光纤光栅带内色散特性的离散时域分析

采用多层介质的离散传输线模型表型光纤光栅响应特性，并利用数字信号处理方法对光纤光栅的相位特性进行了分析，研究了用于密集波分复用窄带滤波的变迹光纤光栅的带内色散特性，表明对称变迹光纤光栅的幅度响应与相位响应之间满足希尔伯特变换关系，幅度响应越接近理想的矩形，带内色散越大。并采用耦合模理论数值计算了对称变迹的光纤光栅的反射相位响应和带内群时延情况，验证了分析结果。     

Mechanism for Phase Conjugation Reflections of Two Mutually Coherent Beams from Potassium Sodium Strontium Barium Niobate

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掺铜钾钠铌酸锶钡晶体自泵浦相位共轭研究

用掺铜钾钠铌酸锶钡晶体制成猫式(cat)自泵浦相位共轭器,共轭光反射率高达63%.增加掺铜量,晶体在红光波段效应增强.本文研究了掺杂浓度、激光波段与该器件性能的关系.     

应用诱导互泵浦位相共轭镜的实时图像处理

利用自泵浦诱导的互泵浦位相共轭镜，在１６°切掺铜钾钠铌酸锶钡晶体中，分别对信号图像的完整输出和边缘增强输出实现了两幅图像的实时相加和相减处理。位相共轭输出的成像分辨率高达５０ｐｌ／ｍｍ。     

BaTiO3晶体自泵浦相位共轭中的透射效应

从BaTiO_3晶体自泵浦相位共轭透射光束的出射角随泵浦光束入射角的变化,相位共轭透射光束在晶体中的光路,以及相位共轭透射光束的透射率随泵浦光束和晶体c轴夹角的变化等几方面研究了BaTiO_3晶体自泵浦相位共轭中的透射效应,根据实验结果肯定了自泵浦相位共轭中透射现象的存在.     

Two-wave mixing via reflection population gratings

Theoretical analysis of two-wave mixing (TWM) via reflection population grating, aiming to support current experimental investigations of dynamic gratings in Erbium (Er)-doped fibers, is presented. It is shown that for low recording intensities the stationary TWM via reflection saturated absorption gratings is well described in approximation of a spatially uniform grating amplitude. The analysis of the transient TWM is performed both for rectangular and for sinusoidal phase modulation of one of the recording waves and it is shown how the recorded grating amplitude and characteristic recording time can be obtained from the detected signals. It is pointed out that the majority of the existing experimental results on TWM in Er-doped fibers are qualitatively explained within the framework of the developed model.     

Analysis method for apodised grating structures

A modified method of lines (MoL) technique is presented for calculating the reflection characteristies of apodised fibre gratings. To demonstrate the technique, reflection spectra of fibre gratings with triangular and diamond apodisation profiles were calculated showing significant side-lobe suppression. MoL can accurately calculate not only average power but also field and phase distribution across reflected waves. It is shown that the phase of the reflected light is maximally affected at the edge of the grating stopband.     

Study of the Frog-legs Phase Conjugator in BaTiO_3

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Analysis method for apodised grating structures

A modified method of lines (MoL) technique is presented for calculating the reflection characteristics of apodised fibre gratings. To demonstrate the technique, reflection spectra of fibre gratings with triangular and diamond apodisation profiles were calculated showing significant side-lobe suppression. MoL can accurately calculate not only average power but also field and phase distribution across reflected waves. It is shown that the phase of the reflected light is maximally affected at the edge of the grating stop-band.     

基于光纤叠栅的全光纤声光可调谐滤波器的特性分析

本文提出了一种基于光纤叠栅的全光纤声光可调谐滤波器, 与普通光纤布拉格光栅型全光纤声光可调谐滤波器相比, 该滤波器能够对光纤叠栅的两个中心波长进行同步调制. 理论分析了声波频率和声致应变幅度对基于光纤叠栅的全光纤声光可调谐滤波器的传输光谱的影响, 结果表明, 各阶次反射峰分别以两个主反射峰为中心呈对称关系, 且主反射峰与其所调制出的次反射峰之间的波长间隔与声波频率成正比, 而两个主反射峰所调制出的同阶次反射峰之间的波长间隔与声波频率无关; 声致应变幅度主要影响主反射峰及次反射峰的反射率的变化. 实验中, 分别测试声波频率为390 kHz和710 kHz的基于光纤叠栅的全光纤声光可调谐滤波器的传输光谱, 实验结果的变化趋势与仿真分析结果相一致.     

一维金属光栅的光学反射吸收

利用RCWA(rigid coupled-wave analysis)方法研究了一维金属光栅的反射特性,考察了 瑞利反常、表面等离激元驻波共振和几何共振三种共振吸收机理,分析了这三种机理的相互作用,如表面等离激元驻波共振和几何共振可以形成混合模式. 在反射式复合金属光栅中,确认了第四种共振形式,即相位共振. 数值计算表明相位共振对光学吸收的影响有两种形式: 当光栅周期大于一个波长时,相位共振导致尖锐的吸收峰,峰位在几何共振吸收峰一侧;当光栅周期小于一个波长时,相位共振导致混合模式的共振吸收峰发生劈裂. 对一维金属光栅反射特性的研究增加了对金属光栅共振吸收模式及其相互作用的认识. 关键词： 一维金属光栅 瑞利反常 表面等离激元 相位共振     

Modelling of linearly chirped fiber bragg gratings by the method of single expression

To model chirped fiber Bragg gratings (FBGs) for dispersion compensation in optical fibers a novel method of single expression (MSE) is used. The reformulation of Helmholtz’s equation in the MSE to the full set of first-order differential equations leads to dealing with the electric field amplitude, its derivative, power flow density and phase distributions in any aperiodic media. The phase derivative obtained numerically permits to compute the dispersion slope in the time delay of investigated chirped gratings. Reflective and time delay spectra of linearly chirped gratings of different lengths and chirp coefficients are computed. A self-similarity law for the gratings of the same strength but different lengths and chirp coefficients is revealed. The apodization of gratings is applied to reduce sidelobes in gratings’ reflection spectra and eliminate oscillations in the time delay characteristics.     

Modelling of linearly chirped fiber Bragg gratings by the method of single expression

To model chirped fiber Bragg gratings (FBGs) for dispersion compensation in optical fibers a novel method of single expression (MSE) is used. The reformulation of Helmholtz's equation in the MSE to the full set of first-order differential equations leads to dealing with the electric field amplitude, its derivative, power flow density and phase distributions in any aperiodic media. The phase derivative obtained numerically permits to compute the dispersion slope in the time delay of investigated chirped gratings. Reflective and time delay spectra of linearly chirped gratings of different lengths and chirp coefficients are computed. A self-similarity law for the gratings of the same strength but different lengths and chirp coefficients is revealed. The apodization of gratings is applied to reduce sidelobes in gratings' reflection spectra and eliminate oscillations in the time delay characteristics.     

Incoherent all-optical NAND-, NOR-, and XOR-gate using photorefractive fanning effect

An all-optical computing device is proposed to perform incoherent digital operations, including the NAND, NOR, and XOR gates. Instead of using interferometer-based methods, making use of self-generating noise gratings and the erasure of them by another beam in two photorefractive self-pumped phase conjugators (SPPC), the device is able to process mutually incoherent as well as mutually coherent inputs. Changing the orientations of two polarizers and a photorefractive crystal, we are able to perform incoherent parallel NAND, NOR, and XOR operations with this proposed setup. Received: 18 November 1998 / Revised version: 10 February 1999 / Published online: 12 April 1999     

三角形大带宽反射光谱光纤光栅的设计和制备

反射谱具有三角形形状的光纤光栅在光纤传感等领域中具有重要的应用前景。利用遗传算法设计出了产生三角形光谱分布的光纤光栅的耦合系数沿光纤的分布。计算表明,三角形光谱光纤光栅是可以实现的,其反射带宽可以通过光栅的啁啾量进行调节,常周期的三角光栅反射带宽小,变周期的三角光栅反射带宽大,其带宽同其啁啾量大致相等。实验中,采用光束扫描法制备了反射底宽为0．77nm三角形光谱的光纤光栅。     

Sub-milliwatt sub-millisecond recording of population gratings in ytterbium-doped optical fibers at 976 nm

We report effective formation of population gratings in ytterbium-doped fibers by coherent light at 976 nm, i.e. at the wavelength that is typically utilized for optical pumping of these fibers. The dynamic gratings need sub-mW cw laser power to be recorded and have comparable amplitude (absorption) and phase (refractive index) components. Given the spontaneous relaxation time of a Yb³⁺ meta-stable level of ~ 0.8 ms, the grating formation time proved also to be in the sub-ms region with the phase grating component significantly slower than the amplitude one.     

KNSBN晶体猫式互抽动相位共轭光特性

在KNSBN：Ce晶体中，利用二波耦合作用，在单一光束无法获得相位共轭光的条件下，实现了“猫”式互抽运相位共轭光输出，获得较高的共轭光发射率，实验结果表明，晶体的二波耦合作用可以使晶体的自抽运相位共轭光的阈值光强降低。入射光的入射角范围增大，响应时间缩短。     

亚微米光栅型导光板设计

提出了利用亚微米光栅制作导光板的方法,给出亚微米光栅型导光板的初始结构.用严格耦合波理论计算分析了在满足基底全反射条件的45°入射角下红(700 nm)、绿(555 nm)、蓝(465 nm)三色光垂直出射的亚微米光栅(0.651μm、0.516μm、0.433μm)在槽深0.05~0.9μm之间变化时,透射衍射效率在2%~43%之间变化.分析了亚微米光栅的作用,做出性能评价,并研究了特定范围入射角引起的衍射角变化.     

基于光纤光栅谐振腔的掺镱全光纤激光器设计(英文)

采用数值分析方法分析了光纤长度、后腔镜反射率等因素对激光器输出阈值泵浦功率、输出功率的影响,为全光纤激光器的优化设计提供了理论基础.在设计过程中采用光纤光栅作为光纤激光器的反馈与选频腔镜,通过锥度光纤实现了泵浦模块与掺镱双包层光纤之间的低损耗连接以及高效率的泵浦激光功率传输,成功研制了具备稳定窄化线宽激光输出的掺镱全光纤激光器.实验得到了波长峰值在1 082 .50 nm,谱线宽度0 .113 nm,最大输出功率8 .5 W,泵浦阈值功率0 .8 W,斜率效率为70 .8 %的稳定激光输出.