基于单块周期极化铌酸锂晶体级联三倍频的440 nm蓝光固体激光器

阐述了一种基于单块周期极化铌酸锂晶体级联三倍频实现440 nm蓝光输出的实验方案。根据周期极化铌酸锂晶体的Sellmeier方程以及倍频与和频的相位匹配条件,在一块周期极化铌酸锂晶体上设计了两段不同的极化周期,使其在同一工作温度下能分别实现倍频与和频,在先后经过倍频与和频后,实现级联三倍频输出。实验采用Nd: YAG产生的1319 nm光作为基频光,重频400 Hz,脉宽110 ns,横向和纵向光束质量因子分别为1.81和2.65。耦合进周期极化铌酸锂晶体后,出射光中检测到660 nm的红光和440 nm的蓝光。通过调整工作温度和入射基频光功率,得到2.4 mW的最大蓝光输出,此时工作温度55.5 ℃,基频光功率530 mW。实验结果验证了单块晶体实现级联三倍频440 nm蓝光输出的可行性。     

铌酸钾锂晶体的光谱性质和二次谐波产生

铌酸钾锂（ＫＬＮ）晶体是一种能对近红外半导体激光进行倍频获得蓝光输出的非线性光学晶体,是人们感兴趣的一种非线性光学材料［１］。曾用多种生长技术生长了ＫＬＮ晶体,并对其倍频性能作过报道［１,２］。本文报道用电阻加热引上法从高Ｌｉ２Ｏ含量的熔体中生长的Ｋ...     

低电场周期极化化学比掺镁铌酸锂绿光倍频器

对气相平衡扩散输运工艺制备的化学比掺镁铌酸锂晶体进行周期极化,实验中发现化学比掺镁铌酸锂晶体的矫顽场为12kV/mm,只有常用的同成分铌酸锂晶体的矫顽场的1/20,用低电场就可以制备出结构均匀周期为62～64μm的周期性极化结构.在室温下对此周期极化结构进行二次谐波倍频实验,其归一化倍频转换效率为48%/W。     

准位相匹配铌酸锂波导倍频特性分析与优化设计

用标量有限元方法计算了周期性极化的铌酸锂光波导中模折射率和模场分布,并在计算中引入铌酸锂晶体折射率与温度变化的关系,分析了准位相匹配铌酸锂波导倍频效率与极化反转光栅周期、基频光波长、波导器件温度等关系.理论分析与实验结果符合得很好.在此基础上,分析了波导制作参数与倍频效率、光栅周期与晶体温度,以及温度带宽与光栅通光方向长度等关系,进而对铌酸锂波导倍频器件进行优化设计. 关键词： 铌酸锂 光波导 准位相匹配 有限元     

铌酸钾锂晶全及其宽带二次谐波产生

报道了利用引上提拉法生长晨线性光学晶体铌酸钾锂,并且其实现了对准连续可调谐钛宝激光倍频。在波长为８９０－９５２ｎｍ范围内,通过室温下非监界相位匹配,得到４４５－４７６ｎｍ的二次谐波。抽运光强为１４４－２６９ｎＷ,二次谐波强度为０．５８－１．７３ｍＷ,倍频效率可达０．６５％。     

宽带准连续光纤激光在周期极化铌酸锂中倍频特性的研究

双包层光纤激光器和非线性光学材料(如周期性极化的铌酸锂晶体,PPLN)相结合,开辟了实用性非线性光学器件的一个新领域。研究了准相位匹配周期性极化反转铌酸锂晶体对宽带准连续光纤激光倍频的温度特性和频谱特性。在理论上,从准相位匹配相位失配关系出发,推导了晶体温度与抽运源中心波长的关系以及温度响应带宽,并和已报道实验结果进行了比较,二者符合得很好。此外,还推导了倍频周期极化铌酸锂晶体对抽运基频光源的响应谱线带宽。在实验上,采用长度20mm,极化周期6．5μm,厚度0．5mm的周期极化铌酸锂晶体光纤激光器准连续宽带输出进行了倍频,获得了在不同控制温度下的倍频光光谱,并对此进行了详细分析。     

近化学计量比铌酸锂晶体周期极化畴反转特性研究

采用K2O作助熔剂直接拉晶法和气相输运平衡技术制备出了高质量近化学计量比铌酸锂晶体,研究了铌酸锂晶体中的[Li][Nb]比含量对其畴反转结构和极化电场的影响.实验结果表明:随着晶体中[Li][Nb]比的提高,畴极化反转电场呈明显下降趋势,使用近化学计量比铌酸锂晶体,在4.0±0.5kVmm大小极化电场条件下,成功地实现了1.0mm厚度的周期极化畴反转.并用铌酸锂晶体的Li空位缺陷模型对上述实验结果给出了合理的解释. 关键词： 近化学计量比铌酸锂晶体 周期极化 畴反转     

准相位匹配PPLN倍频理论研究与优化设计

对准相位匹配周期性极化铌酸锂(PPLN)倍频进行了理论研究，并对聚焦高斯光束条件下的倍频耦合波方程进行了求解，给出了准相位匹配倍频转换效率公式，分析了晶体长度与聚焦程度的关系，在此基础上对倍频谐振腔进行了优化设计，以期获得最大的倍频转换效率.本结果对准相位匹配倍频器件的设计具有一定的指导意义. 关键词： 倍频 准相位匹配 周期性极化铌酸锂     

掺Ce,Fe系列LiNbO3晶体光折变效应光存储特性

研究了系列Ce：Fe掺杂以及不同后处理态(生长态、还原态和氧化态)铌酸锂晶体的透过率光谱和光折变全息存储特性。实验结果表明单掺Ce铌酸锂晶体具有较好的图像存储质量和较宽的透过率光谱范围,二波耦合增益相对较低;高掺杂铌酸锂样品的透过率光谱范围较窄,光折变二波耦合增益较低。晶体的后处理对铌酸锂样品的光折变特性影响明显,双掺Ce:Fe还原态铌酸锂晶体具有较高的二波耦合增益;氧化态样品具有较大的透过率光谱范围;还原态样品具有较大的光折变二波耦合增益特性。实验结果还表明在同种样品中难于同时获得大的二波耦合增益和图像存储质量。     

掺镁铌酸锂晶体的缺陷结构及其结晶化学分析

根据铌酸锂晶体本征缺陷的Ｌｉ空位模型，提出了掺镁铌酸锂晶体的缺陷结构模型；计算出了掺镁铌酸锂晶体中Ｌｉ_２Ｏ，Ｎｂ_２Ｏ₅的含量、［Ｌｉ］／［Ｎｂ］比以及晶体的密度随掺镁浓度的变化关系．计算结果与文献中报道的实验结果相符合 关键词：     

非化学计量比铌酸钾锂晶体的光谱特征

用顶部籽晶法生长了一批不同组成的铌酸钾锂晶体。利用近红外cw: Ti-sapphire激光研究了三种组成的经过精细抛光的晶体样品的二次谐波性质,结果表明晶体的二次谐波效应与晶体组成密切相关,Li含量越高的样品倍频效率越高。利用红外Raman光谱技术调查了晶体非线性晶格振动特征,分析了晶体中组分离子浓度对晶体红外Raman光谱特征的影响,探讨了组分离子对晶体二次谐波性质影响的原因。结果表明,晶体中位于C格位的Li离子浓度对晶体Raman光谱产生了强烈的影响,低Li含量晶体中[NbO₆]7-八面体所对应的3个Raman特征光谱线没有峰发生分裂;当晶体中Li离子浓度增加时,ν₅所对应的Raman峰有所加宽,ν₂振动模式出现分裂峰,并在100～400 cm-1范围出现小峰数量增多;当Li离子浓度接近铁电相边界时,[NbO₆]7-八面体结构接近解体,ν₅所对应的Raman峰分裂成3个峰,ν₁和ν₂振动模式发生部分分裂,在100～400 cm-1范围小峰更为突出。这些影响的本质在于晶体中Li含量的提高导致晶体中[NbO₆]7-八面体畸变程度加大,与晶体非线性光学性质相一致。     

Miniaturized diode laser module emitting green light at 532 nm with a power of more than 900 mW for next-generation holographic displays

We present a micro-integrated laser module based on an amplified diode laser and second harmonic generation which is a promising candidate for a green light source in next-generation 3D holographic displays. The light emitted by the amplified laser has a wavelength of 1064 nm, reaches a power up to 8.2 W and has a long coherence length of >400 m. For second harmonic generation, we tested two geometries of periodically poled lithium niobate crystals in single pass: a bulk crystal and a planar waveguide crystal. With the planar waveguide crystal, we achieve an output power >900 mW and a coherence length >20 m at a wavelength of 532 nm.     

Second harmonic generation by femtosecond laser pulses in the Laue scheme

Results of the study of second harmonic generation by femtosecond laser pulses in a lithium niobate crystal with a regular domain structure in the Laue scheme are presented. The angular distribution of the intensity and the polarization properties of the second harmonic radiation are studied. The orders of the corresponding phase-matching conditions and the angular width of the second harmonic maxima are calculated theoretically. The theoretical results are compared with experimental data.     

Simultaneous Q-switching and Frequency-doubling by a Single KTP Crystal in a Diode-pumped Nd:YVO4 Laser

The interrelation between the phase matching condition for second harmonic generation (SHG) and the electro-optic Q-switching in KTP was numerically analyzed. A diode-pumped Q-switched Nd: YVO4/KTP green laser was reported, where the KTP crystal was simultaneously used as both an electrooptic Q-switcher and a frequency-doubling crystal in type Ⅱ phase matching.Compared with the conventional frequency-doubling and Q-switching configuration, low loss and high efficiency characteristics were realized by using a single KTP crystal. The Q-switched green laser pulse with a peak power of 762 W and a pulse width of 12 ns was obtained with 1 W pump power.     

Simultaneous Q-switching and Frequency-doubling by a Single KTP Crystal in a Diode-pumped Nd: YVO4 Laser

The interrelation between the phase matching condition for second harmonic generation (SHG) and the electro-optic Q-switching in KTP was numerically analyzed. A diode-pumped Q-switched Nd: YVO4/KTP green laser was reported, where the KTP crystal was simultaneously used as both an electrooptic Q-switcher and a frequency-doubling crystal in type Ⅱ phase matching.Compared with the conventional frequency-doubling and Q-switching configuration, low loss and high efficiency characteristics were realized by using a single KTP crystal. The Q-switched green laser pulse with a peak power of 762 W and a pulse width of 12 ns was obtained with 1 W pump power.     

高效外腔倍频产生426 nm激光的实验研究

利用与铯原子吸收线对应的852 nm半导体激光作为基频光,泵浦基于周期极化磷酸钛氧钾(PPKTP)晶体的环形腔,进行高效外腔谐振倍频并产生426 nm激光.在理论分析小角度环形腔内的热透镜效应基础上,发现晶体中等效热透镜中心位置并非在晶体的几何中心.在理论分析的基础上,实验上通过精密平移台精细调节PPKTP晶体在腔内位置,使得等效热透镜中心位置与谐振腔的腰斑位置重合,进而减小晶体热透镜效应导致的模式失配对倍频效率的影响.在泵浦功率为515 mW时产生了428 mW的426 nm激光输出,对应的倍频转换效率为83.1%.此高效倍频过程为制备与铯原子吸收线相匹配的非经典光场提供有效泵浦光,为推动量子非经典光场的应用以及量子信息科学的发展奠定基础.     

基于中红外DFG光源的甲烷气体光谱检测方法研究

基于中红外光源的气体光谱检测是新的痕量气体监测与分析方法,在大气监测领域具有重要的应用。构建了一套基于中红外DFG光源的甲烷气体光谱检测系统。该系统以1 550 nm和1 060 nm波段可调谐半导体激光器作为基频光源,采用PPLN晶体作为差频非线性变频器件,实现了3.3 μm处的窄线宽可调谐中红外光源输出。实验结果表明,当PPLN晶体工作温度为99.5℃时,闲频光的输出功率为112 μW,差频转换效率达到1.246 mW/W2。晶体的温度接受带宽为4.3℃,泵浦光波长接受带宽为5.3 nm。在此基础上,分别利用直接吸收法和谐波检测法获得了3 028.751 cm-1处的甲烷气体吸收光谱和二次谐波检测信号。     

Investigation on inorganic potassium lithium sulfate single crystal grown by SR method and its characterization for nonlinear optical application

Inorganic crystal lithium potassium sulfate (LKS) was grown by Sangaranarayanan-Ramasamy technique. Structural parameters of the grown LKS crystal were confirmed by single crystal X-ray diffraction analysis. LKS crystal belongs to hexagonal system with non-centrosymmetric space group P6₃. The functional elements presented in the compound were analyzed by ICP-OES test. Thermal property of the sample was evaluated by tracing TGA and DSC plots. UV–Vis spectral studies revealed the lower cut-off wavelength, transparency and band gap (4.9 eV) of LKS crystal. Multi-shot laser damage threshold value of LKS crystal was found to be 4.2 GW/cm². Using Kurtz and Perry powder technique, the second harmonic generation (SHG) efficiency was found. The photoluminescence, dielectric, mechanical and etching studies were also studied to test the LKS crystal for NLO application.     

Nd：Mg：LiNbO3单晶光学特性的初步研究

本文对Nd:Mg:LiNbO_3单晶的透射光谱、光学均匀性、抗光折变特性、倍频与自倍频特性进行了初步研究.报道了染料激光泵浦的Nd:Mg:LiNbO_3自信频激光实验,实现了非临界位相匹配下的自倍频运转,获得了波长为542.2nm的二次谐波输出.     

A Ferroelectric Frequency-Doubling Material-Potassium Lithium Niobate

The potassium lithium niobate crystals have been grown up. The shapes of solid-melt interfaces which maintaining the steady growth of the potassium lithium niobate crystals have been described. The optical transmission spectrum of the crystal has been surveyed. The perfected crystals showed good Second Harmonic Generation properties.