Electro-Optic and Second Harmonic Generation Materials, Devices, and Applications

Tunable long-wavelength interdiffused quantum-well photodetector

Alex Siew-Wan Lee, E. Herbert Li

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A wide tunable long-wavelength AlGaAs/GaAs quantum well intersubband photodetector is theoretically analyzed for various stages of interdiffusion. Both the absorption strength and responsivity are enhanced for certain extents of interdiffusion and the peak detection wavelength can be red shifted continuously over a large tunable range. The dark current increases with interdiffusion but is acceptable for smaller diffusion extent.

Picosecond z-scan investigation of two-photon absorption and bound electronic self-focusing in second-harmonic generation crystals

Wei Ji, He Ping Li, Feng Zhou, et al.

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We present our investigation of two-photon absorption and self-focusing in second-harmonic-generation crystals on a picosecond 532-nm-wavelength beam using the z-scan technique. By measuring the crystal transmittance as a function of the crystal position with respect to the focus, the two-photon absorption coefficients were determined to be 0.041 plus or minus 0.008, 0.10 plus or minus 0.02, and 0.24 plus or minus 0.06 cm/GW for KTPA, KTA, and LiNbO₃, respectively. With inserting an aperture in front of the detector that recorded the transmitted laser pulse energy, self-focusing effects manifested themselves in the z scans on the three crystals at input irradiances of higher than a few GW/cm². The quantitative data confirm that the optical Kerr nonlinearity should be responsible for the observed self-focusing and n₂ equals (4.6 plus or minus 0.9), 3.6 plus or minus 0.7), and 5.3 plus or minus 1.0) multiplied by 10^-6 cm²GW in KTP, KTA and LiNbO₃, respectively. The microscopic origin of the measured n₂ can be understood in terms of bound electronic effects. The theoretical predictions are in agreement with our measurements. Finally, effects of the observed refractive nonlinearity on laser-induced damage are discussed.

Diode laser-pumped 1129-nm laser in Nd3+ doped Sr5(PO4)3F

Xin Xiong Zhang, W.-L. Zhou, Pin Hong, et al.

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A low-threshold, efficient diode-pumped 1129 nm laser has been demonstrated for the first time using Nd³⁺ doped Sr₅(PO₄)₃F. More than 50 mW of yellow laser output at 564.5 nm has been generated based on this laser transition.

All-optical logical gates with bacteriorhodopsin films

Devulapalli V. G. L. N. Rao, Francisco J. Aranda, Desai Narayana Rao, et al.

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The photochromic protein bacteriorhodopsin (bR) obtained from the purple membrane of the halocbacterium halobium has attracted considerable amount of interest recently. Several applications in photonics technology have already been proposed. bR lends itself to structural alterations at the molecular level by use of bioengineering and chemical synthesis methods. It is very stable under hard environmental conditions of temperature, salinity, etc. The films that were used in our experiments are stable over a period of four years. The lifetimes of some of the intermediate states of bR photocycle can be altered over a wide range by genetic manipulations of some of the amino acids that compose the bR membrane or by controlling the pH of the host materials. All of this makes bR a very attractive material for applications in optical computers and information processing. We present a technique that utilizes the molecular states of a bR thin film to implement an all-optical switch and all-optical logic AND and Or gates. A two-color backward degenerate four-wave mixing geometry with wild-type and chemically stabilized films of bacteriorhodopsin constitute the experimental setup. The saturation intensity, sensitivity and excited state lifetime (M state lifetime) of the films are very different. We use red light to form a holographic grating,due to the B to M transition and blue light to form a grating due to the fast photochemical transition from.M to B. Each of the two wavelengths in the experimental system acts as an input to the all-optical gates and the phase conjugate signal beam is the output of the gates.

Physical and optical properties of sputtered lithium niobate thin films

Dexin X. Lu, Emile M. W. Wong, Edwin Y. B. Pun, et al.

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LiNbO₃ thin films were deposited by rf magnetron sputtering using LiNbO₃ ceramic targets on z-cut single crystal LiTaO₃ substrate. The as-deposited thin films were annealed at 550 degrees Celsius to 650 degrees Celsius for 60 min in oxygen ambient. The results of x-ray diffraction indicate that the dominant orientation of the sputtered LiNbO₃ thin film is (202). The transmittance spectra of LiNbO₃ thin films annealed at different temperatures were measured and compared with that of bulk single crystal substrate (the measured wavelength range is from 300 nm to 800 nm). The transmittance drops down to about 10% at 300 nm wavelength and has a value of 70 to approximately 80% at 800 nm wavelength.

Growth and properties of some KTP family crystals

Jiyang Wang, Jingqian Wei, Yaogang Liu, et al.

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Crystal growth of KTiOPO₄(KTP) family with flux method has been summarized. The results of defect observation with synchrotron radiation topography and other methods have been reported. It is shown that KTP crystal is of high-quality and there exist different kinds of defect such as growth striations, multiple domains in doped KTP and KTA crystals. The observation and discussion about the bicrystal of KTP family crystal have been mentioned in the paper. SHG and SFG measurements indicated that KTP family crystals investigated have excellent nonlinear optical properties.

White-light emission from water soluble C60 derivative

Haosheng Fei, Li Han, Linsong Li, et al.

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A water soluble C₆₀ derivative, (TPA⁺)₃C₆₀^3-(OH)_n, have been synthesized by means of electrochemical method firstly, and very broad 'white light' spectrum from this derivative has been observed. The bright white light emission of the new material results from a perturbation to the normal C₆₀ molecule due to the Jahn- Teller distortion of symmetry structure and the interaction between C₆₀^3- and (OH)_n.

Growth of a new electro-optic crystal-DCNP

Changshui Fang, Lixiong Fang, Hongsheng Zhuo, et al.

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This paper reports on the growth of 3-(1,1-dicyanothenyl)-1- phenyl-4,5-dihydro-1H-pyrazole(DCNP) crystals in dimethylformamide. The effect of different solvents on the growth of DCNP has been investigated. Dimethylformamide was found to be a good solvent. Transparent DCNP single crystals were grown from this solvent. They are a promising electro- optic material.

Characteristic recognition system with artificial neural network

Shizhe Shang, Jun Liu, Yunshen Zhang, et al.

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The optical recognition system is based on the optical characteristic extractor. In this report, a kind of new theory of the characteristic recognition system with artificial neural network is introduced. The optical compound eye system, lateral inhibition network and back propagation network (BP) are adopted to form a parallel neural network, recognition system. The field of view is divided into mosaic pixels by the plane compound eye lens, which is convenient to use single photoelectric detector. The information received by the detector is extracted characteristic through the lateral inhibition network. It is a parallel neural network made up of resistor network and it has the advantage of high speed, simple structure, etc. BP network is used for pattern recognition. Its weights are anew distributed during network learning processing. Once the studied object is detected again, the system will quickly response its pattern. In this paper, several experimental data of simple patters are given, and the precessions of the network recognition are analyzed. Finally, it is pointed out that the characteristic recognition system is feasible in applying to industrial detection and Chinese character recognition, etc.

Studies on the H-aggregation in hemicyanine Langmuir-Blodgett films

Xingze Lu, Kui Han, Shihong Ma, et al.

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We investigated the effects of deposition parameters, subphase additions and annealing on the optical linear (absorption) and nonlinear (second harmonic generation) properties of hemicyanine (HEM) Langmuir-Blodgett (LB) films via aggregate status variations. HEM molecules formed H- aggregates in LB films, characterized by a blue-shift of the absorption band relative to the monomeric spectra, leading to a reduction of the effective hyperpolarizability beta due to the second harmonic off-resonant effect. The spontaneous aggregation mainly occurred during compression on the Langmuir trough. The degree of H-aggregate could be reduced and beta could be enhanced by raising the compressional speed and/or lowering the deposition surface pressure. By adding KI in the subphase, the observed beta-enhancement and absorption band red-shift in HEM LB monolayers were attributed to H-aggregate dissociation and intramolecular charge transfer. The time-resolved fluorescence profiles of HEM LB multilayers showed that there mainly existed two species (monomer and dimer) with characteristic decay times in the order of 100 ps and 10 ps, respectively.

Flow dichroism in Langmuir-Blodgett multilayers

Xingze Lu, Kui Han, Guangpeng Zhou, et al.

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Optical linear (polarized UV-visible absorption) and nonlinear (rotation-angle second harmonic generation) measurements on Y-type hemicyanine/arachidic acid interleaving Langmuir-Blodgett multilayers verified that the dipping-induced in-plane molecular alignment was enhanced with increasing dipping speed or layer number. We gave the first direct evidence for the interlayer-enhancement of flow orientation in LB multilayers.

High-order anisotropic conical diffraction in doped KNSBN crystals

Yongyuan Jiang, Yan Li, Zhongxiang Zhou, et al.

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With two extraordinary polarized beams incident on doped KNSBN crystals, higher diffraction orders have been observed when an external electric field is applied. At the same time, high-order anisotropic diffraction cones can also be observed on the viewing screen. These cones are originated from photorefractive four wave mixing which involves incident beams, high-order diffracted beams and forward scattered beams satisfying the phase matching condition. We also investigated the dependence of higher diffraction orders on incident angle.

Burstein shift and UV photoresponse in IBAD-deposited transparent conducting ZnO films

Deheng Zhang, Ruwei Gao, Honglei Ma

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A Burstein-Moss shift has been observed in highly transparent conducting zinc oxide (ZnO) films prepared by ion-beam assisted reactive deposition (IBAD). The optical gaps ranged from 3.27 to 4.1 eV increase with an increase in film conductivities and carrier concentrations. An over 773 K annealing reduces conductivities by several orders of magnitude and subsequently narrows the optical gaps from 3.41 to 3.24 eV. When the films are irradiated with a UV light, they exhibit some photoresponse. The observed UV photoresponse can be interpreted using oxygen photodesorption and chemisorption at the surface.

Efficient optical nonlinear Langmuir-Blodgett films: roles of matrix molecules

Shihong Ma, Xingze Lu, Liying Liu, et al.

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A novel bifat-chain amphiphilic molecule nitrogencrown (NC) was adopted as an inert material for fabrication of optical nonlinear Langmuir-Blodgett (LB) multilayers. Structural improvement in the Z-type mixed fullerene derivative (C₆₀-Be)/NC LB multilayers samples was realized by insertion of the C₆₀-Be molecules between two hydrophobic chains of the NC molecules. The relatively large third-order susceptibility (chi) ⁽³)xxxx(- 3(omega) ;(omega) ,(omega) ,(omega) ) equals 2.9 multiplied by 10^-19 M²V^-2 (or 2.1 multiplied by 10^-11 esu) was deduced by measuring third harmonic generation (THG) from the C₆₀-Be samples. The second harmonic generation (SHG) intensity increased quadratically with the bilayer number (up to 116 bilayers) in Y-type hemicyanine (HEM)/NC interleaving LB multilayers due to improvement of the structural properties by insertion of the long hydrophobic tail of HEM molecules between two chains of NC molecules. The second-order susceptibility (chi) ⁽²)zxx(-2(omega) ;(omega) ,(omega) ) equals 18 pM V^-1 (or 4.35 multiplied by 10^-8 esu) was obtained by measuring SHG from the HEM samples. The NC molecule has attractive features as a matrix material in fabrications of LB multilayers made from optically nonlinear materials with hydrophobic long tails or ball-like molecules.

Excitons in novel quantum materials: a Monte Carlo study

En-Ge Wang

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The exact binding energies of excitons in novel type-II In_1-xGa_xAs/GaSb_1-xAs_y quantum well materials in the effective mass model are evaluated by diffusion quantum Monte Carlo simulations. The results support the experimental interpretation that a stable excitonic ground state can exist in spatially separated electron-hole systems. The electron(hole) correlation effects and quantum confinement are shown to enhance the binding of the excitons. The calculated results for various magnetic fields provide a guide for further experiments in accurate determination of the binding energies, which is important in the optoelectronic application of novel quantum well materials.

Blue light-emitting diodes from polymer blends

Jingsong Huang, Haiyan An, Jingying Hou, et al.

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Electroluminescence (EL) is reported from a novel polymer blend of poly(2,5-dibutoxyphenylene) (PPP) and polymer poly(N-vinylcarbazole) (PVK). Since PPP and PVK are soluble in common organic solvents, light-emitting diodes (LEDs) can be fabricated by spin-coating films of the polymer blends from solution without subsequent processing or heat treatment. Indium-tin-oxide (ITO) and aluminum (Al) are used as the hole-injection and electron-injection electrodes, respectively. Blue light emission is observed at about 8 V and have a peak emission wavelength at 448 nm at room temperature. The EL efficiency is about 0.82%, which is greater than.that of pure PPP by approximately one order of magnitude.

Preparation and second-harmonic generation of grain-oriented transparent BaO-B2O3 glass ceramics

Qinyuan Zhang, Yonghua Zhao, Zhonghong Jiang

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Optically transparent 50BaO (DOT) 50B₂O₃(in mol%) glass-ceramics, in which the surface crystallized layer was composed of an a-axis oriented beta-BaB₂O₄(BBO) fine grains, have been successfully prepared by the conventional melting-quenching technique and subsequent controlled heat treatment. X-ray diffraction (XRD) and scanning electron microscope (SEM) shows that glass crystallization occurred on samples surface in a range of about 2 micrometer in thickness. Only beta-BaB₂O₄ crystalline phase was detected in samples sintered at temperature below 930 degrees Celsius. The spherical crystalline particles-size is about 0.2 micrometer in average diameter. Second harmonic generation (SHG) signals from the transparent surface crystallized samples were observed using a Q-switched pulsed Nd:YAG laser at a wavelength of 1.064 micrometer.

X-ray diffraction analysis of self-organized InAs quantum dots

Yan Zhuang, Y.T. Wang, W.Q. Ma, et al.

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A series sample of GaAs/InAs/GaAs was studied by double crystal x-ray diffraction and the investigation based on the x-ray dynamical theory was used to analyze the x-ray diffraction results. As the thickness of InAs layer exceeded 1.7 monolayer, 3-dimensional InAs islands occurred. Pendellosung fringes were shift. A multilayer structure model is proposed to describe the strain status in the InAs islands and the sample and a good agreement is obtained between the experimental and theoretical curves.

Blue second-harmonic generation and temporal stability of polyureasulfone films prepared by polymerization during poling

Cheng Ye, Pingrong Yu, George K.L. Wong

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Poled polyureasulfone thin films having excellent transparency from near UV to visible region have been prepared by carrying out additional polymerization of 1,4- phenylene diisocyanate and 4,4'-diaminodiphenyl sulfone simultaneously with poling. The polymerization process is monitored by in-situ second harmonic generation. Under optimal conditions, d₃₃ as large as 8.5 pm/V at a second harmonic wavelength of 532 nm has been obtained. SHG intensity decreased to about 84% of its initial value after having been kept at 100 degrees Celsius for over 1000 hours. Wavelength dispersion measurement of SHG coefficients indicates that d₃₃ of prepared poled films increases by about a factor of three at a second harmonic wavelength of 400 nm.

High contrast ratio asymmetric Fabry-Perot optical modulators based on GaAs/AlGaAs multiple quantum wells

Zhibiao Chen, Hongda Chen, Wen Gao, et al.

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A three-layer model and transmission matrix method are developed to analyze the modulation characteristics of GaAs/GaAlAs multiple quantum well asymmetric Fabry-Perot optical modulators. Two conditions of zero reflectivity for getting high contrast ratio are demonstrated and used to design normally-on and normally-off modulators. Low reflectivity of about 5% and high contrast ratio of about 10 are achieved.

Effects of stoichiometry in semi-insulating GaAs on optoelectronic devices

NuoFu Chen, Hongjia He, Yutian Wang, et al.

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The influences of point defects, dislocations, and precipitates on the lattice parameter of undoped semi- insulating GaAs single crystals were analyzed. It was shown that dislocations in such crystals serve as effective gettering sites for As interstitials due to the deformation energy of dislocations. The lattice parameters of these dislocated regions remain relatively constant due to the counterbalance between lattice compression and dilation around the dislocation. Regions away from dislocations show a linear dependence of lattice parameter with As interstitial concentration. Measurements of the lattice parameter in these latter regions by the nondestructive measurement of stoichiometry technique can be used to determine As interstitial concentrations. The nonuniformity in semi-insulating GaAs results in the variation in the threshold voltages of corresponding devices.

Realization of parallel subtraction using LCLV in optical neural network

Bin Wang, Jianwen Yang, Xu Liu, et al.

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Basing on the method of wavelength and beam direction encoding for implementing a bipolar optical neural network, a liquid crystal light value (LCLV) is used to encode the positive and negative light spots by adding relevant light biases so as to obtain the normal and inverse states, respectively. Then, the two modulated light spots in the same group are moved together by using a grating or a lenslet array. The overlapped light spot whose power is just the expected subtractive results of positive and negative weighted summation can be obtained. Taking advantage of said method, parallel operation between positive and negative light spots can be fulfilled. Due to the high discrimination and quick responsibility of LCLV, system operation speed can be greatly enhanced in optical neural network on a large scale. The feasibility is demonstrated by the preliminary experiment.

Photocurrent spectrum of p-i-n Zn1-xCdxSe/ZnSe multiple quantum well heterostructures

Jiu Yao Tang, Yoichi Kawakami, Shizuo Fujita, et al.

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Photocurrent spectrum (PC) is reported both at room temperature and at 77 K on p-i-n Zn_1-xCd_xSe/ZnSe multiple quantum well heterostructures (x approximately equals 0.12) grown by molecular beam epitaxy. Almost all the exciton transitions, allowed and forbidden, associated with the two lowest electron and three highest hole subbands are clearly observed. With the increase of well width from 22 angstrom to 54 angstrom, an evolution of excitonic structure in PC spectra is demonstrated. Theoretical calculations show a quite good agreement with the measurement results, and from the comparison between theory and experiment, an exiton binding energy for heavy hole of 28 meV, and for light hole of 20 meV are obtained for this type of quantum wells.

Zn1-xCdxSe/ZnSe multiple quantum well photomodulators

Jiuyao Tang, Yoichi Kawakami, Shizuo Fujita, et al.

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ZnCdSe/ZnSe multiple quantum well (MQW) transmission and reflection photomodulators operating at room temperature were fabricated employing quantum-confined Stark effect on the exciton absorption. Samples were grown on p-type GaAs substrates by MBE with an i-Zn_0.87Cd_0.13Se/ZnSe MQW heterostructure sandwiched by a ZnSe p-n junction. The transmission modulator was constructed with a Zn_0.87Cd_0.13Se/ZnSe MQW glued onto a piece of ITO film-covered glass with silver paste and epoxy. To avoid absorption in GaAs substrates, a window with a diameter of about 2 mm was opened using a selective etch. For the reflective use an Al mirror was deposited on the glass back surface, the device then operates in reflection with the light to be modulated making a double pass through the active quantum well region, thereby increasing the modulation amplitude. Measurement results are given in this paper for transmission, reflection, differential transmission, differential absorption, and differential reflection as a function of the incident photon wavelength and the applied field.

Organic inclusion complex novel materials for optical second-harmonic generation in ultraviolet region

Fanqing Meng, Mengkai Lu

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Herein is presented a new class of materials for second harmonic generation (SHG) -- organic inclusion complex, in which 'SHG-active units' (guest) are incorporated into chiral handle polycondensed anions (host) through short hydrogen bonds. The former can provide nonlinear optical response. The latter is expected to produce noncentrosymmetric structural 'molecular framework' and improve fundamental properties of materials such as thermal stability, mechanical strength and fabrication behavior, et al. Several new SHG active inclusion complexes were synthesized. In particular, optically fine bulk crystals of urea-(d)tartaric acid (UDT) and urea-(dl)tartaric acid (UDLT) have been obtained. They have good powder SHG intensity and short cutoff wavelengths.

Large-scale flourine-doped textured transparent conducting SnO2 films deposited by APCVD

Honglei Ma, Deheng Zhang, Youpeng Chen, et al.

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Large scale (30 by 30 cm) transparent conducting F-doped textured SnO₂ films have been prepared by atmosphere pressure chemical vapor deposition (APCVD). Uniformly polycrystalline SnO₂:F films having a variable preferred orientation have been obtained with resistivity as low as 5 multiplied by 10^-4 (Omega) cm, with carrier concentrations between 3.5 multiplied by 10²⁰ and 7 multiplied by 10²⁰ cm^-3 and Hall mobilities from 15.7 to 20.1 cm² V/s. The average transmittance (including diffusion transmittance) is higher than 90% in the wavelength range of the visible spectrum and the maximum infrared reflectance reaches 92% for a film 655 nm thick. Substrate temperature, fluorine flow rate are main parameters affecting sheet resistance and transmittance of the resulting films. Oxygen flow rate also influences the film quality in some extent.

Unusual resonance effect of flourescence emitting from sinters of rare-earth-oxide Er2O3 and some inorganic oxides

Zhengwei Liu, Jian Liu, Zhezhao Zeng

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We report for the first time that energy upconversion occurs when the same material was excited by monochrome light of different wavelength. The TTQLL (Three Times Quantum Liquid Law) Fermi Resonance Fluorescence Law advanced by the author in reference 1 is further proved, that is, the peak value of the excited fluorescence posses the following relationships with the wavelength of the excitation light: (lambda) ₀/4, (lambda) ₀/3, (lambda) ₀/2, 2(lambda) ₀/3, 3(lambda) ₀/4, (lambda) ₀, 5(lambda) ₀/4, 4(lambda) ₀/3, 3(lambda) ₀/2, 2(lambda) ₀, 3(lambda) ₀. We also further discussed the radiation mechanism of this fluorescence and provided a theory model.

New nonlinear crystal CsLiB6O10

Xiurong Zhang, Shunxin Zhang, Yao Ci

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CsLiB₆O₁₀ crystal have been discovered to be a new nonlinear crystal for UV application and to have many advantages. So, there is currently much interest in research work for scientists. In the paper, we report on growth and UV NLO properties of the CLBO crystal and compared with other borate crystals.

Xe+2Cl- formed in HCl+Xe-doped crystalline CO

Xingzhi Sheng, Fengmei M. Liu, Xiaoyong Zhao, et al.

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THe emission spectrum of Xe₂⁺Cl^- in HCl plus Xe doped crystalline CO, excited by 308 nm laser, are firstly observed. The cooperative charge transfer absorptions: HCl plus Xe plus 2 hv yields [Xe⁺(HCL)^-] is demonstrated, and the four-body, two-photon cooperative absorption cross section at 308 nm is 5 multiplied by 10^-42 cm⁴s.

Research on solid electrochromic mirror

Yong Ji, Yu-bin Miao, Pen-fei Zhou, et al.

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The electrochromic mirror has prospective applications in rear mirror of automobiles. Starting with the technique of electrochromic mirror, this paper presents the research results of such a mirror. When evaporation a five-layer thin film stack i.e. glass/ITO/NiO(Lithiumed)/Ta₂O₅/WO₃/Al on a transparent glass substrate, we can obtain an electrochromic mirror. We find that the coating technique will play a key role on the function of the device. The thickness of some layers is critical for the mirror, these layers are NiO, Ta₂O₅ and WO₃. The actually prepared mirror with such structure has a reflectance variation from 70% to 15%. The switching time is about 15 seconds and 7 seconds from bleaching to coloration and from bleaching to coloration respectively. The effects of film structure and composition to the properties of the mirror are measured and discussed by x-ray diffraction, x-photo spectrum and voltammetry. The electrochromic mirror meets the needs for practical application.

Optical model of electrochromic layers

Yong Ji, Yu-liang Wu, Yu-bin Miao, et al.

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As a light-intensity-controlling window, electrochromic layer has large potential applications. Thus it gains more and more attention. The properties of such electrochromic layers as WO₃, NiO_x, TiO₂, V₂O₅, Ta₂O₅ have been studied in this paper. The influences of the evaporation factors, such as substrate temperature, vacuum, oxygen pressure and annealing, and their coloration mechanism, are discussed in detail. In this paper, we present the optical model of these layers, i.e. complex refractive index, N((lambda) ) equals n((lambda) )- ik((lambda) ), and the variations of N((lambda) ) with above conditions. We also studied the changes of N((lambda) ) when we apply positive and negative voltage to the layers. We find that the refractive index n((lambda) ) will become smaller and the extinction coefficient k((lambda) ) will become larger when electrochromic layer is colorized. And the curve of n((lambda) ) and k((lambda) ) will shift to longer wavelength. The longer wavelength absorption is due to impurity, defect, and lattice polarization.

Phase-matching conditions for four-wave mixing in principal planes of biaxial crystals

Xue-Lin Yang, Shengwu Xie

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For general parametric collinear four wave mixing (FWM) or direct third harmonic generation (THG) processes involving fields at four different frequencies, the determination of phase matching (PM) directions becomes considerably difficult. But the situation may be greatly simplified when the incident waves propagate in one of the principal planes. In this case, we present here the criteria for determining whether PM can be satisfied for these processes. The explicit equations, even analytic expressions in some processes for obtaining the corresponding PM directions are presented. Data of PM directions for direct THG in several typical biaxial crystals are given.

Time-dependent ferroelectric coercive field after domain inversion in LiNbO3

Haifeng Wang, Yongyuan Zhu, Shining Zhu, et al.

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It was found that the ferroelectric coercive field of LiNbO₃, both in forward and reverse direction, vary with time after domain inversion. The existence of an internal field decaying as e^-t/(tau ) is proposed, and the related coefficients are fitted.

Optical limiting in two-dimensional nonlinear hetero-superlattice-junction structure

Xiangfei Chen, Ya-Lin Lu, Yan-qing Lu, et al.

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Optical limiting is an essential concept for nonlinear optics and its applications. Recently, the nonlinear response in a two-dimensional (2D) superlattice (a periodic structure with its refractive index modulated in two dimensions) was studied for its potential applications in new optical devices. The available results are only related to the transition between a low transmission state and a high transmission state in the allowed bands. Up to date, optical limiting is not explored in 2D case with one incident wave. In this paper, a novel structure, which is composed of two dissimilar superlattices, is proposed for the optical limiting. The novel structure is named hetero- superlattice-junction structure in this paper. In terms of real-space-matching concept, optical limiting is demonstrated in a 2D nonlinear hetero-superlattice-junction structure, while this phenomena is proved unavailable in a 2D nonlinear superlattice.

Growth of a new self-frequency-doubling medium: optical superlattice Nd:MgO:LiNbO3 and its laser and nonlinear optical properties

Yan-qing Lu, Ya-Lin Lu, Cheng-cheng Xue, et al.

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A new multifunctional active medium: optical superlattice Nd:MgO:LiNbO₃, i.e., LiNbO₃ crystal with periodic ferroelectric domain structures, was grown in our laboratory. The absorption and fluorescence spectra of a sample with the modulation period of 7.5 micrometer were carefully measured and show some differences from the results of common Nd:MgO:LiNbO₃ with monodomain structure. Third-order quasi-phase-matched second harmonic generation was also demonstrated to characterize the nonlinear optical properties of the sample. These results indicate that the optical superlattice LiNbO₃ has great potentials for self-frequency-doubling operation using the maximum nonlinear coefficient d₃₃ of LiNbO₃ and high gain pi polarization at the same time. Pumped by a pulsed dye laser, self-frequency-doubling green light was observed in a cavity with great loss.

Violet and blue light SHG in optical superlattice LiNbO3

Ya-Lin Lu, Yan-qing Lu, Cheng-cheng Xue, et al.

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Optical superlattice LiNbO₃ crystals with modulation periods were grown by Czochralski method. The generation of femtosecond pulses from violet to blue has been demonstrated in optical superlattice LiNbO₃ crystals using third- order quasi-phase-matching. The output power of 9.0 mW at 390 nm, 11.5 mW at 402 nm, and 10.4 mW at 421 nm has been obtained. The dependence of the output power and the acceptance bandwidth on crystal length has been measured and theoretically discussed.

Photorefractive sensitivity and lattice constant of ion-exchanged KTiOPO4 optical waveguides

Yushan Li, Shaojie Ma, Yukiko Kondo, et al.

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We report the fabricated method of Rb/Ba ion-exchanged (KTiOPO₄) KTP planar waveguides and the measuring result of photorefractive sensitivity and lattice constant change in the waveguides, and then report the ideal mol% ratio of Rb to Ba. The experimental results show that the photorefractive sensitivity is 1.2 - 2.3 multiplied by 10^-10 cm²/J, which is independent of Ba ion content and annealed procedure, and the change of lattice constant, which decrease with increase the Ba ion content, is 0.42 - 0.25%.

Digital multiplication using an AO convolver

Shiya He, Qida Zhao, Kuanxin Yu, et al.

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Because optical calculation has advantages of high speed computation, parallel operation and high capacity, it attracts considerable attention and rapidly develops recently. This paper presents an acousto-optic (AO) convolver by which the digital multiplication is performed.

Time-share acousto-electro-optic spectrum analyzer

Kuanxin Yu, Shiya He, Qida Zhao

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The acoustoelectro-optic (AEO) effect is analyzed. A time- share AEO spectrum analyzer is proposed.

Growth and laser characteristics of Nd:Ce:Cr:YAG crystal

Youxi Gui, Yongguo Wang, Xun Yang, et al.

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In this paper the growth and laser properties of Nd, Ce and Cr ions-co-doped yttrium aluminum garnet (Nd:Ce:Cr:YAG) crystals were reported. Nd:Ce:Cr:YAG single crystals were grown in DJL-40D model crystal growth furnace with medium frequency induction heating by Czochralski technique from iridium crucible. The influence of the doping concentration of Nd, Ce and Cr ions on the optical quality and the pulse laser performance of the crystal and the technology conditions for growing high quality crystal were also investigated. The dimension of Nd:Ce:Cr:YAG crystal boules grown is up to (Phi) 40 multiplied by 150 mm. The interference fringe of the laser rods with the dimension (Phi) 5 multiplied by 80 mm is less than 0.5/25 mm and the extinction ratio is more than 26 dB. The pulse laser properties of Nd:Ce:Cr:YAG and ND:YAG laser rods were tested comparatively. The typical pulse laser characteristics of Nd:Ce:Cr:YAG crystal are relatively lower, threshold, higher laser efficiency, and relatively higher output power, better thermal stability and smaller nature divergence angle at Q- switching operation. At the same time, the UV radiation of pump flashlamp will not lead to the reduction of laser output.

Measurements of electronic nonlinearity of poly-4BCMU waveguide with surface plasma excitation

Jun Zhou, Yingli Chen, Zhuangqi Cao, et al.

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In this paper, our study is concerned with the metal-clad poly-4 BCMU film waveguide. The Kretschmann configuration of ATR techniques has been used to excite surface plasma wave, and the third nonlinear susceptibility (chi) ⁽³) of the poly-4BCMU film is measured. This method is extremely sensitive for the change of refractive index of the waveguide, it can be served as a useful probe means for monolayer organic films. Another advantage of the method is that the signs of the nonlinear refract index n₂^NL of the organic film can be obtained in the experiment.

Two-dimensional multichannel acousto-optic modulator and acousto-optic matrix-vector multiplication

Qida Zhao, Shiya He, Kuanxin Yu, et al.

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A set of coupled wave equations for two-dimensional multichannel acousto-optic interaction is set up, and its solutions are derived. The characteristics of the two- dimensional multichannel acousto-optic interaction are analyzed theoretically. A new type of two-dimensional multichannel Bragg acousto-optic modulators are made, and its characteristics are measured. The theoretical analyses are supported by experimental results. The matrix-vector multiplication operation can be performed by our two dimensional acousto-optic multichannel modulator.

Novel optical filter for improvement in contrast of images

Guangyin Zhang, Jingjun Xu, Qian Sun, et al.

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In this paper, we examined the saturation absorption nonlinearity of Azo doped polymers, based on which we successfully realize a novel optical filter for improvement in contrast of images.

Designing effective organic nonlinear (NLO) optical materials

Yang Cao, Bo Zhao, Weiliang Zhu, et al.

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In order to know how we can design effective NLO materials, we have studied several series of aromatic hydrocarbons used as NLO materials and found criteria as follows: (1) When the conjugated system is small then the nitro-group is an effective acceptor, and some of this kind of compound has a very high SHG response while fairly big conjugated compounds whose acceptor is nitro-group often reveal weak or no nonlinearity. (2) The compounds whose acceptor (-NO₂) and donor (-NH₂, -NHR or -NR₂) are para-substituted on both ends of the conjugated chains always have very weak or SHG (second harmonic generation). (3) The substituted groups such as -CH₃, -OCH₃, -X(-Cl, -Br, -1) and biphenyl (C₆H₅C₆H₄-) are the best donors which are beneficial to SHG response and transparency. (4) The relatively big conjugated compounds often reveal fairly good second-order nonlinearity when greater than C equals O acts as their acceptor. We studied these laws theoretically and experimentally so as to give some useful guides to the research of the SHG materials.

Preparation and photovoltaic properties of Nd2O3 nanometer powders

Xiangting Dong, Guangyan Hong, Dejun Wang, et al.

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Nd₂O₃ nanometer powders were prepared by precipitation method. XRD analysis showed that Nd₂O₃ nanometer powders were cubic in structure at 600 degrees Celsius; and hexagonal at 850-1000 degrees Celsius, space group was D₃²-P 321. TEM analysis indicated that Nd₂O₃ particles were spherical in shape and increased in size with the increase of calcination temperature. The synthesized Nd₂O₃ nanometer powders were studied by surface photovoltaic spectroscopy (SPS) and field-modulated surface photovoltaic spectroscopy (FMSPS). The observed spectral features can be explained in terms of charge transfer and interband transition.

Dispersion and nonlinear decaying properties of Corona-poled NPP side-chain polymer waveguides

Fubin Gao, Feng Jin, Rubing Xing, et al.

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The preparation and corona-poling process of NPP [N-(4- nitrophenyl)-(s)-prolinol] side-chain polymer waveguides was developed, and its optimum process parameters were given in this paper. The dispersion and nonlinear decaying properties of the poled polymer waveguides were studied for the design and fabrication of waveguide frequency doubling devices.

Stable second-order nonlinear optical waveguide with interpenetrating polymer network

Rubing Xing, Feng Jin, Fubin Gao, et al.

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The electro-optic (EO ) properties of stable second-order nonlinear optical waveguide with interpenetrating polymer network (TPN) was reported. The two-side leaky mode method for measuring EO coefficients of IPN films was presented. The relationships between EO coefficients and waveguide synchronous angle changes caused by applied voltage were derived. The measured values of EO coefficients of IPN are reported. Keywords : electro-optic coefficients ; interpenetratingpolymer network ; waveguide

Spectral properties of Tm3+:LiNbO3 crystal

Xiaoming Wang, Yongfeng Ruan, Taiju Tsuboi, et al.

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In this paper, the absorption and fluorescence spectra of Tm³⁺:LiNbO₃ crystals at room temperature were reported for the first time. The energy levels and experimental absorption oscillator strengths were obtained from the absorption spectrum. According to Judd-Ofelt theory, the intensity parameters (Omega) _(lambda ) ((Omega) ₂ equals 3.30 multiplied by 10^-20 cm², (Omega) ₄ equals 1.37 multiplied by 10^-20 cm², (Omega) ₆ equals 0.84 multiplied by 10^-20 cm²) were worked out by a least-square-fitting procedure. With these values, electric dipole oscillator strength, radiative transition probability, radiative lifetime, branching ratio and integrated emission cross-section were calculated. The potential use of Tm³⁺:LiNbO₃ crystal as a laser material was also discussed.

Fabrication of periodically inverted domain structures in LiTaO3 using ion inducing

Wanghe Cao, Lina Li

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The experiment indicated that Si ion has an action of suppressing protons widthwise diffusion and increasing the depth during the selective proton exchange process of LiTaO₃. It also suggested that Si ion may induce the domain inversion.

Elimination of lateral core and reduction of central core for Nd:YAG crystal

Tengyu Jiang, Xuezhen Xu, Xiji Chen, et al.

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The process for Czochralski growth of convex interface Nd:YAG laser crystal with [111] seed was studied. The forming mechanisms of central core and lateral core through growth of facets were discussed. The relations between the shape of solid/liquid interface and temperature gradient in the melt and facets' growth were described. The technical methods of elimination of lateral core and reduction of central core were achieved. The good results of growth of lateral core-free and smaller central core Nd:YAG crystals were got through designing apparatus and temperature field to maintain steady growth interface pattern.

Spin-splitting of the energy band for strained superlattices with three materials

Yuan Tian, Yuheng Peng, Wei-You Chen, et al.

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In this paper, the valence band spin-splitting for the strained superlattices composed of Al_yGa_1-yAs, Al_xGa_1-xAs and GaAs was studied. By varying the material compositions or the layer thickness, we observed that the subbands corresponding to the spin-up and spin-down split when the superlattices unit-cell is asymmetrical about the cell center. The spin-splitting is defined as the splitting for both spin-up and spin-down in a spin degenerate subband. Moreover, the splitting mainly occurs at the region where the heavy hole and light hole interact on each other strongly.

Measuring two-dimensional electrostatic field by using electro-optic crystal

Changsheng Li, Xiangqun Cui

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A novel method of measuring the two-dimensional electrostatic field is presented. Based on the dual transverse Pockels effect in some crystals, the electro- optic phase retardation and the azimuth angle of the principal axis in this type of crystal are separately controlled by the applied electric field magnitude and its direction. Therefore, the magnitude and direction of the unknown electric field can be determined by measuring the phase retardation and the azimuth angle. Within the range of 50 kV/m, the experiment on measuring the two-dimensional electrostatic field by using a z-propagating LiNbO₃ crystal shows that the nonlinearity errors are less than 4.5% for the field magnitude measurement, and less than 2.3% for its direction. This method will probably be applied to the spot measurement on the two-dimensional electrostatic field.

Growth and optical properties of Bi2Ti2O7 single-crystal thin films on Si(100) by atmospheric pressure metalorganic chemical vapor deposition

Hong Wang, Z. H. Wang, M. Wang, et al.

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In this paper we report the epitaxial growth of Bi₂Ti₂O₇ thin films on Si(100) by atmospheric pressure metalorganic chemical vapor deposition technique (APMOCVD). The source materials used were triphenyl bismuth [Bi(C₆H₅)₃] and titanium isopropoxied. The substrate temperature was as low as 500 degrees Celsius. The as-grown Bi₂Ti₂O₇ thin films were high quality single- crystal film with (111) orientation. The transmittance of Bi₂Ti₂O₇ film is between 80% - 90% in the wavelength range 380 - 800 nm, and the absorption edge is at 310 nm. The dielectric constant ((epsilon) ) and loss tangent (tan(delta) ) were found to be 120 and 0.01, respectively, at room temperature. The resistivity of Bi₂Ti₂O₇ film higher than 1 multiplied by 10¹² (Omega) .cm under the applied voltage from minus 5 V to plus 5 V.

Waveguide Raman scattering of C60 solid film

Guowei Yang, Fangcheng Yuan, Zhongqiu Yu

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In this paper, we studied waveguide Raman scattering of C₆₀ solid film on rough glass substrate. C₆₀ solid films were deposited on smooth and rough glass substrates by subliming C₆₀ powders under the conditions of 10^-5 Torr pressure, 400 degrees Celsius sublimed temperature, and 200 degrees Celsius substrate temperature. The results were that the Raman spectrum of C₆₀ solid films on smooth glass substrates did not show strong Raman lines, and the Raman spectrum of C₆₀ solid films on rough glass substrates showed two strong Raman lines at 1469 cm^-1 and 1572 cm^-1, it was the effect of enhanced waveguide Raman scattering of C₆₀ solid films on rough glass surface. Based on optical waveguide theory, the mechanism of the effect was suggested, the potential applications of the effect in analysis of structure and property of C₆₀ solid film had been put forward.

Crystal growth, laser, and spectroscopic properties of Nd:Sr5(VO4)3F

Xianlin Meng, Qing Ye, Li Zhu, et al.

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The new laser host Nd:Sr₅(VO₄)₃F crystal was grown by Czochralski method for the first time in China. Through the systematic studies on its fluorescence spectra, radiative decay time and absorption spectra, some new conclusions on the laser and spectroscopic characteristics of the crystal were reported.

Research on excimer laser-induced chemical vapor deposition of diamond films

Deming Ren, Xiaoyong Hu, Fengmei M. Liu, et al.

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In our work, the result about the research on excimer-laser- induced chemical vapor deposition (CVD) of diamond films is reported. The XeCl excimer laser was employed as active energy source for photodissociation of carbon source gas. The wavelength of the laser beam is 308 nm with pulse-width of 25 ns, output energy of 180 mJ and power density on the local region up to 300 MW/cm². The gas mixture was consisted of aromatics (C₆ H₆ or C₇ H₈) and H₂. The substrate was p-type silicane. The ratio between aromatics and buffer gas (H₂) is from 1:1 to 1:4. The temperature of the substrate was controlled at 300 degrees Celsius. A swan band of C₂ radical (516 nm) can be observed from the emission spectrum of gas mixture. After two hours deposition, the films were analyzed by Raman spectroscopy. It is shown that there is a wide peak at 1552 cm^-1, which is characteristic spectrum of diamond- like films. The diamond-like films were obtained.

Study of optical character on chalcone film

Ouyang Zan, BingKun Qin, Jingyong Liu

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Chalcone film (CHA) is a new electro-optic (EO) polymer film. It is reported to prepare the film, to measure its refractive index (1.521) and EO efficient gamma₆₃ (about 10^-11 m/v), also to realize phase modulation by fiber interferometer in the paper.

Modified vertical Bridgman technique for GaAs crystal growth

Jiayue Xu, Renying Sun, Shiji Fan, et al.

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In the present work, a modified vertical Bridgman technique for GaAs crystal is developed. The VB configuration in prototype includes a quartz ampoule and a quartz crucible. The quartz ampoule was sealed in order to prevent volatilization of components. Because the decomposition pressure of GaAs ia about 1 atm. at its melting point, the quartz ampoule can keep its shape under 1300 degrees Celsius in air atmosphere during GaAs growth. Seeded 25 mm diameter crystals are grown at the rate of about 0.1 - 0.6 mm/hr under the temperature gradient about 10 degrees Celsius/cm at the solid-liquid interface, and electrical properties of as-grown GaAs crystal are discussed.

Investigation of the ion-implanted PbSe crystal

Jiancheng Zhang, Wenhai Wu

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In order to fabricate the photodiode, P-type of PbSe, was implanted by phosphorus ion(P++)) to form p-n junctions in the materials with incident energy of E_o equals 200 keV and doses of Ds equals 1 multiplied by 10¹⁴, 5 multiplied by 10¹⁴, 5 multiplied by 10¹⁵ ions/cm², respectively. Rp, (Delta) Rp and the depth of the junction were measured and theoretically calculated by means of modification of LSS theory and Bragg principle. The results show that the experimental data of Rp are in agreement with computer simulation, and the electrical parameters of the p-n junctions in PbSe are also discussed. PbSe photodiode was by ionic implantation with performances, ideal factor of diode m equals 2.31, diffusion length L equals 51.4 micrometer, diffusion coefficient D equals 26.52 cm²/s, non-equilibrium minority carrier lifetime (tau) equals 9.96 multiplied by 10^-7s.

Bright blue electroluminescence from Poly(N-vinylcarbazole) doped with two dyes

Baijun Chen, Jingying Hou, Haiyan An, et al.

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Electroluminescent (EL) devices were fabricated using Poly(N-vinylcarbazole) (PVK) doped with two high fluorescence blue dyes, 1,1,4,4-Tetraphenyl-1,3-butadiene (TPB) and 2,5-Bis(5-tert-buty 1-2-benzoxazoly) thiophene (BBOT) as an emitting layer, a layer of tris(8-quinolinolato aluminum (III) (Alq₃) as an electron-transporting layer, and aluminum as the electron-injecting top electrode contact. The cell structure of glass substrate/ITO/doped PVK/Alq₃/Al was employed. In this cell structure, electron and hole are injected from the aluminum electrode and positive polarity, respectively. Then transport into emitting layer and recombinate concomitant electroluminescence from the doped PVK layer. The EL device has a relatively low turn-on voltage of 4 V dc bias, and a luminance of 1200 cd/m² were achieved at a drive voltage of 10 V. The blue emission peaking at about 455 nm and 475 nm.

LiCaAlF6:Cr3+ laser crystal growth by modified Bridgman method

Guangyu Zhang, Wen Liu, Renying Sun, et al.

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Cr:LiCaAlF₆ crystal was grown by modified Bridgman method. The growing process was described in detail. The distribution of Cr along the crystal growth direction was measured and the results showed that the segregation coefficient of Cr is less than 1 under this condition.

Blue upconversion with excitation at 970 nm in Yb0.18-doped Tm0.03LaP5O14/Tm0.1LaP5O14

Zhao Hao, Xiaobo Chen, Guangyin Zhang, et al.

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Much strong blue emission has been observed in pentaphosphate non crystals at room temperature, highly doped with Yb³⁺ and Tm³⁺ when excited into the Yb³⁺ ²F_7/2 state and the excited states of Tm³⁺ at 966 nm by laser diode. Energy transfer and back transfer between the two rare earth ions, participation of phonons, and pair induced quenching were demonstrated to be responsible for the upconversion process.

Multiphoton upconversion process in Er-doped and Er- and Yb-codoped ZBLAN

Xiaobo Chen, Zhao Hao, Guangyin Zhang, et al.

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Blue, even ultraviolet emissions and very strong green emissions have been observed in ZBLAN glasses codoped with Er³⁺ and Yb³⁺. The strong green emissions were demonstrated to be of sequential two-photon process, while the blue emissions be of multi-photon process, due to the strong sensitization of the Yb³⁺. The schemes of luminescence sensitization and quenching of Yb³⁺ to Er³⁺ were proposed.

Spectroscopic properties of Cr3+x:La1-xP5O14 glass

Jin Kai Chen, Wenqin Wang, Jinxin Zhang, et al.

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The basic spectroscopic properties of Cr³⁺:LaP₅O₁₄ glass have been investigated. Weak crystal field (Dq equals 2.12) and strong electron-phonon coupling lead to a broad ⁴A₂ yield ⁴T₂ luminescence in 720 - 1120 nm range. The measured and calculated results also show it has a rather large absorption and emission cross- sections. This kind of glass can be considered as a material for tunable infrared laser.

Optical-limiting effect of polydiacetylenes substituted with heterocyclic group

Peiwang Zhu, Congxuan Yu, Jingyong Liu, et al.

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As a kind of nonlinear optical materials, polydiacetylenes (PDAs) have attracted great attention because of their large third-order susceptibilities, ultrafast responsibilities, and high damage threshold, etc. 5-(2-methylthio-4-methyl)- pyrimidinyl-2,4-pentadiyne-1-ol (PDAA) and its derivatives were synthesized. The optical limiting characteristics of these compounds were demonstrated with nanosecond and picosecond pulses at 532 nm. With linear transmittance as high as 87%, the limiting threshold and limited amplitude of PDATS(PDAA tosylate) were observed to be 200 mJ/cm² and 150 mJ/cm² respectively, which are lower than that of C₆₀ with the same high transmittance for visible light. A five-level model describing reverse saturable absorption (RSA) of PDATS was proposed to explain its optical limiting effect. The excited-state absorption cross section and the excited-state lifetime were estimated to be 4.0 multiplied by 10^-19 cm² and 0.6 microseconds respectively.

Research of the mode coupling equations in nonlinear medium

Liu Huang, Li Wang, Yu Zhao, et al.

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In this paper, a simple form of the steady-state wave equation of a single frequency is derived by using the slow- varying amplitude approximation in the symmetrical nonlinear medium. We calculate and deal with the equation in application of the steady-state mode coupling in nonlinear optics.

Guided-mode method for measuring electro-optic coefficients of poled polymer waveguides

Fubin Gao, Feng Jin, Rubing Xing, et al.

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A guided-mode method is proposed to determine the electro- optic (EO) coefficients of poled polymer waveguides. This method is based on the measurement of the ordinary and extraordinary refractive indices in poled polymer waveguides by using the prism coupling technique. The relationship between EO coefficients and the change of the index ellipsoid of poled polymer waveguides caused by an applied electric field are derived. The EO coefficients of corona- poled DANS(4-dimethylamino-4'nitro-stilbene) side-chain polymer waveguides are measured by using this method.

Studies on 7-hydroxyl-4-methylcumarin as an organic optical nonlinear material

Weiqun Zhou, Yang Cao

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The values of the second-order polarizability of twenty- three derivatives from coumarin were calculated with quantum chemistry program (CNDO/S-CI). 7-hydroxyl-4-methylcumarin was artificially synthesized, and its powder appeared to be particularly effective in second harmonic generation. The single crystal of this compound was grown by solvent evaporation. It is suggested that 7-hydroxyl-4-methylcumarin be an organic high-quality material of double frequency.

Relaxing greatly the limit of thickness of SHG crystal using type I and colinear phase matching

Zhenglie Gong, Guizhi Liu, Zhenping Jiang

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In this paper, the correlation measurement condition and the relative error are derived. The results show that both are dependent upon the factor (1/g₁-1/g₂)1, where g₁ and g₂ are respectively the group velocities of two correlation fundamental pulses, and 1 is the crystal length. It is clear that the limit on thickness of SHG crystal is greatly relaxed as long as type I and colinear matching et fully realized.

Ultrafast photoconductive switch with high voltage and high power

Yanxiong Niu, Yuefeng Wang

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Based on the photoconductive effect of the semiconductor, a photoconductive switch (PS) has been made. At the high dc bias voltage, an electrical pulse with nanosecond rise times, high-power and high-voltage has been generated. In the paper, the physics of the PS under high voltage is discussed.

Analytical model of surface electrode performance for the transverse electro-optic modulator

Yuxu Yeh, QingJi Zeng

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An analytical model for the quadratic electro-optic effect in the PLZT ceramics of the transverse modulator is presented in this paper. From the exact solutions to the electric field and the capacitance of both the single-sided and double-sided surface electrode structures derived by the conformal mapping method, the characters of transverse modulator including the half-wave voltage, switching energy and modulation uniformity for these two electrode structures are calculated for the selection of the electrode geometry. The double-sided electrodes have advantages in half-wave voltage, switching energy and the modulation uniformity over the single-sided electrodes.

Characterization of linear and nonlinear optical properties of urea-tartaric-acid single crystals

Fanqing Meng, Mengkai Lu

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Bulk organic single crystals of urea-(d)tartaric acid and urea-(d)tartaric acid as second harmonic generation (SHG) materials have been prepared from aqueous solution. Their linear properties and nonlinear properties in terms of refractive indices were carried out. The relative effective nonlinear optical coefficients of the two crystals are presented in this paper.

Applications of optical crystals

Yoshiji Suzuki

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The principles of the linear electro-optic effect and the nonlinear optic effect in optical crystals are explained. Devices utilizing these effects, which are a spatial light modulator, an electro-optic probing system and an optical parametric oscillator, are described.

Electro-Optic and Second Harmonic Generation Materials, Devices, and Applications

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