双轴晶体KTP的色散特性及其倍频PM的表征

讨论双轴晶体KTP单、双极点两类色散方程交换关系及其关系。从KTP色散方程及其参数数据得到折射率、色散曲线、主轴坐标平面上倍频相位匹配（PM）角，并分析各组数据的可靠性及KTP色散特性。分析双轴晶体主平面上倍频PM的表征。     

光参量放大相位匹配角度的计算

给出了单轴晶体ooe,oeo,eoo,eeo,eoe,oee 6种相位匹配方式相位匹配角的解析公式。其中ooe,oeo,eoo 3种可以计算共线及非共线情况,eeo,eoe,oee 3种只能计算共线情况,非共线情况需数值求解,给出了数值求解的方法步骤。研究了双轴晶体折射率在主平面时与单轴晶体折射率的对应关系,利用该对应关系,通过替换折射率的方式求解双轴晶体的相位匹配角度。给出了常见晶体的非共线相位匹配角度图,以供科研人员参考。     

常用双轴晶体连续调谐倍频时的相位匹配特性

本文讨论了常用双轴晶体ＫＴＰ、ＬＢＯ、ＫＮ在基频光波长连续调谐时的倍频相位匹配特性，给出了这三种晶体在不同波长倍频时的最佳相位匹配角的有效倍频极化系数，并纠正了以往计算中的不正确作法。     

放大器非线性失真与最大输出电平的修正

通常，人们在计算放大器非线性失真参数时，往往忽视了一个实际问题，即对计算结果的修正。比如在计算单个放大器组合交调比时，使用公式CM＝CMo＋２（Sob－So）（１）计算多台相同“干放”级联时的干线组合交调比时使用公式CMn＝CMo＋２（Sob－So）－２０lgn（２）（１）和（２）式中：Sob为放大器标称输出电平；So为放大器实际输出电平；CMo为放大器在标称输出电平和标称频道数时的组合交调比；n为干放级联数。又比如在计算单个放大器组合三次差拍比时，使用公式CTB＝CTBo＋２（Sob－So）（３）计算多台干放级联时的干线组合三…     

光纤通信波段KN晶体二次谐波相位匹配角的计算

在光纤通信系统中，超短光脉冲的检测一直是一个重要的问题。二次谐波强度自相关法是被广泛使用的超短光脉冲波形测量的方法。由于光纤通信系统中光功率很低，使得满足晶体的相位匹配变得更加重要。KN作为双轴晶体相位匹配问题比较复杂，本文从双轴晶体主平面上的相位匹配出发，讨论KN的相位匹配问题，得到其在光纤通信波段1．55um处的最佳相位匹配参量。     

连续波激光3／2倍频

意大利科研人员利用非线性晶体实现了连续波（CW）激光的3／2倍频，这项简单的频率转换技术有着广泛的应用，并可能用于光谱学和计量学中。     

双轴晶体有效非线性系数精确表达式

本文从普遍的双折射理论出发,考虑到晶体内基频波D、E分离和倍频波P、D分离,推导出双轴晶体的有效非线性系数的解析表达式,为器件设计提供了必要的参考。     

掺偶氮苯聚合物的光致折射率改变特性

采用表面反射方法研究块状掺偶氮苯聚合物的光致折射率改变特性及其与光强的依赖关系；实验中，使用514nm的圆偏振Ar^ 激光作为抽运光，632．8nm的He-Ne激光(s偏振)作为探测光。通过改变探测光入射角，测量样品在固定光强(0．570W／cm^2)的前向抽运光激励下表面反射率的改变量．研究样品的折射率改变特性．发现样品的光致折射率改变约为0．0035；研究了这种效应对抽运光强度的依赖关系．发现光致折射率改变随抽运光强度增大而增大．当抽运光强为0．800W／cm^2时，折射率改变量可达10^-2量级。     

抑制高峰值功率皮秒激光放大系统Nd:YAG中的自聚焦效应

全固态皮秒放大器的平均输出功率易受到增益晶体中自聚焦效应的影响。通过引入补偿元件砷化镓（GaAs）片可以避免自聚焦效应造成的损伤，关于砷化镓的抑制机理对高峰值功率Nd:YAG晶体皮秒放大器系统的进行理论分析和实验研究。以公式计算得到了GaAs材料的非线性折射率系数，并由数值模拟给出了在抑制自聚焦的最佳效果下GaAs片厚度与Nd:YAG棒长度的关系。在入射皮秒激光束中心波长为1 064 nm、重复频率为1 kHz、峰值功率密度为12 GW/cm2的条件下，进行了不同厚度（200 m和550 m） GaAs片对抑制Nd:YAG棒自聚焦损伤的实验研究。通过优化GaAs片的厚度，该补偿方法在高峰值功率皮秒脉冲条件下，特别是对于Nd:YAG放大器显示出较高的效率。关键词:自聚焦效应；非线性折射率系数；光学损伤； B积分     

高效红外反射偏振器的研究

给出了一个在低折射率透明基底上应用高折射率透明薄膜的高效、Ｐ分量抑制的Ｓ红外反射偏器的实例，对于未被抑制的Ｓ偏振分量的反射率可达Ｒｓ≥９５％，因此可以与金属基底的薄膜反射偏振器相比，并且避免了其升温而要求强迫冷却的麻烦。同时，也研究了薄膜厚度入射角及波长的微小变化（或误差）对于该种偏振器消光率的影响。     

双轴晶体LiB3O5和KTiOPO4的和频特性

本文综述了非线性晶体的和频（ＳＦＭ）特性。对ＬｉＢ３Ｏ５和ＫＴｉＯＰＯ４中的二次谐波产生（ＳＨＧ）和ＳＦＭ进行了数值计算并分析了相位匹配范围,主要的相位匹配参数,最佳相位匹配角θ和Х,有效非线性系数ｄｅｆｆ,走离角α和允许角△θ和△Х。还讨论了在３个主平面内ＳＦＭ的偏振特性。     

Frequency-resolved optical gating measurement of ultrashort pulsespassing through a high numerical aperture objective

We investigate using collinear type II second harmonic generation frequency-resolved optical gating (SHG FROG) to measure the pulse intensity and phase at the focus of high numerical aperture (NA) oil objectives. Because of the strong focusing for such objectives, it is not clear theoretically that such a measurement should work. Such objectives can produce severe distortions of the pulse as a function of radius in the objective. In addition, the standard SHG FROG algorithms are based on the assumption that the fundamental and second harmonic fields are plane waves that can be described by the paraxial approximation, and for high NA objectives, such assumptions are suspect. We show that such measurements work remarkably well. The tight focus, while a theoretical difficulty, eliminates many of the problems traditionally associated with SHG FROG including the difficulty of phase matching and walkoff of different polarizations in the crystal. Specifically, we use collinear type II SHG FROG to measure the intensity and phase at the focus of a Zeiss CP-Achromat 100x, 1.25 NA, infinity-corrected oil objective, and accurately retrieve 20 fs pulses     

椭圆芯光子晶体保偏光纤的优化设计

通过调节椭圆芯光子晶体光纤（PCFs）孔直径和孔间隔，以甲基丙烯酸甲酯（MMA）作为基材，采用本体聚合的方法，研制出2种不同保偏（PM）程度的PCFs预制棒，并采用二次拉伸方法得到2种参数结构的样品，进而针对不同的样品进行PM性能和光学性质测试研究，实验给出椭圆芯PMPCFs最优化的设计参数。     

Second harmonic generation phase-matching locus for 7.5 mol% Nb:KTPcrystals at near-infrared wavelengths

Both the type-II second harmonic generation (SHG) phase-matching locus in the three principal planes of 7.5 mol% Nb:KTiOPO₄ (KTP) crystals for wavelengths less than 1.8 μm and the type-II SHG phase-matching locus for 7.5 mol% Nb:KTP crystals for wavelengths of 970, 980, 1064.2, and 1311.4 nm are calculated on the basis of the Sellmeier equations. When compared with those in KTP crystals, the shapes of these curves are almost the same in the two crystals. These imply that Nb doping does not significantly change the phase-matching properties of KTP crystals, even though it does largely change the phase-matching parameter of KTP crystals. These make Nb:KTP crystals more attractive in direct SHG of semiconductor laser radiation to produce blue coherent light     

保偏光纤侧视成像光强分析及定轴方法研究

保偏光纤偏振轴方位角的确定和调整对改善光纤器件性能有重要意义。为进一步提高定轴精度,国内科研人员在透镜放应侧视(POL)法的基础上提出了五点法、五指法等,其理论定轴精度有所提高。但由于此类方法是建立在特定光强分布的前提下,对成像面调节要求较高,因此其实用性受限。该文以保偏光纤侧视成像为基础,通过对保偏光纤不同成像面的侧视成像光强分布作了大量仿真分析发现,光纤旋转至慢轴与水平方向成0°角附近时,光强分布会发生明显变化,利用这一现象可对0°位置进行识别。因此,该文改变了以往通过寻找某特定光强分布进行定轴的思路,提出了通过对0°位置进行识别的定轴方法,该方法通过简单的图像处理和数据分析即可判断偏振轴的偏转情况,适用的成像面位置范围也相对更宽,可操作性强,实用前景好。     

A technique for improving depolarization measurements beyond 10 GHz: Tilting the polarization planes

Depolarization measurements in linear polarization aiming at determining the effective canting angle of the principal planes and the related anisotropy can be improved, in many important cases, by adopting the simple expedient of tilting the polarization planes with respect to the vertical/horizontal orientations. Optimum tilt angles depend on the system configuration but the choice is not critical in a range spanning from about20degto about30degprovided that the disturbance is small enough (say 50 dB under the copolar level) and/or the anisotropy of the medium is large enough (say 2 dB in the differential attenuation).     

红外非线性晶体Na2Ge2Se5非线性变频模拟计算

对红外非线性光学晶体Na2Ge2Se5的非线性性质进行了研究。计算了在主平面内倍频调谐曲线,0.946μm、1.064μm、1.1319μm泵浦情况下的倍频空间调谐曲线以及和频产生0.589μm激光的匹配曲线,并对计算结果进行了分析比较。所得结果可为Na2Ge2Se5晶体用于特定波长激光器,设计新波段提供理论依据。     

Controlled Vapor Growth and Nonlinear Optical Applications of Large‐Area 3R Phase WS2 and WSe2 Atomic Layers

2D layered 3‐rhombohedral (3R) phase transition metal dichalcogenides (TMDs) have received significantly increased research interest in nonlinear optical applications due to their unique crystal structures and broken inversion symmetry. However, controlled growth of 2D 3R phase TMDs still remains a great challenge. In this work, a direct growth of large‐area WS₂ and WSe₂ atomic layers with controllable crystal phases via a developed temperature selective physical vapor deposition route is reported. Large‐area triangular 3R phase layers are synthesized at a lower deposition temperature. Steady state and time‐resolved photoluminescence spectroscopy and Raman spectroscopy are used to study the unique properties of 3R phase layers due to different layer stacking and interlayer coupling. More importantly, with broken inversion symmetry, 3R phase layers show a quadratically increased second harmonic generation (SHG) intensity with respect to layer numbers. Furthermore, by polarization‐resolved SHG, a uniform polarization preference is observed in bilayer and trilayer 3R phase WS₂, which could be a benefit for practical applications. The results not only contribute to the controlled growth of 2D TMDs layers with different phases but also pave the way to promising nonlinear optical devices.     

ENVISAT ASAR交替极化模式目标检测性能分析

ENVISAT ASAR具有交替极化模式,可以提供3种双极化组合。该文针对3种双极化组合分别推导了几种目标检测器,包括最优极化检测器、白化滤波检测器、张量检测器、单通道检测器等,并使用ROC曲线对它们分别进行了性能比较。结果表明极化白化滤波检测器的性能最接近于理想的最优极化检测器,极大地提高了检测性能。