Second-harmonic generation in periodically poled lithium niobate single-crystal fibres

Periodic ferroelectric domain structures were introduced into lithium niobate (LiNbO/sub 3/) single-crystal fibres by the electric field poling method using a configuration of direct electrode contact. The fibres were pumped with a 1064 nm Nd:YAG laser with a CW input power as high as 1 W. The maximum generated second-harmonic signal was 1.6 mW, thus corresponding to an overall conversion efficiency of 0.016%.     

High power output quasi-continuous-wave nanosecond optical parametric generator based on periodically poled lithium niobate

We report on a high power output quasi-continuous-wave nanosecond optical parametric generator （OPG） of congruent periodically poled lithium niobate （PPLN） pumped by a 1 064 nm acousto-optically Q-switched Nd-YVO4 laser （duration. 70 ns,repetition rate：45 kHz,spatial beam quality M2〈 1,3）. The OPG consists of a 38.7 mm long PPLN crystal with a domain period of 28.93 μm. With 5.43 W of average pump power the maximum average output power is 991 mW at 1 517.1 nm signal wave of the PPLN OPG.     

Second-harmonic generation of green light in periodically poled planar lithium niobate waveguide

A periodically poled, planar waveguide in lithium niobate was used to generate 532 nm radiation at room temperature by continuous-wave frequency-doubling with a conversion efficiency of 5% per W cm/sup 2/. Quasi-phase-matching allowed generation of the second harmonic using the d/sub 33/ nonlinear coefficient.<>     

Temperature tunable infrared optical parametric generation based on periodically poled MgO:LiNbO3 crystals

By using a short-pulse field, periodically poled grating (A = 29 μm) was successfully fabricated in a 1.0 mm-thick MgO:LiNbO3 (mole fraction of doped MgO is 5%). A high-repetition-rate optical parametric generation (OPG) based on periodically poled MgO:LiNbO3 (PPMgLN) was pumped by a 1.064 μm acoustooptically Q-switched Nd:YVO4 laser. With 3 W of input pump power, 44 mW of output signal power was obtained at a conversion efficiency of 1.5%. Tunable infrared (IR) output from 1.4538-1.4750 μm was also obtained by tuning the temperature of PPMgLN, which is 45℃-160℃.     

周期性极化掺镁铌酸锂晶体光参量振荡研究

为了实现高转化率3m红外激光光参量振荡输出,采用外加脉冲电场法在厚度为1mm、掺摩尔分数为0.05的镁铌酸锂晶体上成功制备了周期为31.2m的极化光栅,理论计算并模拟了1064nm激光抽运周期极化铌酸锂晶体时,闲频光波长随温度的对应关系,并进行了实验验证。利用1064nm声光调Q Nd:YAG激光器作为抽运源对样品进行了光学参量振荡实验,其中,脉冲激光脉宽为200ns,重复频率是20kHz。在控制温度为80℃、输入抽运光功率为5.567W时,光参量振荡输出波长3m的闲频光功率为1.141W,光光转换效率达到20.1%。结果表明,通过此方法制备的周期性极化铌酸锂晶体光参量振荡,具有较高的光光转换效率。     

基于非周期极化铌酸锂晶体产生任意频率太赫兹辐射

理论上研究并论证了飞秒激光在非周期性极化畴反转的铌酸锂晶体(LN)中由光整流效应产生任意频率、窄带的太赫兹(THz)波辐射的可行性.为实现对THz波谱的整形,文中利用模拟退火(SA)算法设计出铌酸锂晶体的极化畴反转结构的最佳模型,由此可产生任意预置时间波形的THz辐射场.结果表明,SA算法是一种有效的通过设计晶体极化畴...     

周期极化掺镁铌酸锂晶体光参变产生研究

为了获得1.5μm波段可调谐红外光输出,采用短脉冲电场极化法,在1mm厚的掺镁(摩尔分数为0.05)铌酸锂晶体上成功制备了周期为29μm的极化光栅。利用声光调QNd:YVO4固体激光器直接抽运PPMgLN晶体,开展了OPG光学转换研究工作。在输入3W的抽运光时,得到信号光输出功率为44mW,转换效率1.5%。并通过调谐晶体温度(45℃~160℃),获得了调谐范围1.4538μm~1.4750μm的信号光输出。实现了可调谐红外光的输出,验证了晶体周期结构的均匀性。     

基于周期极化铌酸锂晶体的纯态单光子源

纯态单光子源是光量子信息技术的重要资源,它在量子通信、量子计算等新一代信息技术中具有重要的应用价值。本文基于周期极化铌酸锂(periodically poled lithium niobate,PPLN)晶体提出一种小型化、可预知单光子源的制备方案,在满足群速度匹配和准相位匹配条件下,设计一种非简并自发参量下转换过程,产生频率解关联的光子对,进而实现可预知纯态单光子源的制备。从理论上推导出频率解关联的参数条件,详细计算不同条件下光子对产率,研究发现:相同参数条件下,在铌酸锂晶体波导结构中,光子的产生效率比相应体块晶体中提高4—6个数量级。研究结果有助于提高小型化单光子源的纯度和产率,对集成化量子光学芯片进一步发展具有重要推动作用。     

Modeling and experimental observation of parametric fluorescence inperiodically poled lithium niobate waveguides

We present a theoretical and experimental study of parametric generation in a guided wave quasi-phase-matched configuration. A numerical model taking into account inverted domain shape, electrooptic and photorefractive effects, as well as waveguide profiles allows calculation of the observed phase matching curves. The observed parametric fluorescence efficiencies can be explained by assuming a slight reduction of nonlinear coefficient and/or a partial degradation of the nonlinear grating. Optimization of the grating depth profile would permit room temperature parametric oscillation using pump wavelengths and powers attainable with diode lasers     

磁场对周期性极化铌酸锂晶体中产生的窄带太赫兹波的控制研究

本文 利用飞秒激光作用于光折变周期性极化铌酸锂(PPLN)晶体和掺 镁(Mg)的PPLN(PP-Mg:LN)晶体通过光整流效应产生窄带太赫兹(THz) 辐射,通过外加磁场的 办法对THz脉冲串的振幅和寿命进行有效控制。随着外加磁场的增强,在光折变PPLN晶体中 产生的THz 波的振幅和寿命都随之减小;当外加磁场足够强时,光折变PPLN晶体中产生的THz波将完 全被抑制。外 加磁场之所以能够对THz波的振幅和寿命进行有效控制,主要是由于洛伦兹力的作用使光折 变晶体内部产生了空间电荷场。     

Quasi-phase-matched blue light generation in bulk lithium niobate,electrically poled via periodic liquid electrodes

Periodic poling of z-cut lithium niobate is reliably achieved in 0.2 mm thick samples, patterned with photoresist on one face and subjected to pulsed electric fields via liquid electrodes. The acceptance bandwidth for third order second-harmonic generation reveals that the full 3.3 mm length contributes to the conversion     

级联光参量振荡与放大技术研究进展

高性能中红外激光源在科研、民用及军事对抗等领域具有重要的应用价值。级联光参量振荡与放大技术可以显著提高抽运光子利用率,是获取高转换效率、高光束质量和系统高度集成中红外激光的有效方式。介绍了级联光参量振荡与放大技术的基础理论、典型结构以及常用非线性光学晶体,评述了级联光参量振荡与放大技术的研究进展,分析了级联光参量振荡与放大技术在非线性晶体制备、废热管理和镀膜工艺等方面面临的挑战,并对这项技术的发展趋势进行了展望。     

Periodically poled lithium niobate and quasi-phase-matched opticalparametric oscillators

Since their introduction two years ago, quasi-phase-matched (QPM) optical parametric oscillators (OPOs) have moved into the mainstream of OPO research. This has been made possible by continuing improvements and availability of the microstructured nonlinear material periodically poled lithium niobate (PPLN). Demonstrations of PPLN OPOs now span the range of pulse formats and power levels. The most significant area of development is low-peak-power devices where operation with conventional materials is difficult. In this paper, we describe the current state of this research, including OPOs pumped by high-repetition-rate (>30 kHz) Q-switched diode-pumped solid state lasers, and CW singly resonant OPOs with >3-W output power in the 3-4-μm range     

Optical parametric generation covering the sodium D/sub 1/, D/sub 2/ lines from a 532-nm pumped periodically poled lithium niobate (PPLN) crystal with ionic-nonlinearity enhanced parametric gain

We report optical parametric generation from a 532-nm-pumped periodically poled lithium niobate with a wavelength spectrum covering the sodium D/sub 1/, D/sub 2/ wavelengths 589.6 and 589.0 nm. Despite the 8 cm/sup -1/ attenuation at the 5.45 /spl mu/m idler wavelength, the PPLN generates a 9 /spl mu/J/pulse energy near the 589-nm sodium wavelength when pumped by a 130 /spl mu/J/pulse frequency-doubled Nd:YAG Q-switched laser. The observed effective nonlinear coefficient is about 40% higher than its value at the visible and near infrared wavelengths. We believe that this is the first observation of ionic susceptibility enhanced parametric gain in the mid-infrared absorption region of lithium niobate.     

基于PPMgLN的中红外光学参量振荡器研究

对一种基于被动调Q周期极化MgO:LiNbO3(PPMgLN)中红外光学参量振荡器(OPO)的进行了研究.利用Nd:YVO4/Cr4+:YAG被动调Q激光器作为泵浦源,输出得到了1.78 W波长为1064 nm的泵浦光,其脉冲宽度和重复频率分别为10 ns和50 kHz,在倍频晶体PPMgLN作用下,输出得到了波长为3.2 μm功率为360 mW闲频光,光光转换效率达到了20％.周期极化MgO:LiNbO3 (PPMgLN)晶体的极化周期范围为29μm到31.5 μm.通过周期调谐和温度调谐的联合作用,光学参量振荡器(OPO)能够在波长范围3.0～4.0 μm内进行调谐.     

掺铁铌酸锂晶体中光损伤的暗衰减效应

为了研究铌酸锂晶体中的光损伤,着重对掺铁铌酸锂晶体中光损伤的暗衰减效应进行研究,发现在薄样品中光损伤的暗衰减时间远大于在厚样品中的暗衰减时间,利用红外吸收光谱和喇曼光谱对这个现象的潜在机理进行了初步分析,综合几个实验结果发现,晶体厚度对光损伤的暗衰减是一个重要的影响因素.     

Nondestructive characterization of the domain structure of periodically poled lithium niobate crystal based on rigorous coupled-wave analysis

We report rigorous coupled-wave analysis (RCWA) method to non-destructively characterize the domain structure of periodically poled lithium niobate (PPLN) crystal. The strong light diffraction effect is achieved by applying a proper external voltage. We can observe reversed domain pattern and employ the detected diffraction intensity to optimally fit the result of RCWA based on least square method. Compared with conventional scalar diffraction theory, more accurate domain structure parameters with accuracies of 0.05 µm and 0.005 for the period and duty cycle are obtained respectively. It is proved that accurate, real-time and nondestructive characterization can be realized via this method. This work has been supported by the National High Technology Research and Development Program of China (No.2013AA030501). E-mail:wgl@fjirsm.ac.cn      

Plane-wave dynamics of optical parametric oscillation withsimultaneous sum-frequency generation

This paper presents a theoretical analysis of sum-frequency generating optical parametric oscillators where a single nonlinear crystal is used for both parametric generation and sum-frequency generation. In these devices, the parametric and sum-frequency generation processes are both phase matched for the same direction of propagation inside the crystal. Different polarization geometries for which this simultaneous phase-matching condition can potentially be satisfied are identified and categorized, for both birefringent and quasi-phase-matching methods. Plane-wave coupled-mode equations are presented for each of these categories. Solutions of these coupled mode equations and calculation of the single-pass saturated signal gain are outlined. Intracavity signal photon flux density calculations based on these solutions lead to stable steady-state upconversion, multistability, and chaos. The dependence of the photon conversion efficiency on various design parameters are investigated     

10-GHz clock recovery using an optoelectronic phase-locked loop based on three-wave mixing in periodically poled lithium niobate

Clock recovery is a critical function of any digital communications system. To replace the classical electronic phase-locked loops (PLLs) at higher bit rates, several all-optical or optoelectronic clock recovery methods are being studied. This letter presents an optoelectronic PLL where three-wave mixing in a periodically poled lithium niobate (PPLN) device provides the phase comparator. Since PPLN is passive, it generates no amplified spontaneous emission noise; also, the error signal is in the visible (763 nm), therefore easily separated from infrared input signals. Clock recovery is performed on a 10-GHz sinusoidal optical signal. Being based on ultrafast nonlinear effects, this scheme should be able to reach still higher bit rates, on the order of several hundred gigahertz. Also, subclock extraction (e.g., 40-to-10 GHz) should be possible without modifications.