Phase Matching of SHG in Arbitrary Directions of Biaxial Crystals

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｓｅｖｅｒａｌｂｉａｘｉａｌｃｒｙｓｔａｌｓ ,ｓｕｃｈａｓＫＴＰ ,ＬＢＯ ,ｈａｖｅｓｏｍｅｅｘｃｅｌｌｅｎｔｐｒｏｐｅｒｔｉｅｓ,ｓｕｃｈａｓｌａｒｇｅｎｏｎｌｉｎｅａｒ (ＮＬ )ｃｏｅｆｆｉｃｉｅｎｔｓ,ｗｉｄｅｗａｖｅｌｅｎｇｔｈｒａｎｇｅｓｏｆｔｒａｎｓｍｉｓｓｉｏｎ ,ａｎｄｅａｓｉｌｙｇｒｏｗｉｎｇｌａｒｇｅｓｉｚｅｃｒｙｓｔａｌｗｉｔｈｈｉｇｈｑｕａｌｉｔｙ .Ｔｈｅｂｉａｘｉａｌｃｒｙｓｔａｌｓｈａｖｅｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙｕｓｅｄｉｎｌａｓｅｒｆｒ…     

双轴晶体中非共线相位匹配二次谐波产生现象分析

激光束与其散射光束在晶体中发生非线性和频作用，在满足非共线相位匹配条件时，可观察到二次谐波环的现象。本文以拆射率主轴坐标ｘｏｚ平面为例，推导出了双轴晶体中环参数的近似表达式。并用计算机得出了精确数值解，与实验观察到环的形状完全一致，提出了一种寻找最佳二次谐波产生方向的方法。     

双轴晶体主平面上倍频的相位匹配参量

根据折射率椭球方程及双光轴晶体中光波的传播与偏振特性，分析双轴晶体在主平面内激光倍频相位匹配的特性与方法，导出光波在主平面上传播时倍频的相位失配关系；给出双轴晶体中容许相位匹配倍频的相位匹配角及混频的有效非线性系数deff的表达式。利用可相位匹配的类型、相位匹配角公式和有效非线性系数deff表达式的表，容易对任意一具体晶体在一给定波长求出实际能实现相位匹配的类型或偏振组合，算出相位匹配角，比较不同的相位匹配类型或偏振组合的有效非线性系数，选择最佳的相位匹配类型与方向。从相位失配关系可以计算晶体主平面内倍频的接收角、接收光谱宽度等特性参量。     

双轴晶体中二次谐波产生的最佳相位匹配条件

从二次谐波产生的理论出发，讨论了双轴晶体中二次谐波产生的相位匹配条件，推导了有效非线性光学系数的精确计算公式，以有机非线性光学晶体二苯甲酮为例，给出了对两种基波(1064μm和0808μm)二次谐波产生的相位匹配条件的数值模拟及相应的有效非线性光学系数的精确计算结果，并确定出相应的最佳相位匹配条件. 关键词： 二次谐波产生 最佳相位匹配 有效非线性光学系数 二苯甲酮晶体     

消荧光现象与表面谐波产生

消荧光现象是激光与物质表面非线性相互作用的结果，这是一种普遍现象。在表面谐波产生的研究中，它常常被忽略。大量研究表明：表面谐波产生与消荧光现象，有着密切的内在联系。本文以消荧光观点详细讨论了表面谐波产生的机制，提出了表面谐波产生的消荧光模型。新机制可归纳为：（ａ）多光子受激吸收产生消荧光光斑，（ｂ）激光热效应等促进自发辐射转向准受激辐射，（ｃ）伴随荧光消失，部分产生荧光的激光能量转换为产生表面谐波     

Enhancement of the SHG efficiency in a doubly resonant 2D-photonic crystal microcavity

In this paper we discuss the conditions to obtain the enhancement of second harmonic generation in a two-dimensional circular photonic crystal AlGaAs cavity. The photonic crystal circular cavity offers the possibility of having high-Q resonance modes with respect to those obtained with other types of photonic crystal lattices. The crystallographic cut of the AlGaAs provides a strong nonlinear coupling between a transverse-magnetic (TM) polarized resonant mode at the fundamental wavelength and a transverse-electric (TE) polarized resonant mode at second harmonic wavelength. The double resonance condition leads to a strong improvement of the second harmonic generation process. A preliminary linear analysis has been performed by using the finite-difference time-domain method, which includes the dispersive response of the material, modeled using the well-known one-pole pair Lorentzian function.     

超高真空中C60光聚合效应光学二次谐波的研究

利用１．０６４μｍ基频超短脉冲激光，使用光学二次谐波方法研究了超高真空中蒸镀在多晶银表面上的Ｃ６０薄膜紫外光照射下的光聚合现象，发现聚合以后的Ｃ６０二阶非线性响应增强，同时观察到光聚合的饱和效应，Ｃ６０光聚合二阶非线性的提高可以用电四极了磁偶极子对二次谐波贡献的增强来解释。     

玻璃掺杂量子点的倍频效应产生的理论研究

应用统计理论和量子力学理论对量子点掺杂的倍频效应产生的机制与量子点倍频光的电极化率与量子点的尺寸大小的关系进行了理论研究，结果较好地解释了实验所观察到的规律。     

The Fabrication and SHG Test of QPM Periodically Poled KTiOPO4

The Quasi-phase-matching periodically poled flux-grown KTP by high electrical field method is researched. A 8×5×1mm3, Λ=9.0μm PPKTP wafer is successfully fabricated for the first order QPM SHG. The interactive length of the sample is about 3mm. The SHG scheme of Nd:YAG at 1064nm tested that the output power of cw 532nm green light is 0.2mw at room temperature with fundamental power of 1.2w. The normalized conversion efficiency is about 0.09% (W·cm)-1.     

LiNbO3波导中切伦科夫辐射型的倍频

对条波导中切伦科夫辐射型的倍频作了简要分析，着重分析了产生切伦科夫辐射倍频的，工从实验上实现了条波导中１．０６μｍ红外光到０．５３１ｍ绿光的倍频辐射，转换效率为的０．９％，对应的输入光功率为１０ｍＷ。     

Optical properties and frequency conversion with AgGaGeS4 crystal

The basic optical property and phase-matching of new mixed AgGaGeS_4 crystal are presented. Frequency conversion, in particular the SHG of 30ns pulses of 9μm emission band of transversely excited atmospheric-pressure (TEA) CO_2 laser, is realized in AgGaGeS_4 for the first time. As high as 0.57% peak power and 0.3% external energy efficiencies, and 0.7mJ harmonic pulse energy are obtained for the 9.55μm emission line at pump intensity of 4% level of the damage threshold.     

光学非线性LB膜的时间稳定性与光致漂白效应的关系

用光学二次谐波产生（ＳＨＧ），拉曼散射和紫外－可见吸收光谱等方法研究了偶氮，苯腙及半花菁三种有机染料Ｚ型Ｌａｎｇｍｕｉｒ－Ｂｌｏｄｇｅｔｔ（ＬＢ）多层膜的时间稳定性问题，发现：随着放置时间的推延，其中ＬＢ膜的二次谐波产生信号强度下降，然后逐渐达到稳定；在高压汞灯光照射下，粉末样品中Ｎ＝Ｎ（偶氮），Ｃ＝Ｎ（苯腙），Ｃ＝Ｃ（半花菁）键伸缩振动所对应的拉曼峰强度以及这三类染样在ＬＢ膜样品中对所应的生色团     

双轴晶体光轴角计算的新方法

介绍几何作图计算双轴晶体光轴角的方法、步骤和原理.利用几何作图求得双轴晶体的光轴角,并通过理论推导来证明其正确性.     

周期极化KTiOPO4晶体连续倍频绿光输出

采用外加电场极化方法，在Z切1mm厚的KTiOPO4晶体中实现了周期性极化反转。晶体的极化反转周期为9．0／μm，相互作用长度为3mm。波长为1．064μm的基频光功率为900mW，晶体中心温度为32℃时，获得0．532μm、22μW的倍频绿光输出，二次谐波转换效率为0．0024％。     

Theoretical Study on Intra-Cavity Distributed-Bragg-Reflection Quasi-Phase-Matched Second-Harmonic Lasers

The characteristics of intra-cavity distributed Bragg reflector (DBR) quasi-phase-matched (IDQPM) second-harmonic-generation (SHG) lasers are theoretically studied. In the IDQPM-SHG laser, a QPM device and a DBR for feedback are separately fabricated on the same substrate with the QPM device placed between the DBR and a semiconductor laser. The threshold current of the IDQPM-SHG laser depends on the coupling efficiency between the laser diode and the QPM waveguide and the reflectivity of the DBR. The SH output of the IDQPM-SHG laser is strongly dependent on the generalized SHG conversion efficiency, x. This laser has the potential to attain an SH output over a 30-mW using a currently available 50-mW semiconductor laser for the fundamental light source, when highly efficient QPM device (x=2.2 W⁻¹) is used. Its tolerance for various deviations from the initial design and the problems to develop a commercially available IDQPM-SHG laser are also discussed.     

Optical Anisotropy of Biaxial Magnetic Crystals

The two–dimensional orthogonal representation of electromagnetic waves in crystals is developed. Simple expressions determining the directions of optical axes and dependence of group and phase velocities and polarization vectors on the direction, in the general case, of triclinic crystals of magnetic dielectrics are obtained. A solution of the Maxwell equations in the form of two isonormal harmonic waves is found to be directly related to the exponential, two–dimensional spinor, and three–dimensional tensor representations.     

多波长飞秒激光激发下GaAs纳米线SHG特性研究

本文基于有限元法研究了直立生长于GaAs衬底的GaAs纳米线的光场响应和光场增强性质. 实验使用多个波长的飞秒激光脉冲激发GaAs纳米线, 测得了较高效率的二次谐波信号, 并首次使用宽带超连续飞秒脉冲 (1000–1300 nm) 在纳米线上获取了宽带、无杂散荧光噪声的二次谐波信号. 这种高效的二次谐波产生过程主要归因于纳米结构引起的局域场增强效应. 本文阐明了GaAs纳米线的二次谐波倍频特性, 这些结果对于其在纳米光学中的光器件、 光集成等领域的进一步研究和实际应用具有很好的参考价值. 关键词： GaAs纳米线 二次谐波 飞秒激光     

Thermally Stable and Resonance Enhanced Large Nonlinear Optical Properties In Poled Silica Films Doped with Thiazole Azo Dye

Sol-gel processed poled silica films doped with novel nonlinear organic materials, thiazole azo dye (TA), are prepared in high concentration. Resonance enhanced second-order nonlinear optical coefficient of d₃₃ = 154 pm/V is obtained from TA doped silica film (40 wt%) for the fundamental wavelength of 1064 nm. The value d₃₃ is unvaried for at least 100 h under a high temperature condition (100°C) without any relaxation. Wavelength dependent second-order nonlinearity is also measured.     

掺杂晶体Cd0.35Hg0.65Ga2S4的光学特性

研究了掺杂非线性晶体Cd0.35Hg0.65Ga2S4的线性和非线性光学特性以及相位匹配.在相同的实验条件下，与已知的中红外晶体相比较，测定了该晶体的损伤阈值.实现了CO2激光二次谐波产生实验，与理论预测相一致. 关键词： 掺杂非线性晶体 Cd0.35Hg0.65Ga2S4 二次谐波产生 CO2激光     

掺杂晶体Cd_(0.35)Hg_(0.65)Ga_2S_4的光学特性

研究了掺杂非线性晶体Cd0 35Hg0 6 5Ga2 S4 的线性和非线性光学特性以及相位匹配 .在相同的实验条件下 ,与已知的中红外晶体相比较 ,测定了该晶体的损伤阈值 .实现了CO2 激光二次谐波产生实验 ,与理论预测相一致