二维正方形光子晶体填充率对晶体带隙的影响

用有限时域差分方法(FDTD)对比研究了下列二维光子晶体的带隙:第1组,半径r=0.2μm圆柱,折射率n=4,晶格常数a=0.4μm;第2组,半径为r=0.2μm圆柱,折射率n=4,晶格常数a=0.6μm;第3组,内半径r_1=0.1μm,外半径r_2=0.2μm,折射率n=4,晶格常数a=0.4μm;第4组,内半径r_1=0.1μm,外半径r_2=0.2μm,折射率n=4,晶格常数a=0.6μm,并且对每一组光子晶体进行挖孔操作,然后比较不同填充率对光子晶体材料的带隙的影响,以及同种材料和结构、挖孔对带隙的影响。对于紧密排列的二维光子晶体,挖孔会使带隙向长波方向移动;对于填充率小的光子晶体,或者环形柱二维光子晶体,中间挖孔不影响带隙的范围。     

KTP和 7.5 mol% Nb∶KTP晶体在 Nd∶YAG激光中的倍频和和频(英文)

本文在获得精确的 7.5mol% Nb∶ KTP晶体的 Sellmeier主折射率色散方程的基础上 ,计算 7.5mol% Nb∶ KTP晶体对 1 .0 6 42μm和 1 .3 1 88μm Nd∶ YAG激光的倍频和和频的 型相位匹配曲线 .通过研究 KTP和 7.5mol% Nb∶ KTP晶体的主折射率 ,双折射率和相位匹配 ,可以看出 Nb掺入 KTP晶体后产生的折射率和双折射率的色散和各向异型的变化是引起 KTP晶体相位变化的根本原因 .     

一维光子晶体横磁场模的特性

基于平面波展开法,设计三层一维光子晶体横磁场模结构,改变三层介质厚度和介质折射率的大小,应用MATLAB语言进行仿真计算,在一维光子晶体三层介质厚度值为0.4、0.05μm和0.05μm,折射率为1、3N和12N时形成一维光子晶体带隙宽度最宽为0.2694Hz.研究结论为一维光子晶体器件的设计提供理论依据.     

KTP和7.5mol%Nb:KTP晶体在Nd:YAG激光中的倍频和和频

本文在获得精确的7.5mol%Nb:KTP晶体的Sellmeier主折射率色散方程的基础上,计算7.5mol%Nb:KTP晶体对1.0642μm和1.3188μmNd:YAG激光的倍频和和频的型相位匹配曲线.通过研究KTP和7.5mol%Nb:KTP晶体的主折射率,双折射率和相位匹配,可以看出Nb掺入KTP晶体后产生的折射率和双折射率的色散和各向异型的变化是引起KTP晶体相位变化的根本原因.     

Nd^3＋：YAlO3晶体折射率温度系数的表示式

建立了Nd~(3+):YAlO_3(Nd:YAP)晶体折射率温度系数的表示式,该式得到的结果与测量值间具有较好的一致性。利用这个式子可以计算0.5398μm～1.0795μm波长范围311K～455K温度范围内Nd:YAP晶体的折射率温度系数。     

各向异性光学晶体折射率的精密测定

从晶体光学的基本原理出发,研究了各向异性光学晶体(激光晶体、非线性晶体等)折射率的精密测定方法;在0.36～10.6μm光谱范围内建立了棱镜偏向角法测量装置。     

基于混合导光型光子晶体光纤的波分解复用器研究

设计了一种基于混合导光型光子晶体光纤的波分解复用器,该波分解复用器同时具有折射率导光型光子晶体光纤和带隙导光型光子晶体光纤的特点,可用于稀疏型波分复用系统中.设计的稀疏型波分解复用器由一段三芯光子晶体光纤组成,通过填充不同折射率的材料.形成了混合导光型光子晶体光纤.根据耦合模原理,在临近的波导中,当传播常数相等时,模式之间发生强烈耦合.能量在波导之间交替.由于填充的材料折射率不同,使得光功率在两个小同的波长上发生耦合,构成了两个不同响应波长的光滤波器.通过选择合适的光纤长度,使得在光纤的输出端,不同波长的光从不同的波导输出,实现波分解复用的功能.采用全矢量有限元法分析了光纤传输特性,计算了不同波长光的耦合长度.采用光束传播法仿真发现,长度为4.3 mm的光纤能实现波长为1.31μm和1.55μm光的解复用.     

高掺镁铌酸钾晶体的主折射率及其温度系数的测量

本文报道掺5mol%MgO的铌酸锂(liNbO_3)晶体的主折射率n_o、n_o及其温度系数.用自准直法在0.5398μm、0.6328μm、1.0795μm和1.3414μm波长上,并在20℃～160℃温度范周内,测量了该晶体的主折射率,并获得在这些波长上的折射率温度系数.修正的Sellmeier方程的常数也在20℃～160℃温度内推算出.用此结果计算室温的二次谐波I类临界相位匹配角与实验值符合得很好,又计算二次谐波的非临界相位匹配温度,其结果也与实验值较符合.     

液芯高双折射率光子晶体光纤的特性研究

设计了一种纤芯区域由中心椭圆缺陷孔和其横排的上下两侧椭圆孔组成的高双折射率光子晶体光纤,并在其纤芯中心椭圆缺陷孔中填充高折射率液体物质二硫化碳.利用有限元法分析了该光子晶体光纤的双折射率、功率限制因子、模场分布及色散系数特性.研究结果表明:液芯光纤具有较高的纤芯功率限制因子,在波长0.6~1.6μm范围内实现了宽带大负色散系数,在波长1.55μm处光纤双折射率达到了6.8×10-2,即该结构液芯光子晶体光纤同时实现了宽带大负色散和高双折射率特性.通过结构参量容差性分析得到该光纤具有较好的偏振稳定性.     

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％。     

Effect of xylenol orange on the crystalline perfection,optical, piezoelectric and NLO behavior of unidirectionally grown imidazolium L-Tartrate single crystal

Pure and 0.1 mol% Xylenol orange (XO) doped Imidazolium L-tartrate (IMLT) nonlinear optical (NLO) single crystals were grown using Sankaranarayanan–Ramasamy (SR) method of uniaxial solution crystallization technique. The pure IMLT crystal is 100 mm in length and 15 mm in diameter. The doped IMLT crystal is 25 mm in length and 10 mm in diameter. UV–Vis-NIR spectrum shows that the pure and XO doped IMLT crystals' cut off wavelength is 235 nm. High-resolution X-ray diffraction (HRXRD) measurement and birefringence interferometry confirm that the SR method grown crystal has good crystalline perfection and optical homogeneity. The wavelength dependent refractive index and piezoelectric d₃₃ coefficient were measured. The difference refractive index (Δn) of (100) plane in parallel and perpendicular directions shows a strong dependence on wavelength. The dielectric constant, hardness and SHG conversion efficiency were also increased as a result of XO dye doping in IMLT crystal.     

Determination of the refractive index over a wide wavelength range through time-delay measurements of femtosecond pulses

We present a simple method to measure the refractive index dispersion over a broad wavelength range (0.6-1.6 μm). In a first step, the optical group indices are obtained by measuring the time-retardation of tunable 150 fs laser pulses within a sample relative to air. The refractive index dispersion is then calculated using a Sellmeier equation that describes the measured group index dispersion. We show that our experimental data agree with previously published results to within 2 × 10⁻⁴ for a 3 mm thick sample of fused silica and to within 3 × 10⁻³ for the index n₁ of a 2 mm thick crystal of the highly dispersive and anisotropic organic crystal 4-N,N-dimethylamino-4′-N′-methyl stilbazolium tosylate (DAST).     

Negative thermo-optical coefficients and athermal directions in monoclinic KGd(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> and KY(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> laser host crystals in the visible region

The temperature dependence of three principal refractive indices of the biaxial KGd(WO₄)₂ and KY(WO₄)₂ crystals in the temperature range of 288–673 K was measured at wavelengths of 438.5 and 632.8 nm. Their thermo-optical coefficients (TOC) of the first and second orders were determined on the basis of the experimental data obtained. TOC were found to be negative for the n_g and n_p refractive indices of the KY(WO₄)₂ crystal and for the n_g refractive index of the KGd(WO₄)₂ crystal. It was established that in a fairly wide temperature range contributions of the positive and negative TOC to the refractive index of a light wave propagating in these crystals in certain directions compensate each other. Such athermal directions were determined for the index ellipsoid principal planes of these crystals on the basis of experimental data. PACS 78.20.Ci; 78.20.Nv     

Electro-optic tuning of a periodically poled LiNbO3 optical parametric oscillator and mixing its output waves to generate mid-IR tunable from 9.4 to 10.5 μm

We demonstrate electro-optic spectral tuning in a pulsed periodically poled LiNbO₃ (PPLN) optical parametric oscillator (OPO) in ns regime. A 3-cm-long LiNbO₃ crystal is segmented in three equal sections; the outer sections are periodically poled. The center segment is of single domain whose refractive index is changed by electro-optic effect. Applying voltage from 0 to −5000 V, the OPO signal and idler waves are tuned from 1.932 to 1.912 μm and 2.368 to 2.40 μm, respectively. The signal and idler waves obtained are difference-frequency-mixed in a 10 mm long AgGaS₂ crystal to produce mid-IR tunable from ∼10.5 to ∼9.4 μm, which matches the tuning range of a CO₂ laser.     

High efficiency and high energy parametric wavelength conversion using a large aperture periodically poled MgO:LiNbO3

We have demonstrated an efficient high energy 2 μm laser generation with a 36 mm long large aperture 5 mol% MgO-doped periodically poled LiNbO₃ (PPMgLN) nonlinear optical crystal. A high power Q-switched Nd:YAG laser (1.064 μm) was used to pump the quasi-phase matched (QPM) optical parametric oscillator (OPO). A total output energy of 186 mJ with 58% slope efficiency was obtained in two separate beams at 2 μm.     

60°对角视场的折/衍混合透视型头盔显示器

分析了离轴、大视场角透视型头盔显示器光学系统的设计方法,提出了利用衍射光学的独特性质设计了大视场、宽波段、离轴折/衍混合透视型头盔显示器光学系统.该系统具有10 mm的出瞳直径和22 mm的出瞳距离,且满足人因素要求.另外,该系统色差仅14 μm,系统口径小于46 mm,满足双目视觉要求.整个系统适合具有15 mm对角直径SVGA分辩率的彩色液晶显示器（LCD）.     

Refractive index, birefringence, third-order non-linearity and piezoelectric resonance studies of L-lysine monohydrochloride dihydrate single crystals

The principal refractive indices of L-lysine monohydrochloride dihydrate (L-LMHCl) single crystal for different wavelengths were measured by minimum deviation method at room temperature. The experimental values of refractive indices fit well with the theoretical Cauchy's equations. The birefringence and the crossing angle between the optical axes were calculated. The parameters of Sellmeier's single term dispersion equation were determined by least square method. A simple interferometric technique was used to observe the interference patterns along the optic plane and to qualitatively analyze the optical homogeneity of the grown crystal. The nonlinear refractive index (n₂) and nonlinear absorption coefficient (β) were also determined using Z-scan technique. The piezoelectric resonance in dielectric dispersions was observed at room temperature.     

BiB3O6晶体主轴折射率及其温度系数

利用自准直法，在30℃到170℃温度范围内分别测量0.4880 μm、0.6328 μm、1.0640 μm、1.3414 μm等波长下BiB₃O₆(BIBO)晶体的主轴折射率.得到不同温度下的Sellmeier方程及各主轴折射率的温度系数.计算了1.0795 μm下BIBO晶体的的主轴折射率.与实验测量的结果进行比较，两者的差异不大于2×10－4.     

90° phase-matched up-conversion of CO2 laser radiation in AgGa0.86In0.14S2

The CO₂ laser radiation at 10.5910–9.2714 μm was up-converted to the visible in the 90° phase-matched AgGa_0.86In_0.14S₂ crystal by mixing with the output of the 0.3547 μm pumped BBO optical parametric oscillator at 25–120 °C. The new Sellmeier and thermo-optic dispersion formulas that reproduce these experimental results correctly as well as the previously published data [Banerjee et al. in Appl Phys B 87:101, (2007); Opt Commun 227:202 (2007)] for difference-frequency generation at 4.05–6.98 μm and second-harmonic generation at 5.2955 μm are presented.