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.     

聚合物非线性光学材料

最近,有机非线性光学材料已引起了人们极大的兴趣。一些可极化有机分子具有很大的分子超极化率,可惜,受晶体对称性的限制仅有少数晶体具有二阶非线性光学效应。极化聚合物可以产生统计非中心对称的环境,使材料的二阶特性显示出来。本文在简单介绍了有机非线性光学和极化的原理后,综述了聚合物二阶非线性光学材料的研究进展。此外,对聚合物的三阶非线性光学效应的研究也作了介绍。     

Synthesis,structural aspects and nonlinear optical properties of novel phthalimide derivatives: theoretical and experimental approach

Novel phthalimides ( 1 , 2 , 3 ) possessing variability of cyclic amines have been synthesized and characterized by analytical and spectroscopic techniques. Phthalimide 1 and 2 crystallized in a triclinic system with space group Pī; however, an orthorhombic system with a chiral space group of P2₁2₁2₁ was observed for 3 possessing piperidine cyclic amine. The hydrogen atoms attached to the central chiral carbon were oriented anti to each other resulting in minimum steric repulsion. The occurrence of C–H···O hydrogen bonds in 1 , 2 , 3 enabled the building of several supramolecular structures. Hyperpolarizability 197.6096 Debye Ų calculated for 1 was found to be higher than the hyperpolarizabilities, 138.0836 and 165.2521 Debye Ų measured for 2 and 3 , respectively. Subsequently, phthalimides ( 1 , 2 , 3 ) were assessed for second harmonic generation (SHG) response, and a negligible response was recorded for 1 and 2 ; however, 3 showed a significant response of 14.2 mV. In addition to acentric structure, helical structural motifs identified in 3 could be responsible for its enhanced SHG response. Copyright © 2014 John Wiley & Sons, Ltd.     

Quadrature Frequency Conversion Scheme Using CsLiB6O10 Crystals for the Efficient Second-Harmonic Generation of High Power Nd:YAG Laser

The ability of CsLiB_6O10 (CLBO) crystals for high power second-harmonic generation (SHG) of a 1064-nm Nd:YAG laser in a quadrature arrangement was experimentally demonstrated. A 532-nm second harmonic output pulse energy of 2.25 J was obtained with 3.21 J of an input 1064-nm fundamental pulse energy at a repetition rate of 10 Hz, corresponding to a power conversion efficiency in excess of 70%.     

Beam characteristic analysis for an unsymmetric single Nd:YAG rod resonator

We theoretically investigate the characteristics of an unsymmetric resonator with single Nd:YAG rod to find the best condition for getting the highly efficient intracavity second harmonics. The beam quality is analyzed with ABCD matrixes including the thermal characteristic of Nd:YAG rod. The analysis is focused on stability, , beam waist and mode-volume of laser beam inside resonator. The results show that the smallest beam waist and a large TEM₀₀ mode-volume can be achieved when a Nd:YAG rod closely contacts one of the laser mirrors. This means that the second harmonics of intracavity type generated under these conditions can be highly efficient.     

单一手性一价铜配位聚合物:晶体结构,荧光,SHG响应及介电性质(英文)

<正>Under hydrothermal conditions,homochiral ligand(4aR,8aR)-2,3-di(thiophen-2-yl)-decahydroquinoxaline (DTDCQ) reacted with CuBr to give 1D helical chain complexes[(DTHHQ)CuBr]_n(1).Single crystal X-ray determination shows that compound 1 crystallize in chiral space groups P2_12_12_1 and the experimental result indicated that 1 has SHG(second harmonic generation) active with approximate responses 0.4 times that of urea,Fluorescent analysis showed it exhibits one intense emission band at 377 nm when the exciting radiation was set at 340 nm. Dielectric constant of compound 1 were measured at different frequencies at room temperature.     

Electrical and nonlinear optical studies of flux grown Mo and Fe doped KTP crystals

The molybdenum (Mo) and ferric (Fe) doped potassium titanyl phosphate (KTP) crystals were grown by high temperature solution growth (HTSG) technique. The concentration of Mo and Fe in grown crystals was measured by EDX analysis. The SHG efficiencies of the Mo and Fe doped KTP crystals were measured and it was found to be 1.77 and 1.38 times respectively higher than that of pure KTP crystal. The frequency dependence of dielectric constant, loss and ac conductivity was studied at room temperature. The phase matching measurements were made using a Q-switched Nd:YAG laser operating at 1064 nm and the measured phase matching angles are 44.2° and 87.88° for Mo and Fe doped KTP crystals respectively.     

Synthesis and nonlinear optical properties of novel Y‐type polyurethane containing tricyanovinylthiazole with enhanced thermal stability of second harmonic generation

A novel Y‐type poly[iminocarbonyloxyethyl‐5‐methyl‐4‐{2‐thiazolylazo‐4‐(1,2,2‐tricyanovinyl)}resorcinoxyethyloxycarbonylimino‐(3,3′‐dimethoxy‐4,4′‐biphenylene)] 4 containing 5‐methyl‐4‐{5‐(1,2,2‐tricyanovinyl)‐2‐thiazolylazo}resorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute part of the polymer backbone, was prepared and characterized. Polyurethane 4 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It showed a thermal stability up to 250 °C in thermogravimetric analysis thermogram and the glass‐transition temperature (T_g) obtained from differential scanning calorimetry thermogram was around 118 °C. The second harmonic generation coefficient (d₃₃) of poled polymer films at 1560 nm fundamental wavelength was around 8.43 × 10^?9 esu. The dipole alignment exhibited a thermal stability even at 12 °C higher than T_g, and there was no SHG decay below 130 °C due to the partial main‐chain character of the polymer structure, which is acceptable for NLO device applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1166–1172, 2010     

Large second-order optical nonlinearities of <Emphasis Type="Italic">s</Emphasis>-triazine derivatives: View from micro molecules to macro crystals

Three s-triazine derivatives have been synthesized and their structures been determined. These are Compound I: 2,4-dimethyl-6-(p-N,N-dimethylaminostyryl)-s-triazine (abbreviated to NMe-1), Compound II: 2,4-dimethyl-6-(p-N,N-diethylaminostyryl)-s-triazine (to NEt-1), and Compound III: 2-methyl-4,6-bis(p-N,N-dimethylaminostyryl)-s-triazine (NMe-2). NMe-1 and NEt-1 molecules belong to the D-π -A type with a one-dimensional charge-transfer character. NMe-1 crystallizes to centrosymmetric space group, while NEt-1 to non-centrosymmetric polar Cc space group with all of the molecular charge-transfer axes taking the same orientation. Under the irradiation of 1064 nm fundamental laser, NEt-1 powder crystals radiate a 2-order harmonic light with an intensity 46.8 times that of urea. The ∧ A typed NMe-2 molecule, which has a two-dimensional charge-transfer character, crystallizes to polar P2₁ space group. Its powder crystals exhibit a 2-order harmonic intensity 46.2 times that of urea. The quantum chemical calculations and tensor analyses have been carried out to reveal the dependence of the macro 2-order nonlinear optical (NLO) efficiency on the micro 2-order NLO coefficients (β) and on the crystalline packing styles.     

芪类分子掺杂极化聚合膜的非线性光学性质

采用实时测量光学二次谐波产生（SHG）和吸收光谱的方法时芪类有机分子DANS（4’－N,N－dimethylamino－nitrostilbene）及一种新合成的经氰基团修饰的有机分子CNDS（α’－cyano－4’－nitro－4－N,N－dimethylaminostilbene）掺杂PMMA[poly（methylmethacrylate）]极化聚合膜的非线性光学性质进行了研究。在电晕极化条件下,由于聚合膜的电导率随温度的变化急剧增加,实验中发现两种掺杂极化聚合膜的最佳电导极化温度均低于它们的玻转温度Tg．在最佳极化条件下,从极化前和极化后的吸收光谱变化可看出CNDS的有序度较DANS的差．但实时SHG表明,CNDS／PMMA极化掺杂聚合膜的二阶非线性系数X（2）较DANS／PMMA极化聚合膜的大．结合极化前和极化后吸收峰强度的变化,我们得到CNDS分了的非线性极化率β约为140×10-30esu.在撤离极化场后,CNDS／PMMA的SHG强度的弛豫也比DANS／PMMA慢,说明CNDS是一种性能较DANS优越的制备二阶光学非线性的掺杂分子．