光子带隙型光子晶体光纤的研究

实验证明,空心的空气-石英光子晶体光纤的纤芯可以局域光,并在理论的基础上,得到光子带隙存在的条件,特定的波带受到限制并沿光纤传导;与每一个波带相对应的光子晶体包层中出现一个完全的二维光子带隙,随着空气填充率的增加,光子带隙的相对大小也会随之变大,而且当减小空气孔尺寸时,光子带隙将被抑制。采用透射谱法在红外波段对带隙型光子晶体光纤进行测量,通过比较光纤的透过谱与光源的光谱,确定是否存在光子带隙。     

压力作用对实芯光子晶体光纤特性影响分析

为了能使光子晶体光纤用于光纤压力传感器等无源器件中,采用弹光理论分析方法对压力作用下光子晶体光纤纤芯和包层中应力、横向结构和折射率分布的变化进行了理论分析和实验模拟,获得了压力作用下对光子晶体光纤中传播光脉冲的相位和模式双折射的影响的数据,采用相干干涉测量技术方法能测量光子晶体光纤中光脉冲相位和模式双折射的波动量值并进一步推算出作用在光子晶体光纤上的外界压力变化量。结果表明,光子晶体光纤可用作光纤压力传感器中的敏感元件。这一结果对光子晶体光纤在光纤压力传感器中的进一步应用是有帮助的。     

带有无序填充气线石英介质的光子晶体光纤

简述了无序光子局域化和光子晶体带隙的关系，介绍了国外多孔光子晶体光纤的研究现状；提出了研制带有无序填充气线石英介质的光子晶体光纤的设想，以及这种新型光纤的优势和它的潜在应用。     

确定光子晶体光纤方位角的散射图案特征法

为了满足加工和制作光子晶体光纤器件时的方位角定位需求,提出基于激光前向散射图案的方位角确定方法。用波长为650nm的激光垂直照射在光子晶体光纤的侧面,拍摄前向散射图案同时实时记录光子晶体光纤端面的显微图像。选取前向散射图案的局部区域强度之和为特征值,通过比较分析得出当求取前向散射图案半幅散射条纹强度值总和时,其特征值变化规律与光子晶体光纤内部轴向结构相对应,可用于光子晶体光纤特殊方位角的确定。在三种不同结构的光子晶体光纤的特殊方位角定位中,该方法的定位精度均小于0.5°,充分证实了该方法的有效性和普适性。提出的光子晶体光纤轴向特殊方位角确定方法简单实用、定位精确,将在光子晶体光纤器件加工中发挥重要的作用。     

高非线性石英基光子晶体光纤产生宽带可调中红外孤子的实验研究

通过研究发现双包层结构能降低石英基光子晶体光纤损耗,并制备一种高非线性双包层结构石英基光子晶体光纤来进行实验研究.使用钛宝石飞秒激光器将实验室自制的石英基光子晶体光纤在反常色散区泵浦,研究不同的泵浦功率和泵浦波长对中红外超短脉冲孤子的影响,并分析了石英基高非线性光子晶体光纤中红外超短脉冲孤子产生的物理机理.结合实验发现在泵浦功率为827 nm,功率从0.1 W增加到0.42 W时,中红外第一个孤子随功率增加从1933 nm移动到2403 nm,可调范围达到470 nm,为石英基光子晶体光纤产生宽带可调超短脉冲源创造了很好的条件.     

1维光子晶体微腔的光子局域特性分析

为了研究光子晶体的光局域特性,采用传输矩阵法计算了1维缺陷光子晶体微腔中缺陷模的局域场强分布,建立了相对局域化长度的概念,它表征光子局域程度的强弱,局域化长度越小,光子局域程度越强,反之亦然.结果表明,缺陷层两侧排列为高折射率介质层的结构局域光的能力比两侧为低折射率介质层的强;考察前一种结构,且满足共振布喇格散射条件或共振米散射条件范围时,相对局域化长度可获得较小值.     

1维光子晶体微腔的光子局域特性分析

为了研究光子晶体的光局域特性,采用传输矩阵法计算了1维缺陷光子晶体微腔中缺陷模的局域场强分布,建立了相对局域化长度的概念,它表征光子局域程度的强弱,局域化长度越小,光子局域程度越强,反之亦然。结果表明,缺陷层两侧排列为高折射率介质层的结构局域光的能力比两侧为低折射率介质层的强;考察前一种结构,且满足共振布喇格散射条件或共振米散射条件范围时,相对局域化长度可获得较小值。     

高非线性光子晶体光纤中的声光相互作用

高非线性光子晶体光纤具有小纤芯、大折射率对比度的特点,其周期性的空气孔结构使得导引声波布里渊散射(GAWBS)激发的声子被束缚在纤芯区域,产生显著的声光相互作用。声子通过调制光纤材料的折射率,从而对光波的相位进行调制。利用Sagnac干涉环将相位调制转化为强度调制,在光子晶体光纤中实现了1550 nm和1060 nm波段GAWBS声子的激发和探测。实验测得在1550 nm和1060 nm波长抽运下声子基模频率均约为1.24 GHz,验证了前向布里渊散射声子频率与抽运光波长无关的理论。     

纳米多晶SiC膜中由强散射形成的谐振腔激射的研究

纳米碳化硅多晶膜构成的无序结构的拉曼受激散射和似激光散射是这种材料的一个新现象。本文讨论了在碳化硅纳米薄膜中出现的拉曼受激散射和随机激光现象，提出拉曼受激散射阈值降低的原因在于纳米晶体的散射截面增大，而随机激光是由于纳米晶体构成的无序结构因光在其中产生局域化所致。此外，本文还报道了荧光辟裂的现象，初步认为是纳米无序结构形成的光子禁带产生的作用。     

太赫兹波段金属光子晶体光纤增强拉曼散射现象的研究

深入探究了金属光子晶体光纤的表面增强拉曼散射现象,建立了时域有限差分法的平板结构的模型,利用观察到的超强透射现象得到了发生拉曼散射的理论依据。金属光子晶体在太赫兹波照射下的表面电磁场增强效果的实验中得到:入射波能量越大,更易激发产生金属光子晶体的表面等离子体共振,可以使金属表面的增强效果得到较大增强;拉曼散射效果在太赫兹波段内十分明显,吸收光谱效果和荧光效应也相对较小,能够显著提高灵敏度和分辨率。     

Measurement of Raman scattering in single-mode optical fiber byoptical time-domain reflectometry

The measurement of the Raman scattering in a single-mode optical fiber using optical time-domain reflectometry (OTDR) is reported. The OTDR technique makes it possible to determine the power level of the pump and Stokes components along the fiber without cutting it back, and to estimate Raman scattering parameters in a reliable manner. The measurement method is described and experimental results are discussed. It is concluded that the power conversion process to higher Stokes components has been clearly displayed without cutting back the fiber     

PMD Distribution Measurement by an OTDR With Polarimetry Considering Depolarization of Backscattered Waves

In previous studies of polarization-mode-dispersion (PMD) distribution measurement by an optical time-domain reflectometer with polarimetry (p-OTDR), scatterers were assumed to be clouds of nonspherical particles in a fiber. However, the pulsewidth dependence of the degree of polarization (DOP) could not be explained by the assumption of nonspherical backscattering alone. In this paper, it is reported that the p-OTDR waveforms were fitted well by modified Mueller matrices under the assumptions of scattering by cloud of spherical particles and a reduction in the DOP due to the interference of the backscattered waves with the phase fluctuation. A PMD distribution measurement is demonstrated based on the p-OTDR Jones matrix eigenvalue method with the assumption of slowly varying PMD along the fiber length, and the regeneration of the PMD distribution of test fibers fabricated by splicing constituent fibers with known PMDs was successful. Surprisingly, the regenerated PMD distribution along the fiber length shows a linear accumulation of constituent fiber PMD in the short range of 6 km. The reverse-direction measurements show a reasonable regeneration of what is assumed to be a linear accumulation along the fiber length, which strongly suggests that the PMD distribution along the fiber shows a linear accumulation rather than a root-length accumulation in relatively short fibers with smaller PMD     

A new method for fiber chromatic dispersion measurement with microwave interference effect

The chromatic dispersion (CD) is a key parameter for optical fibers. Based on the microwave interference effect, a new method for CD measurement of optical fibers is proposed. The radio frequency (RF) signals carried by two light-waves with different wavelengths transmit through the dispersive optical fiber under test. After photo-detector they interfere with each other due to the different phase shifts induced by the CD of fiber. The CD can be obtained by monitoring the changing interference RF power with scanning the wavelength of tunable laser source. The CD values of single mode fiber and dispersion compensating fiber are measured within the wavelength range from 1525 to 1605 nm. The common phase shift method is used to measure the CDs of the two types of fiber, which demonstrates the feasibility and veracity of the proposed method.     

一种便携式激光多普勒测速光学系统的设计

为了将激光多普勒测速技术应用于野外流体速度测量,设计了一种基于舣光束模式的激光多普勒测速光学系统,采用光纤耦合半导体激光器作为光源,通过保偏光纤耦合器、保偏光纤准直器以及非球面透镜来实现激光的分束、准直与聚焦,形成干涉条纹,并利用接收透镜、针孔光阑以及雪崩光电二极竹检测多普勒信号光.结果表明,所设汁的光学系统的空间分辨...     

大粗糙度表面激光散射特性实验研究

本文利用激光散射自动测量系统,对经喷丸处理后的钢基粗糙表面及其喷漆表面的后向激光雷达散射截面(LRCS)进行了测量。测量波长分别为λ=633nm和λ=904nm.在λ=904nm,利用粗糙面电磁散射理论的基尔霍夫方法对上述样片进行了理论计算,其中将粗糙表面视为双尺度模型,根据驻留相位法和标量近似法理论计算双尺度模型随机粗糙表面的散射强度角分布,其理论值与实验测量结果有较好的吻合。     

Limitations imposed by stimulated Raman scattering of 1550 nmhigh-energy pulse transmission

The limitations imposed by stimulated Raman scattering on 1550 nm high-energy pulse transmission in single-mode optical fiber are investigated. The generation of a Stokes pulse from an input pulse with peak power up to 60 W and duration on the order of 10 ns is experimentally studied and numerically simulated. This is the first demonstration of Stokes pulse generation in optical fiber from pump pulses within the 1550 nm telecommunications window. Experiment and theory show that there is an optimum input power for a given pulse duration and distance that maximizes the energy transmitted over long fibers     

Noncontact calibration of optical fiber cladding diameter usingexact scattering theory

A new, contactless and nondestructive method for measuring the diameter of an optical fiber is described which has 10 nm sensitivity. In this method, polarized laser light is backscattered from the fiber, perpendicular to its axis. The measured intensity shows excellent agreement with calculations from an exact scattering theory, and reveals both the refractive index and diameter of the fiber. The high sensitivity of this method results from the intrinsic interferometric properties of the fiber itself, and depends on the wavelength of the coherent light source only. If the fiber's circumference is circular, the high sensitivity of this method leads to an absolute calibration accuracy of 10 nm of the fiber diameter     

Distributed beatlength measurement in single-mode fibers with optical frequency-domain reflectometry

The polarization dependence of the coherent detection in optical frequency-domain reflectometry can be exploited to measure the local beatlength along an optical fiber. Reproducibility of the results is given for high and low polarization-mode coupling fibers, and the influence of several effects on beatlength measurement precision, such as spatial reflectometer resolution, fiber twist, and the presence of circular birefringence, is discussed. The experimental results seem to indicate that the typical assumption that the fiber birefringence can be treated as purely linear might not be fully justified. Beatlength overestimates of 10% and more can result.     

多模与单模光纤级联系统对激光束的传输

分析了激光束在光纤中的非线性传输损耗,理论上证明了受激布里渊散射(SBS)是光纤传输能力的主要限制因素;实验上在532nm波段对长度为5m,纤芯半径为1.75μm,数值孔径(NA)为0.11的单模光纤的传输能力进行了测定,结果与理论一致。采用模场耦合理论,推导出多模光纤与单模光纤的直接耦合效率表达式,计算得到耦合效率与所选用的多模光纤和单模光纤的纤芯芯径之间的模拟关系。激光器输出波长为532nm;多模光纤的数值孔径为0.11,纤芯半径为12.5μm;单模光纤的数值孔径为0.11,纤芯半径为1.75μm,实验结果与理论基本吻合。根据理论和实验结果,设计出多模光纤与单模光纤混合传输方案,在柔性传输较高激光功率的同时可以得到高光束质量。     

基于高频微波技术的分布式布里渊光纤温度传感器

提出了一种基于分布式布里渊光纤传感系统的温度快速测量方案。该方案基于外差相干检测原理,利用高速脉冲检波管对布里渊散射信号进行直接探测,从而缩短了测量时间;并结合累加平均与小波变换技术,减小了布里渊散射信号中的噪声,通过对去噪后的信号进行解调实现了长距离温度测量。实验结果表明,在24.8km的长度范围内,温度测量误差小于3℃,测量时间小于3s。