【作者】 何晓颖；

【导师】 黄德修； 余永林；

【作者基本信息】 华中科技大学 ， 光学工程， 2009， 博士

【摘要】 Bragg光栅和可调谐半导体激光器是全光通信网络的重要组成部分之一，为实现可重构的智能光网络提供了保障。同时，它们也是光纤传感和测量领域中的关键器件之一。Bragg光栅和可调谐半导体激光器，凭着广泛的应用前景，受到了国内外业界人士的广泛关注。本论文围绕Bragg光栅及其在可调谐半导体激光器中的应用，展开了系统而深入的研究，具体研究内容如下：(1)根据Bragg光栅的傅立叶变换理论，推导出了取样光纤光栅、两种高斯切趾的取样光纤光栅和间插式取样光纤光栅的反射谱包络表达式，并且通过传输矩阵法验证了该表达式的准确性。不仅分析了光栅中的各个参数对反射谱包络及其旁瓣的影响，还详细地研究了温度和应力的变化对取样光纤光栅反射谱的影响。(2)根据带相移间插取样光纤光栅反射谱包络表达式，分析了带相移的间插取样光纤光栅中子光栅相移、光栅区长度、间插长度等对反射谱包络的影响。为设计顶部平坦的间插取样光栅提供了理论依据。(3)基于傅立叶变换的线性不变性和可逆变换性，提出了多反射谱包络级联技术。该技术不仅能加密取样光纤光栅的谱信道，而且还能够对光栅的空间物理结构加密。利用该技术，提出了两种新型的多反射谱Bragg光栅——数字级联光栅和连续间插取样光栅。这两种新型的Bragg光栅不仅能提供顶部平坦的反射谱包络，还可以让光栅保持高的峰值反射率。(4)将线性激光器传输法与等效腔法结合，建立了可调谐取样光纤光栅外腔半导体激光器的数值仿真模型。模拟了该激光器的静态特性，如：阈值特性、P-I曲线、光谱线宽、激射光谱、静态调谐特性和边模抑制比。为设计利用Vernier调谐原理的外腔可调谐半导体激光器提供理论基础。(5)通过理论模拟取样光纤光栅外腔半导体激光器的调谐曲线、边模抑制比和输出光功率，观测到了存在于所有可调谐半导体激光器中的非线性现象，如：调谐迟滞现象、边模抑制比和输出光功率谱不对称现象。为了分析这些非线性现象的起因，将半导体中的非线性效应(如：交叉增益调制、交叉相位调制、四波混频)考虑到该激光器的理论模型中。分析了内部的物理参数和半导体中的四波混频效应对这些非线性现象的影响。为研究可调谐半导体激光器内部的非线性机理提供了理论基础。(6)为了抑制可调谐取样光纤光栅外腔半导体激光器的非线性效应，在该激光器的外部光栅中引入了间插技术和切趾技术。旁瓣的抑制能够一定程度上抑制非线性现象，增加可调谐半导体激光器的调谐带宽。间插技术的处理能够让取样光纤光栅的外腔可调谐半导体激光器获得18．4 nn调谐带宽。并在整个调谐范围内，其光功率输出达到10 dBm，边模抑制比达到40 dB。(7)建立了SG-DBR激光器的理论模型；研究了SG-DBR激光器的静态特性。通过理论模型的建立，发现可调谐半导体激光器的反射端面同取样光栅之间形成了一个隐形的F-P谐振腔。该隐形的F-P谐振腔对SG-DBR激光器的静态特性有很大的影响，特别是调谐曲线。(8)提出了基于半导体材料数字级联光栅的两种设计结构，一种是改变级联光栅的光栅周期；另一种改变级联光栅的有效折射率。这两种方案都能够获得顶部平坦的反射谱。还提出了三种可实施的制作方法：全息曝光、电子束曝光、和纳米压印。(9)提出了一种新型的可调谐DBR激光器——数字级联DBR激光器。模拟结果表明，该设计获得了将近50 nm的波长调谐范围，并且在整个调谐区域内，边模抑制比可达到35 dB，输出功率维持在10 dBm左右，且具有很好的输出光功率均衡性(0．6 dB)，且对端面的反射率有很高的容忍度。更多还原

【Abstract】 Bragg gratings and tunable semiconductor lasers are some of essential devices inoptical networks,and provide important guarantee for the reconfigurable AutomaticallySwitched Optical Network (ASON).They also are the key components for optical fibersensors and measurements.Due to these wide applications,many scientists and expertshave been attracted to research on the Bragg gratings and tunable semiconductor lasers.Inthis dissertation,Bragg gratings and their applications on tunable semiconductor lasers havebeen explored and investigated.The main contents are as follows:(1)Due to the Fourier transform theory on the fiber Bragg grating,the analyticalexpressions on the sampled fiber grating,Gauss-apodized sampled fiber grating,sampledGauss-apodized fiber grating,and interleaved sampled fiber grating withψphase shift havebeen presented.Accuracy of those expressions has been verified by a good agreement withtheir reflection spectrum obtained by the transfer matrix method.Impacts of parameters inthe sampled fiber grating on the reflection spectrum envelope and sidelobes have beenstudied.The impacts of temperature and stress on reflection spectrum of the sampled fibergrating have also been discussed in detail.(2)Based on the analytical expression of interleaved sampled fiber grating,impacts ofshift phases of the inserted sub-grating,grating length,as well as interleaved length on itsreflection spectrum envelope have been analyzed.It provides theoretical reference to designthe interleaved sampled fiber grating in detail.(3)According to the linear invariability and reversibility of Fourier transform theory,anovel multiple reflection spectrum envelope concatenated technology has been proposed.The proposed technology can densify spectral channels of sampled gratings with fixed peakspace,as well as spatially physical corrugation of structure.Using such technology,twomulti-peak Bragg gratings have been designed:one is the digital concatenated grating;theother is the consecutive interleaved sampled grating.These proposed gratings can provide afiat reflection spectrum envelope and high peak reflectivity.(4)The theoretical simulation model of the tunable sampled fiber grating externalcavity semiconductor laser has been built by combining the equivalent reflection cavitytheory with the transmission line laser theory.Due to this model,the steady-state propertiesof sampled fiber grating external cavity semiconductor lasers,such as thresholdcharacteristics,P-I curves,line-width,output spectra,static wavelength tuning curve,as wellas SMSR,have been simulated and analyzed.It is useful for designing tunable external cavity semiconductor lasers with Vernier tuning principle.(5)The nonlinear phenomena such as asymmetric side mode suppression ratio orpower characteristics and tuning hysteresis phenomena are the ubiquitous phenomena intunable semiconductor lasers,which have been observed in the sampled fiber gratingexternal cavity semiconductor lasers by studying its static characteristic curves,such as thewavelength tuning curves,side mode suppression ratio curves,output power curves and soon.In order to analyze the origin of these nonlinear phenomena,the nonlinear effects insemiconductor (e.g.cross-gain modulation effect,cross-phase modulation effect,and fourwave mixing effect)have been considered in the theoretical model of the sampled fibergrating external cavity semiconductor laser.Influence of its internal physical parameters andthe four wave mixing effect on nonlinear phenomena of such laser are analyzed anddiscussed.It is helpful for exploring the internal nonlinear mechanism of tunablesemiconductor lasers.(6)In order to suppress the nonlinear effect in such sampled fiber grating extemalcavity semiconductor laser,apodization and interleaved technology have been introducedinto the external sampled fiber grating of such laser.The suppression of side-lobes cansuppress the nonlinear phenomena in the sampled fiber grating external cavitysemiconductor laser and increase its tuning range.An interleaved technology can make suchlaser obtain 18.4 nm tuning range.In its whole tuning range,side mode suppression ratio of40 dB and output power around 10dBm have been obtained.(7)The theoretical model of the SG-DBR laser has been established based on thetransmission line laser theory.The steady-state characteristics of the SG-DBR laser havebeen discussed.It is found that the invisible F-P cavity between anti-reflection coating andsampled grating has existed in the SG-DBR laser.Such invisible F-P cavity has taken largeinfluences on the steady-state characteristics of the SG-DBR laser,especially on its tuningcurves.(8)Two designs of the digital concatenated grating on the semiconductor materialhave been proposed for providing the top flat reflection spectrum envelope.One is forchanging the grating period of the conctenaed sub-grating;the other is for changing theeffective material index of the sub-grating.Three manufacture methods of these digitalconcatenated gratings have been proposed,which are holography method,electron beamlithography,and nanoimprint lithography.(9)A novel digital concatenated grating DBR laser has been proposed,for obtainingwidely tuning range (＞50 nm),high side mode suppression ratio (＞35 dB),and high output power (～10 dBm)with low power varation (0.6 dB).Such proposed laser has high outputpowers with small power variation,and high toleration on facet reflectivity.更多还原