Synthesis, growth and characterization of l-valine cadmium chloride monohydrate—A novel semiorganic nonlinear optical crystal

Single crystals of l-valine cadmium chloride monohydrate (LVCC), a novel semiorganic nonlinear optical material were synthesized and grown from aqueous solution by slow evaporation method at room temperature. The powder X-ray diffraction pattern and FT IR spectrum analysis confirmed the formation of the new crystal. LVCC has good optical transmission in the entire visible region, which is an essential requirement for a nonlinear crystal. The thermal studies reveal that the material has good thermal stability. The LVCC crystal was characterized by energy dispersive X-ray analysis. The optical second harmonic generation conversion efficiency of LVCC was determined using Kurtz powder technique.     

Nonlinear optical rectification of GaAs/Ga1-xAlxAs quantum dots with Hulthén plus Hellmann confining potential

We investigate the nonlinear optical rectification (NOR) of spherical quantum dots (QDs) under Hulthén plus Hellmann confining potential with the external tuning elements. Energy and wavefunction are determined by using the Nikiforov-Uvarov method. Expression for the NOR coefficient is derived by the density matrix theory. The results show that the applied external elements and internal parameters of this system have a strong influence on intraband nonlinear optical properties. It is hopeful that this tuning of the nonlinear optical properties of GaAs/Ga_1-xAl_xAs QDs can make a greater contribution to preparation of new functional optical devices.     

Nonlinear optical rectification of a hydrogenic impurity in a disc-like quantum dot

An investigation of the nonlinear optical rectification of a hydrogenic impurity, which is in a two-dimensional disc-like quantum dot (QD) with parabolic confinement potential, has been performed by using the perturbation method in the effective mass approximation. Both the electric field and the confinement effects on the energy are investigated in detail. The results are presented as a function of the incident photon energy for the different values of the confinement strength and the electric field. It is found that the nonlinear optical properties of hydrogenic impurity states in a disc-like QD are strongly affected by the confinement strength and the electric field.     

Self-localization of excitons and nonlinear optical properties of J-aggregates in a periodically modulated thin film

Nonlinear optical properties of dye J-aggregates embedded in a one-dimensional periodic medium are analyzed theoretically and numerically. The effect of strain-induced exciton self-localization in a chain of monomers on nonlinear optical properties of the system is investigated for weakly and highly ordered J-aggregates. It is found that exciton self-localization in a periodic medium enhances light absorption and effective optical susceptibility. Optical bistability thresholds are examined for weakly and strongly excited dye J-aggregate thin films. It is shown that the threshold intensity of incident electromagnetic field is lower by more than an order of magnitude as compared to that for a homogeneous medium.     

Optical nonlinearity measurement of 4-(N-methyl, N-hydroxyethl)amino, 4'-nitroazobenzene using a transmittance technique with a phase object (T-PO) with top-hat beams at 600-nm wavelength

The transmittance technique with a phase object(T-PO),for measuring optical nonlinear coefficients is proposed with a top-hat beam.The sensitivity of the T-PO with a top-hat beam is a factor of 4 greater than that with a Gaussian beam.The validity of this method is verified by measuring the nonlinearity of a well-characterized liquid,CS 2 at 532-nm wavelength.The ease of use of this method has been proved by measuring a new compound 4-(N-methyl,N-hydroxyethyl)amino,4’-nitroazobenzene(ANAB) at 600-nm wavelength,indicating that this method can be extended to the measurement of optical nonlinearities in a wide-band spectrum.     

Super-Resolution with a Photochromic Mask Layer in an Optical Memory

The possibility of a super-resolution optical memory using a photochromic mask layer was theoretically discussed. An equation which estimates the transmittance change of the mask layer was derived. The numerical simulation based on the equation showed that the reflectance increase of the layer by photo-irradiation is nonlinear when the optical density of the layer is high. The nonlinear response decreased the crosstalk in adjacent recording tracks and improved the MTF (modulation transfer function) characteristics, resulting in a higher recording density.     

Nonlinear lensing mechanisms in a cloud of cold atoms

We present an experimental study of nonlinear lensing of near-resonant light by a cloud of laser-cooled rubidium atoms, specifically aimed at understanding the role of the interaction time between the light and the atomic vapor. We identify four different nonlinear mechanisms, each associated with a different time constant: electronic nonlinearity, Zeeman optical pumping, hyperfine optical pumping and radiation pressure. Our observations can be quite accurately reproduced using a simple rate equation model which allows for a straightforward discussion of the various effects. The results are important for planning more refined experiments on transverse nonlinear optics and self-organization in samples of cold atoms.     

STEADY SOLUTIONS OF THE OPTICAL SOLITON EQUATION WITH A NONLINEAR RESPONSE DELAY TERM

The exact solution of the optical soliton equation with a nonlinear response delay term has been obtained by using the method of separating variables. The new type of optical solitary wave solution, which is quite different from the bright and dark soliton solutions, has been found for a special case.     

Crystal growth and characterization of L-valine cadmium acetate a semiorganic NLO crystals

A new semiorganic nonlinear optical material, L-valine cadmium acetate, was grown successfully from aqueous solution by slow evaporation method. The grown crystals characterized by using Powder X-ray diffraction analysis confirms the structure of the grown title compound. The functional groups have been identified using FTIR spectral data. Transmittance compound was analyzed by using UV-vis spectrum. The thermal behavior of the grown crystal was determined with the aid of thermogravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The dielectric constant was studied as a function of frequency for various temperatures. The grown crystal has positive photoconductivity nature. The fluorescence spectrum of the crystal was recorded and its optical band gap is about 3.4479 eV. Second order nonlinear optical property of the grown crystal has been confirmed by modified Kurtz–Perry powder second harmonic generation (SHG) test.     

Ultrafast nonlinear optical response of squarylium dye J-aggregates spincoated films and an application to T bps demultiplexer

We have fabricated spincoated film of squarylium dye (SQ) J-aggregates exhibiting ultrafast nonlinear optical response at room temperature and shown a new serial-to-parallel demultiplexer for T bps optical signals using SQJ-aggregates film. Optical dynamics measurements reveal that saturable absorption of this SQJ-spincoated film exhibits a decay time of less than 100 fs at pump energy of 80 fJ/μm². With this ultrafast SQJ optical film, multi-output demultiplexing operations for T bps optical signals were demonstrated. A series of 4 pulses with 100 fs duration and 1 ps interval (corresponding to 1 T bps signals) were irradiated onto the SQJ film synchronized with a 100 fs gate pulse at a finite angle. Four demultiplexed signals were clearly observed at different areas on CCD camera.     

Integration of a Proposed All-Optical Analog-to-Digital Converter using Self-Frequency Shifting in Fiber and a Pulse-Shaping Technique

Integration of a proposed all-optical analog-to-digital (A/D) converter is described. To realize a high-speed and highthroughput system, optical A/D conversion has attracted much attention. A/D conversion generally consists of three processes of sampling, quantization and coding. Whereas an optical sampling technique has already been realized, there have been few investigations on the optical quantization and optical coding technique. We previously proposed an alloptical A/D converter which realizes both optical quantization and optical coding. In this paper, we integrate the proposed all-optical A/D converter to improve its performance and stability. We verify the operation of the integrated all-optical A/D converter composed of a short high nonlinear fiber, arrayed waveguide gratings and variable optical attenuators.     

System for measuring optical admittance of a thin film stack

A new method based on the polarization interferometer structure has been applied to measure the optical admittance, the refractive index and thickness of a thin film. The structure is a vibration insensitive optical system. There is one Twyman-Green interferometer part to induce a phase difference and one Fizeau interferometer part to induce the interference in the system. The intensities coming from four different polarizers were measured at the same time to prevent mechanical vibration influence. Using the polarization interferometer, the optical admittance, the refractive index and thickness of a single layer of Ta₂O₅ thin film has been measured. The measurement results were compared with the results obtained by ellipsometer. The results meet reasonable values in both refractive index and thickness.     

基于光子晶体光纤光脉冲压缩的理论研究

从理论上研究了单根光子晶体光纤的光脉冲压缩,利用较短的具有高非线性系数的光子晶体光纤可以实现较高质量的光脉冲压缩。针对单根光子晶体光纤压缩光脉冲的限制,提出了一种基于光子晶体光纤非线性环路镜中交叉相位调制效应的脉冲压缩方法。理论研究表明,这种脉冲压缩方式可以压缩自身功率较低的信号脉冲,相比于单根光子晶体光纤的方法,可以得到更高压缩质量的脉冲,通过合理选择控制光脉冲的参数,可以有效地抑制基座。     

Lower Exciton Number Strong Light Matter Interaction in Plasmonic Tweezers

The plasmonic nanocavity is an excellent platform for the study of light matter interaction within a sub-diffraction volume under ambient conditions.We design a structure of plasmonic tweezers,which can trap molecular Jaggregates and also serve as a plasmonic cavity with which to investigate strong light matter interaction.The optical response of the cavity is calculated via finite-difference time-domain methods,and the optical force is evaluated based on the Maxwell stress tensor method.With the help of the coupled oscillator model and virtual exciton theory,we investigate the strong coupling progress at the lower level of excitons,finding that a Rabi splitting of 230 meV can be obtained in a single exciton system.We further analyze the relationship between optical force and model volume in the coupling system.The proposed method offers a way to locate molecular J-aggregates in plasmonic tweezers for investigating optical force performance and strong light matter interaction.     

多层膜软X光反射镜的研制

本文介绍了镍-碳多层膜软X光反射镜的设计与制造方法,特别是膜厚监控法.用俄歇谱仪分析了一个样品的剖面情况;对一些样品在1.54(?)的衍射特性和在软X光区的反射率进行了测量并与理论计算结果作了比较.     

施加电场的半抛物量子阱中的二阶非线性光学极化率

利用量子力学中的紧致密度矩阵方法,研究了施加电场的半抛物量子阱中的二阶非线性光学极化率(光整流系数),得到了此系统的光整流系数的解析表达式.数值计算的结果表明,随着电场强度的增加,光整流系数几乎线性随之增加,而且在同样的电场强度及抛物束缚势频率作用下,半抛物量子阱模型中的光整流系数比抛物量子阱模型中的值大一个数量级,这是由于我们所选模型本身的非对称性以及电场进一步使这种非对称性增强的缘故.     

Atmospheric Gas Detection with Broadband Sources

We investigate a new experimental method for detecting molecules from the ultraviolet to the near infrared range using ultrashort laser pulses. Two types of sources are used: a white light continuum generated by 200khz Ti: Sapphire regenerative amplifier system, and a near-gaussian femtosecond pulse (100 fs) generated by an optical parametric amplifier and tunable from 0.45 to 2.4 m. Up to now, this technique has only been performed in the visible domain. Both broadband sources allow the detection of the oxygen and the water vapor bands. Moreover, a new extraction method has been implemented, which provides the molecules' concentration by using a nonlinear fit technique.     

Spatial and Temporal Properties of a Nonlinear Optical Feedback System

We experimentally investigate the spatial and temporal properties of a nonlinear optical system composed of an optically addressed spatial light modulator and a two-dimensional optical feedback. The system property is examined using fringes with only one spatial wave vector. The fringes are spontaneously generated using a spatial frequency filter in the optical feedback. We also experimentally investigate the properties of the spatial light modulator in the system using ordinary interference fringes in order to compare with the system property. We demonstrate that the spatial frequency response of the nonlinear optical system is identical to that of the spatial light modulator. We also demonstrate the distinctive temporal behavior of diffraction lights from the fringes generated in the system.     

激发态分子内质子转移有机分子HBT的三阶非线性光学特性

以532nm皮秒脉冲作抽运光,采用单光束Z-扫描技术对具有激发态分子内质子转移效应的有机分子2-(2′-羟基苯基)苯并噻唑(HBT)在其双光子吸收区的非线性光学特性进行了研究.实验结果表明,对532nm波长的光,HBT分子存在明显的双光子吸收.通过拟合开孔Z-扫描实验数据,求解了HBT分子在其双光子吸收区的非线性吸收系数,并探讨了抽运光强度对介质双光子吸收效应的影响.采用高斯分解法,通过拟合闭孔Z-扫描除以开孔Z-扫描数据,理论推导并计算了在介质对抽运光存在非线性吸收的情况下HBT分子的非线性折射率,以及不同入射光强度时HBT分子的三阶非线性极化率实部和虚部的值.计算结果表明,理论分析与实验结果较好地符合,这些结果为进一步研究和开发此类材料的应用提供了理论与实验依据.     

C60醛类衍生物非线性光学特性研究

研究了加合不同取代基团的C60醛类衍生物的光学非线性性质。利用简并四波混频（DFMW）方法获得了C60醛类各衍生物的三阶光学非线性超级化率γ^(3)及相应的三阶光学非线性系数χ^(3)值。同时也研究了它们各自的光限幅特性。结果表明：不同的取代基对C60醛类衍生物三阶光学非线性及光限幅特性的影响不同。