LD泵浦Nd:YVO4晶体KTP腔内倍频红光激光器

报道了激光二极管泵浦Ｎｄ：ＹＶＯ４晶体，Ⅱ临界相位匹配ＫＴＰ晶体腔内倍频红光激光器，通过绎激光晶体热效应的考虑，设计了热不灵敏腔，最大获得了２７３Ｗ６７１ｎｍ红光输出。

Investigation of noncollinear QPM optical parametric amplification based on periodically poled KTP

The properties of noncollinear optical parametric amplification based on quasi-phase matching of periodically poled KTP are investigated theoretically. Our numerical simulation focuses on the gain spectrum of dependence upon noncollinear angle, crystal temperature and crystal angle. At the optimal noncollinear angle and grating period with fixed temperature, there exists a broadest gain bandwidth about 130 nm at signal wavelength of 800 nm. The deviation from optimal noncollinear angle can be compensated by accurately tuning the crystal angle or temperature with a fixed grating period for phase matching. (c) 2004 Elsevier B.V. All rights reserved.

激光二极管侧面抽运调Q倍频Nd:YAG激光器

对高平均功率输出的激光二极管侧面抽运电光调Q倍频 Nd:YAG激光器进行了研究，当采用90个60W的脉冲激光二极管阵列抽运时，在重复频率为10Hz下，实现了最大平均功率为1180mW的1064nm红外激光输出，光-光转换效率为11%。腔外倍频获得600mW的532nm绿光输出，倍频效率达到50%以上。

基于正交频率变换的高功率蓝绿全固态激光器

对多横模全固态激光器使用正交频率变换进行了分析,计算了频率转换效率与激光发散角的关系。使用双KTP晶体正交倍频的方法,对Nd∶YAG激光器输出的含有高阶横模的激光进行倍频实验研究。在1064 nm Nd∶YAG激光基波功率密度为121 MW/cm2时,其谐波转换效率达到75.5%。研究表明,对于光束质量较差的基波激光,采用正交频率变换的方式,适当选择晶体参数,同样可以获得较高效率的二次谐波输出。

532 nm continuous wave mode-locked Nd:GdVO4 laser with SESAM

We obtained continuous wave mode-locked Nd-GdVO4-KTP laser with a SESAM. This is the first report of CW mode-locked Nd GdVO4-KTP laser with a SESAM to our knowledge. 396mw CW mode-locked pulse is achieved at the incident power of 7.653 W, with the repetition about 95 MHz. The pulse duration is assumed to be 5.5 ps, this is the shortest green pulse of 532 nm with SESAM. (c) 2009 by Astro Ltd. Published exclusively by WLLEY-VCH Verlag GmbH & Co. KGaA

Passively mode-locked YVO4/Nd:YVO4 composite crystal green laser with a semiconductor saturable absorber mirror

A diode-pumped passively mode-locked YVO4/Nd YVO4 composite crystal green laser with a semiconductor saturable absorber mirror (SESAM) and a intracavity frequency-doubling KTP crystal was realized. The maximum average output power of 2.06 W at 532 nm with a repetition rate of 100 MHz was obtained at a pump power of 15 W, corresponding to optical slop efficiency 17.2%. The 532 nm mode-locked pulse width was estimated to be approximately 18-ps.

Tunable Fano resonance in photonic crystal slabs

A three dimensional analysis of a special class of anisotropic materials is presented. We introduce an extension of the Scattering Matrix Method (SMM) to investigate the behavior of anisotropic Photonic Crystal Slabs (PhCS) subject to external radiation. We show how the Fano effect can play a fundamental role in the realization of tunable optical devices. Moreover, we show how to utilize electron injection, electric field and temperature as parameters to control the Fano resonance shift in both isotropic and anisotropic materials as Si and Potassium Titanium Oxide Phosphate (KTP). We will see that because Fano modes are sensitive and controllable, a broad range of applications can be considered. (c) 2006 Optical Society of America

晶体的化学键和线性电光效应

晶体的结构和元素组成是与其宏观物理性质相关连的，但是仅仅从这些关系来完成材料的设计工作显然是不充分的。因为结构反映的是晶体中组成元素的位置特征，组成元素则反映了各格位上的个别特征，这两者都是静止参数，不能够反映晶体的整体性质。实际上，在晶体中有一个十分重要的动态因素，即晶体中各组成元素之间的相互作用，也即化学键。这种相互作用可以在一定意义上认为是晶体的组成与结构的综合特征。仔细的研究表明，晶体中的化学键和相关参数正是这种相互作用的重要表征参量。因此，对晶体中的化学键的理解是理解晶体结构与性能关系的一个重要方面，同时，它也必将是晶体性能预测和新型材料设计工作的一个重要出发点和依据。本论文正是从晶体的组成化学键为着眼点，对晶体的结构与其电光性质的关系进行了探索。在薛冬峰和张思远先生得到的二元晶体电光系数的离子-电子部分统一表达式的基础上，应用张思远先生提出的复杂晶体化学键理论，我们得到了一个适用于复杂晶体的普适电光系数表达式。应用我们得到的表达式，我们对一些具有不同结构的复杂晶体（包括一些相对简单的晶体）的线性电光系数进行了计算。这些晶体包括：β-SiC晶体，α-石英晶体，TeO_2晶体，亚硝酸钠（NaNO_2）晶体，钛酸钡（BaTiO_3）和钛酸铅（PbTiO_3）晶体，具有旋光性的氨酸钠（NaClO_3）晶体和Bi_(12)GeO_(20)（BGO）晶体，磺酸酸锂（LiIO_3）晶体，铌酸钾（KNbO_3）晶体，铌酸锂（LiNbO_3）晶体，钽酸锂（LiTaO_3）晶体，磷酸二氢钾（KH_2PO_4）（KDP）晶体，磷酸二氢氨（NH_4H_2PO_4）（ADP）晶体，磷酸钛氧钾（KTiOPO_4）（KTP）晶体，砷酸钛氧铯（CsTiOAsO_4）（CAT）晶体等无机晶体，以及尿素和六次甲基四胺等小分子有机晶体。我们所得到的理论计算结果与相应的实验实测结果基本上吻合得比较好，说明我们的理论方法具有较好的普适性，能够比较合理地揭示复杂晶体中真实的微观物理特征。但是，在计算中也得到了一些与实验结果相差很远的理论结果，说明我们的方法还需进一步完善，以便更好的揭示线性电光效应的物理机制。从我们的计算中更进一步的确证薛冬峰和张思远在计算倍频系数时得到的结果，材料的非线性性质与其线性性质并无直接对应关系，即线性性质优良的原子团并不一定是非线性性质突出的原子团。而且，我们也发现：晶体的非线性性质之间也直接的对应关系，即对某一非线性性质贡献突出的原子团（此外指倍频系数），对另外的非线性性质（此处指线性电光系数）并不一定就有突出贡献。所以，在考虑晶体的非线性性质时，不可以从其某一性质直接外推出另一性质，而是要综合考虑晶体的整体效应（包括线性和非线性的）；有机小分子晶体尿素的电光效应来源于其共轭链O <= C ← N-H中的H-N键和H-O键。而且，由于共轭长度的增加，氧原子与其他原子的距离逐渐增大，具有大电负性的氧原子对共轭链O <= C ← N-H上其他原子C，N，H的影响越来越弱；在六次甲基四氨晶体中，因为计算异极能隙C时，N-C键子式和H-C键子式中，H原子和C原子，N原子和C原子的总的有效价电子数相等，导致异极能隙C为零，从而N-C键和H-C键均显示极强的共价性，而并不显示离子性，进一步导致异极能隙C部分对六次甲基四胺晶体（C_6H_(12)N_4）的线性电光系数的贡献为零。与传统的观点不同，我们在计算中发现，LiNbO_3晶体中对其线性电光效应贡献较大的基团并不是NbO_6八面体，而是LiO_6八面体。在传统的计算中，由于模型的相对简单性和计算的复杂性，多只考虑晶体中阴离子基团的贡献。在我们计算中发现，其中的阳离子基团并不能忽略。相反，在一些晶体如，KTP晶体和CTA等晶体中，往往正是那些阳离子基团在起作用。

Electro-Optical Effect Measurement of Thin-Film Material Using PM Fiber Mach-Zehnder Interferometer

A polarization-maintaining (PM) fiber Mach-Zehnder (MZ) interferometer has been established to measure the EO effect of very thin film materials with optical anisotropy. Unlike a common MZ interferometer,all the components are connected via polarization-maintaining fibers. At the same time, a polarized DFB laser with a maximum power output of 10mW is adopted as the light source to induce a large extinction ratio. Here, we take it to determine the electro-optical coefficients of a very thin superlattice structure with GaAs, KTP, and GaN as comparative samples. The measured EO coefficients show good comparability with the others.

Calculation of second-order nonlinear optical coefficients of KTiOPO4 and KTiOAsO4

The second-order nonlinear optical tensor coefficients of both KTiOPO4 (KTP) and KTiOAsO4 (KTA) are calculated from the chemical bond viewpoint. All constituent chemical bonds of both crystals are considered, and contributions of each type of bond to the total linearity and nonlinearity are determined. Calculated results agree satisfactorily with experimental data in both signs and numerical values. The calculation shows that though TiO6 groups and P(1)O-4 or As(1)O-4 groups have relatively larger linear contributions, they can only produce an advantageous environment for KOx (x = 8, 9) groups and P(2)O-4 or As(2)O-4 groups in nonlinear optical contributions. The origin of nonlinearity of KTP family crystals comes from the KOx (x = 8, 9) and P(2)O-4 groups in their crystal structures. Furthermore, the difference in optical nonlinearities of KTP type crystals is analyzed, based on the detailed calculation of nonlinearities of both KTP and KTA. (C) 1999 Academic Press.