecond Ti：sapphire amplifier with this crystal. Laser power is obtained to be as high as 220 mW at the central wavelength of 396 nm with a 1-mm-long crystal, and the maximum SHG conversion efficiency reaches 39.3%. The typical pulse duration is 83 fs, The results show that second harmonic （SH） conversion efficiency has the room to be further improved and that the new nonlinear crystal is very suited to generate the high efficiency deep ultraviolet laser radiation below 266 nm.

β-BaB_2O_4 with special cut-angle applied to single crystal cascaded third-harmonic generation

High-efficiency single crystal cascaded third-harmonic generation（THG） was realized in β-BaB_2 O_4（BBO） material with special cut-angle. By analyzing effective nonlinear optical coefficient（deff） of the cascaded THG process, which was composed by type-II frequency doubling and type-I sum-frequency, the optimum phase matching（PM） direction in BBO crystal was determined to be（θ = 32.1？, φ = 11？）. With an optimized 9-mm long sample which was processed along this direction, the highest cascaded THG conversion efficiency reached 42.3%, which is much superior to the similar components reported previously, including ADP, KDP, and Gd_x Y_（1-x） COB crystals.

Fluorooxoborates:A precious treasure of deep-ultraviolet nonlinear optical materials

As the key components of all-solid-state deep-ultraviolet(DUV,λ<200 nm)laser sources,exploring DUV nonlinear optical(NLO)materials has been a research hotspot for a long time.However,as the only material that has been practically used to generate DUV coherent light through the direct second harmonic generation(SHG)process,KBe_(2)BO_(3)F_(2)(KBBF)still meets bottlenecks,namely,severe layered crystal growth tendency,for extensive application.In the search for the next generation of DUV NLO materials,fluorooxoborates are highly expected due to their excellent NLO performances,flexible structures,and rich structural chemistry.So far,a large number of materials with prominent properties have emerged in the fluorooxoborate system.By investigating the differences in structures and properties among fluorooxoborates and borates and borate fluorides,the excellent NLO per-formances of fluorooxoborates are attributed to functionalized B-O/F chromophores.In this review,by analyzing the published fluorooxoborates,the fluorooxoborate system is a precious treasure for exploring DUV NLO ma-terials.The synthesis,structures,and properties of some representative fluorooxoborates in the research history are introduced and summarized.Finally,we put forward the opportunities and challenges of future research in fluorooxoborate DUV NLO crystals.

掺锶的偏硼酸钡(Sr_xBa_(1-x)B_2O_4)大块单晶的生长和表征

Barium metaborate (BaB 2O 4) exists in two forms the high temperature for m α phase and the low temperature form β phase,with the phase transition poi nt at around 925℃.The low temperature phase (β BBO) is an excellent NLO cryst al for UV region,while the high temperature one (α BBO) is known as a good bir efringent material.α BBO crystal possesses better transparency in the ultravio let region compared with commonly used YVO 4 and CaCO 3 crystals.However,due t o phase transition problem,it is difficult to grow single α BBO crystals by D CZ method,which restricts its wider application.α BBO crystal usually cracks upon cooling resulted from phase transition to β phase.Therefore,it is difficult to grow β BBO single crystals directly from pure BaB 2O 4 mel t;however,to grow single crystals of α BBO is not easy,either. Our recent experiments showed that one could avoid cracking of α BBO cryst als by Sr 2+ doping.This minute amount of Sr 2+ plays the role of structure stabilizer,which inhibits structural reconstruction. In this way,Sr 2+ d op ed BBO single crystals do not subject to phase transition from 925℃ down to roo m temperature. We have mow successfully grown out α BBO single crystals 30mm in diameter by D CZ method from Sr x Ba 1- x BO 4 melt with Sr concentration 0.3 0 .5%.The ratation rate is 10 15r/min,pulling speed is 1 2mm/h.Preliminary tests revealed that its structure and physic chemical properties were almost identic al to those grown from pure melts.These Sr 2+ doped α BBO crystals are no w being widely used in optical isolators.

功能晶体材料CMTD生长动力学和结晶习性的研究

Process of crystal growth can be controlled by both surface kinetics and by volume transport as well.Although the complicated relation between the surface kinetics and volume transport exsits,generally,they are studied seprately.Due to the mathematical complexity of heat and mass transport equations,the in depth studies of heat and mass transport process become difficult.Most of the studies on the transport were performed for the growth from melt.Most of the work on Surface kinetics has been done for crystal growth from aqueous solution because the in situ observation of crystal growth is easily carried out.In recent years,the surface kinetics studies on the nanometer scale,even atomic scale,are demonstrated by using AFM.

阴离子杂质对KDP晶体生长习性的影响及快速生长研究

Great interest is being focused on the growth technique of KDP crystal,the first choice material for the fabrication of frequency converter and electro optic switcher used in the studies of inertial confinement fusion (ICF).To reduce the cost of growth,scientists are endeavoring to promote the growth rate.The“point seed” method is one of rapid growth techniques recently developed by Lawrence Livermore National Laboratory.In the former technique,crystals are grown in all three directions at an averaged rate of 10 15mm/day. Impurities are regarded as one of the factors to inhibit the growth rate.It is generally accepted that high valence cationic ions,such as Fe 3+ ,Cr 3+ ,Al 3+ ,etc,are easy to be adsorbed on the prismatic faces and inhibit their growth.Some anions,especially those have ability to form strong hydra bond,such as phosphate derivatives (polyphosphate,metaphosphate,pyrophosphate,etc) have significant inhibiting effects on the growth of KDP pyramidal face.It is suggested that the H bonding is the key interaction force between the growing surface and the impurities.

熔盐法生长Ca_4GdO(BO_3)_3单晶

Ca 4GdO(BO 3) 3 (GdCOB) single crystal is a new nonlinear optical crystal whi ch was discovere d in recent years.It has a large effective nonlinear optical coefficient,a high damage threshold,good chemical and physical properties and insensitivity to moi sture.Its moderate birefringence is favorable for phase matching.These propertie s make it possible to obtain frequency doubling laser of 1.064μm.By doping,it may be a excellent self frequency doubling crystal.Transparent single crystals GdCOB as needle were grown by the flux method. Chemical compounds Gd 2O 3,CaCO 3,B 2O 3 and H 3BO 3 were used as starti ng materials.By many experiments,with different ratio,it is proper to mix the st arting materials according to the reaction Gd 2O 3+8CaCO 3+6H 3BO 3=2 Ca 4 G dO(BO 3) 3+8CO 2+9H 2O.PbO was used as the main flux ,adding moderate PbF 2 , and B 2O 3.B 2O 3 also can be used as initial compounds and it is also a goo d solvent,but at high temperature,it has heavy viscousness.The crystals grown fr om B 2O 3 commonly has inclusion,so we used H 3BO 3 instead of B 2O 3.At t he same time,we considered that at high temperature H 3BO 3 will be decomposed and evaporated,which would make the initial composition change.When proper B 2 O 3 was added,it not noly can be used as solvent,but also can stabilize solvent component.The melt was contained in a platinum crucible.After holding the melt 1200℃ for 24h,it was cooled at a rate of 0.5℃ per hour.Single crystals GdCOB were obtained.With microscope,we observed the crystals have defects such as inc lusion and bubbles,which are related to rapid cooling,imperfect melt transport a nd unstable temperature.

非线性光学晶体K_(3.0)Li_(2.0)Nb_(5.0)O_(15.0)的生长

Potassium lithium niobate single crystal with a dimension of 20mm×15mm×30mm was grown by EFG technique in our laboratory.Compared with Czochralski method for the growth of KLN crystals,EFG technique possesses the following merits.Crack of crystals can be weakened during the lowering of temperature and the crystals free of crack can be obtained.The crystals have no rotation,the growth striation caused by the rotation of the crystals can be eliminated.With action of capillary from a die hole,the convective effect of melt at solid liquid interface can be reduced,therefore the homogeneity of crystals is better than that of crystals obtained by Czochralski method.The growth striation parallels each other and is perpendicular to the growth direction,so the good blue SHG can be obtained when ground wave goes through the KLN crystals.Since capillary force does not fully counteract the convective effect,the inhomogeneity of crystals can’t completely be eliminated.The low SHG conversion efficiency of KLN crystals is mainly caused by inhomogeneneity of crystals.For the growth of incongruent melting crystals,the growth rate is limited by the rejection of impurity,this also makes homogeneity of composition become bad.In the growth of KLN crystals by EFG technique,the fluctuation of the temperature at solid liquid interface should be enough small,and the film thickness of melt should be proper.Too thick film of melt makes the process of crystal growth unstable;too thin film of melt can lead to the constitutional supercooling.

新型深紫外非线性光学晶体的探索

Based on anionic group theory,a computer assisted nonlinear optical(NLO)crystal design system has been developed.This method has proved to be a highly efficient means of discovering NLO crystals.With the help of this system,a series of new borate crystals,like as KBe 2BO 3F 2(KBBF),Sr 2Be 2B 2O 7(SBBO),Ba 2Be 2B 2O 7(SBBO),BaAl 2B 2O 7(BABO)and K 2Al 2B 2O 7(KABO)have been discovered.Among them KBBF possesses the shortest SHG wavelength output,SBBO has the largest SHG coefficient and KABO is found to have the best optical homogeneity and easy to grow out large size of the crystal.The investigation showed that KABO is a promising NLO crystal for 4 th and 5 th harmonic generations of Nd∶YAG laser.

非线性光学晶体电光快速调谐光参量器件的研制

Optical parametric lasers widely using in many science and technology field owin g to its merit of wide tunable spectrum range.But common optical parametric lase rs achieve tune by change of angel or temperature.The tune velocity and tune pre cision of these tune modes does not satisfy in many applications.The reporting i nto an optical parametric laser which achieve tune by electooptic effect,that have got speediness tune velocity and relatively quite tune precision. The optical parametric device design based on parametric fluorescent produce thr ough sum frequency phase matching in nonlinear optical crystals.It is a tune pr o cess of refractive index about parametric and pump light in nonlinear optical cr ystals namely.But refractive index of nonlinear optical crystals possess electro o ptic effect can change via apply transformable electro field.This change only w a nts a time of ns grade.So optical parametric device with nonlinear optical cryst als possess suitability electrooptic effect can realize speediness tune in princ iple.The idea about design on the recommended device here is somewhat as follows .The tune model is phase tuning.To strive increase the effect of electro optic f unction under keep immovable polarization directions of 3 wavelength in the opti cal parametric process,to strive convenient for apply electro field,the electro field is only sensitive for a refractive index of some wavelength in specificall y spectrum region.The principium examination has showed that the idea is reasona ble.Our count have show also that its tune precision same as expectance.