周期极化LiNbO3脉冲走离效应分析

建立了包含高阶群速色散的OPCPA 数值模拟程序,并以准相位匹配的周期极化的LiNbO3(PPLN)参量放大器为例,在信号光是中心波长1 053 nm,脉宽100 fs的飞秒脉冲经展宽器展宽800 ps的啁啾脉冲,输入能量约0.6 nJ,泵浦光波长527 nm,脉宽3 ns,初始输入泵浦光强300 MW/cmLiNbO2,PPLN晶体的非共线角1.49°,极化周期9.7 μm的条件下, 对OPCPA过程前级的高阶群速色散引起的走离效应对泵浦光、信号光频谱和脉冲形状的影响等具体特性进行了数值模拟。结果表明：在合适的晶体长度下,高阶群速色散对参量转换效率的影响不大,但它对输出信号光的时间波形和频谱有较大影响,会引起脉冲时间形状畸变和频谱漂移。     

周期极化LiNbO3晶体中电极布置对反转畴扩张的影响

利用外加电场极化的方法,分别研究了三种不同方式布置的极化电极对C向切割LiNbO_{3< /sub>晶体极化反转畴扩张的影响.实验结果表明在相同极化条件下，当极化电极长度方向与六边 形反转畴一对边呈90°和0°角时，极化扩张速度分别为0.089μm/ms和0.011μm/ms.实验结果揭示，为了有效地控制极化占空比，在制备一维准相位匹配LiNbO3晶体时应 避免极化电极与六边形反转畴壁中一对边呈90°的情况. 关键词： 周期极化 极化扩张 准相位匹配}     

二维LiNbO3非线性光子晶体

制备了周期为13.64 μm方形格子二维周期性极化的LiNbO₃，利用二阶准相位匹 配实现了波长为1.064μm二倍频，二次谐波的内部转换效率高达42％. 测量了二次谐波输出功率随晶体温度及入射光入射方向的变化，实验值与模拟计算一致. 制备二阶准相位匹配掩模板，解决了在制备一阶准相位匹配掩模板中遇到周期尺寸太小、数据量大的难题，同时还降低了因周期太小造成的极化难度. 关键词： 二维 准相位匹配 二次谐波     

基于周期极化LiTaO3晶体的高增益简并啁啾脉冲参量放大

根据准相位匹配理论计算了周期极化LiTaO₃(PPLT)晶体中0类准相位匹配过程(e+e→e)的增益曲线.在此基础上，使用数百μJ的低抽运能量获得了～10⁶的增益和～10.3%的转换效率，实现了中心波长位于1064nm的基于简并光学啁啾脉冲参量放大(OPCPA)技术的高增益放大，为产生超短超强激光脉冲提供了新的技术手段.实验结果与理论预期基本符合.     

自相位调制及群速色散对超短脉冲在准周期LiNbO3 Fibonacci超晶格中传输的影响

从LiNbO₃ Fibonacci超晶格的结构特点出发,数值模拟了超短脉冲在LiNbO₃ Fibonacci超晶格内传输过程中,自相位调制及高阶群速色散效应对脉冲形状和频谱的影响．结果表明,超短脉冲在Fibonacci超晶格中传输时,由于自相位调制(SPM)与群速色散(GVD)耦合效应的影响,脉冲形状畸变和频谱展宽均是不对称的,随着晶格长度的增加,脉冲将会发生分裂,以至成为两个独立的子脉冲,同时也会出现脉冲频谱上的分裂. 关键词：     

准相位匹配周期极化钼酸钆制备及倍频效应

根据准相位匹配原理，对钼酸钆晶体用于准相位匹配倍频过程的周期性畴结构进行了设计，当入射基频光为l.064pm时，所需的钼酸钆晶体畴结构周期为5．54μm。利用外电场极化，当外电场为2．5kV／mm时，钼酸钆晶体的畴结构反转时间tc=500～600μs。当外电场脉冲幅值为2．5kV／mm、脉冲延续时间t=0．6～0．8tc时，在钼酸钆晶体中制备得到了周期畴结构。当Nd：YAG纳秒激光器输出准连续功率为7～10mW的l.064μm激光通过具有周期畴结构的样品时，获得了0．532μm的倍频光输出。     

KBe2BO3F2飞秒光参量放大中的群速匹配

提出了KBe₂BO₃F₂ （KBBF）飞秒光参量放大中三波群速完全匹配的方法.对于Ⅰ类相位匹配方式采用非共线结构及倾斜抽运光脉冲波面,对于Ⅱ类相位匹配方式采用共线结构同时倾斜抽运光和信号光脉冲波面,可实现参量带宽最大时三波群速的完全匹配,从而获得更高增益,更窄脉宽的参量光. 关键词： 群速匹配 相位匹配 脉冲波面倾斜 飞秒光参量放大     

基于周期极化LiTaO3晶体的高增益简并啁啾脉冲参量放大

根据准相位匹配理论计算了周期极化LiTaO3(PPLT)体中0类准相位匹配过程(e+e→e)的增益曲线.在此基础上,使用数百μJ的低抽运能量获得了～106的增益和-10.3%的转换效率,实现了中心波长位于1064nm的基于简并光学啁啾脉冲参量放大(OPCPA)技术的高增益放大,为产生超短超强激光脉冲提供了新的技术手段.实验结果与理论预期基本符合.     

非共线准相位匹配周期极化RbTiOAsO_4的增益带宽

研究了非共线准相位匹配过程中,周期极化RbTiOAsO_4晶体同时满足准相位匹配和群速匹配条件的非共线角和相应的极化周期随信号光波长的变化。分析了满足群速匹配条件时,非共线准相位匹配的调谐特性。数值模拟了增益带宽随非共线角、晶体温度和极化周期的变化关系。对比了群速匹配和最大增益带宽情况下,周期极化RbTiOAsO_4晶体增益带宽与晶体温度之间的关系。     

光强对短脉冲在准周期光学超晶格中传输的影响

 在考虑自相位调制和高阶群速色散的情况下，分析了超短脉冲在准周期Fibonacci超晶格中传输时，入射光强对脉冲传输特性的影响。结果表明：入射光强度对脉冲传输特性影响很大，不但使频谱展宽，而且限制超晶格的有效长度，是超短脉冲进行频率转换的主要考虑因素之一。     

Diffusion-bonded stacks of periodically poled lithium niobate

We constructed diffusion-bonded stacks of periodically poled lithium niobate (PPLN). Such crystals combine the advantages of planar processing used to make PPLN wafers with the power-handling capability of large apertures. We demonstrated an optical parametric oscillator that uses a 3-mm-thick diffusion-bonded stack consisting of three 1-mm-thick PPLN crystals.     

High-temperature-recorded index gratings in periodically poled lithium niobate

Holographic index gratings based on a zero-electric-field photorefractive effect are recorded at high temperatures in copper-doped periodically poled lithium niobate crystals. The interplay between the domain structure and the index grating is studied: the fundamental grating with spatial frequency K is strongly suppressed. Pronounced sideband gratings with K(s)=K+sG appear, where G is the domain grating vector and s is an integer number. After development, an additional grating based on the electro-optic effect shows up. In contrast with the previously mentioned gratings, this grating allows anisotropic diffraction.     

Nonlinear directional coupler in periodically poled lithium niobate

Nonlinear wave propagation was investigated experimentally in coupled waveguides by means of the cascaded nonlinearity in quasi-phase-matched second-harmonic generation. With a specially designed wave-vector-mismatch distribution along the propagation axis, cascading was optimized for low fundamental depletion. High-contrast, ultrafast all-optical switching with switching powers of tens of watts was observed.     

Self-optical parametric oscillation in periodically poled neodymium-doped lithium niobate

Self-optical parametric oscillation is demonstrated for the first time to our knowledge in a periodically poled neodymium-doped lithium niobate (Nd:PPLN) crystal. The crystal is pumped by a cw Ti:sapphire laser at 813.5 nm. The Nd(3+) ions absorb the 813.5-nm radiation to generate 1084-nm laser oscillation. The internally Q switched 1084-nm radiation pumps the periodically poled lithium niobate host matrix to generate optical parametric oscillation at 1.55 and 3.6 microm . Up to 24% conversion efficiency from laser to signal is observed.     

Discrete spatial solitons formed in periodically poled lithium niobate by electro-optical effect

We report the numerical observation of discrete spatial solitons in a periodically poled lithium niobate waveguide array by applying an electrical field through electro-optical effect. We show that discrete spatial soliton can be controlled by applied voltage in the periodically poled lithium niobate.     

Electro-optic Solc-type wavelength filter in periodically poled lithium niobate

We demonstrate an electro-optic Solc-type wavelength filter in periodically poled lithium niobate (PPLN). A Solc-type transmission spectrum is observed experimentally in PPLN with four periods from 20.2 to 20.8 microm. Modulation of the transmission power of the filter is realized by application of electric fields along the Y axis of the PPLN. It is observed that the wavelength can also be tuned by temperature.     

Surface-emitted terahertz-wave difference-frequency generation in two-dimensional periodically poled lithium niobate

We report on the demonstration of surface-emitted terahertz- (THz-) wave difference-frequency generation from two-dimensional (2D) periodically poled lithium niobate (PPLN). The two orthogonal periodic structures individually compensate for both the phase mismatch of the launched lasers and the generated THz wave. Tunable 1.5-1.8 THz wave generation with a bandwidth of 10-GHz was obtained by use of two 2D PPLN crystals. We also confirmed that THz waves were simultaneously generated into two opposite directions, which suggests the possibility of higher THz-wave output power.     

Low-threshold spatial solitons in reverse-proton-exchanged periodically poled lithium niobate waveguides

Combining reverse proton exchange and uniform periodic poling in LiNbO3 planar waveguides, we demonstrate low-energy spatial optical solitons by second-harmonic generation at room temperature, with a threshold as low as 23 pJ/microm at 1.5 microm.     

Observation of quadratic spatial solitons in periodically poled lithium niobate

We report what are to our knowledge the first observation and characterization of quadratic spatial solitons in periodically poled lithium niobate (PPLN). Using a Nd:YAG (1064-nm) source, we observed self-trapped solitary-wave propagation over more than six diffraction lengths as a result of the cascaded quadratic nonlinear process. Low-threshold operation (5-kW peak power) was measured for the quasi-phase-matched PPLN structure designed for frequency doubling.