偏振模色散及偏振相关损耗对光传输链路相关特性的影响

在同时考虑偏振模色散(PMD)及偏振相关损耗(PDL)情况下，分别通过理论和蒙特一卡罗方法研究了光传输链路的输出信号偏振态相关函数。首先，从理论上得到了光传输链路的输出信号偏振态相关函数的解析表达式，而后，利用蒙特一卡罗方法进行了模拟研究，理论和模拟的结果能很好地吻合。研究结果表明，当光传输链路的偏振模色散值不变时，随着传输链路偏振相关损耗的增大，输出偏振态归一化自相关函数的线宽变宽；而在光传输链路的偏振相关损耗一定的情况下，随着光传输链路的偏振模色散的增大输出偏振态归一化自相关函数的线宽变窄。     

外界条件对FBG反射偏振相关损耗特性的影响

利用光纤光栅反射偏振相关损耗对外力场信息的变化进行监测,提高了测量性能,并研究了光纤布拉格光栅(FBG)反射偏振相关损耗(RPDL)随外界条件的变化。运用耦合模理论得出外界条件变化量与反射偏振相关损耗间的关系式,并模拟了温度、应力、压力的改变对反射偏振相关损耗谱线的影响。仿真结果表明:光纤光栅反射光的偏振相关损耗对外界温度、应力的变化不敏感,但却明显地依赖外界压力的变化。     

光栅参数对线性啁啾光纤光栅偏振特性的影响

研究了单模线性啁啾光纤光栅的偏振相关损耗特性。运用耦合模理论和传输矩阵分析法推出了反射光的偏振相关损耗,并模拟了光栅的反射谱和偏振相关损耗随光栅参数和双折射量的变化曲线。模拟显示双折射值的变化对啁啾光栅偏振相关损耗的影响非常显著, 尤其是在带边比较陡峭时。啁啾光栅的偏振相关损耗也受光栅的啁啾系数和调制深度的影响。这表明线性啁啾光栅的偏振相关损耗不光依赖光栅双折射量,还依赖其啁啾系数等其他参数。实验结果与理论模拟基本吻合。     

偏振相关损耗与偏振模色散的特性影响及偏振模色散的最新测量方法

研究在偏振模色散（PMD）和偏振相关损耗（PDL）共同作用情况下光传输链路的输出信号偏振态相关函数。研究表明，在光传输链路中偏振模色散的值和偏振相关损耗的值分别不变的情形下。输出偏振状态相关函数的线宽随着偏振相关损耗的增大而增大，随着偏振模色散的增大而变窄。虚拟广义米勒矩阵测量方法（VGMMM）结合了矩阵测量法和微分测量法的优点并克服了它们的不足。可以在对输入偏振态不确定的情况下使用相对较大的频率间隔获得低噪声、高精度的PMD数据，所测结果的准确度高于其它方法。     

VCSEL偏振相关特性的实验研究

利用一套自己研制的实验装置对VCSEL的偏振相关特性进行了研究，包括偏振相关静态LI曲线、光谱以及时间响应等，分析了偏振模式分配噪声的产生机理。在此基础上提出了实现完全偏振稳定的设计思路。     

基于压缩感知的偏振鬼成像系统

偏振鬼成像系统结合了强度和偏振探测,扩展了鬼成像系统的信息量,可以进行有效的目标识别和探测。常规相关偏振鬼成像系统需要大量采样数,且复原结果信噪比低。为此提出基于缩感知的偏振鬼成像系统,利用系统获取物体的强度和偏振参数,采用压缩感知算法来反演获取物体的强度和偏振信息。利用仿真实验,采用具有相同反射率但不同偏振特性的物体进行研究,结果表明采用压缩感知算法可以在很少的采样数下获取高质量的物体强度和偏振信息,提高了系统的实时性,并与相关算法进行了对比。最后采用图像融合算法对强度和偏振信息进行了融合,通过融合信息可以有效地进行多种物体的识别。     

单层二氧化钛薄膜的偏振散射特性

为了用散射法研究单层薄膜表面粗糙度的变化规律,以光学薄膜矢量光散射理论为基础,分析了单层二氧化钛薄膜分别在完全相关和完全非相关模型下的偏振双向反射分布函数,以及P偏振入射光引起的P偏振的BRDFpp随散射方位角的变化关系。理论研究结果表明:随着散射方位角的变化,P偏振入射光引起的P偏振的BRDFpp强烈依赖于膜层界面粗糙度的相关特性。在完全相关模型下,随着入射角的增加,BRDFpp随着散射方位角变化时所出现的谷值会随着入射角的增加而减小。     

基于线偏振扫描法的偏振相关损耗测试仪设计

使用线偏振扫描法来对光无源器件的偏振相关损耗进行测量,采用了基于单片机的步进电机带动偏振片旋转。重点阐述光路设计和偏振模块设计,并且搭建实验装置验证了设计的结果,偏振相关损耗的测量误差在±0.02dB。     

同时偏振成像探测系统的偏振图像配准研究

同时偏振成像探测技术是一种新型的偏振成像探测技术,它能在同一个探测器上同时获得被探测目标0、45、90、135 4个偏振方向的偏振强度图像。为了准确获取被探测目标的偏振信息,这４幅图像的配准显得尤为重要。为了使配准精度达到0.1个像元,结合同时偏振成像探测系统的成像方式,提出了一种基于空域和频域互相关的偏振图像配准方法。该方法使用硬件和软件相结合的方式完成图像的配准。首先使用空域互相关的算法实现图像的像元级粗配准;然后使用频域互相关的像元级配准算法进行像元级精配准;最后使用频域互相关的亚像元配准算法实现偏振图像的亚像元级配准。     

全光纤在线偏振参量测试系统

设计和研制了一套全光纤在线偏振参量测试系统,该系统由全光纤偏振控制器、全光纤在线偏振仪等组成.系统的光路完全由光纤构成,没有插入分立器件.通过数据采集卡和Labview编程,实现了全光纤在线偏振参量测试系统对偏振态的准确控制和对斯托克斯矢量的实时、准确和高速的测量.该系统能实现对光的偏振态、偏振度、消光比和偏振相关损耗等偏振参量的测量,并能实现偏振态监控和偏振稳定的功能.     

Surface-grating VCSELs with dynamically stable light output polarization

It has been shown recently that the polarization of single- and multimode vertical-cavity surface-emitting lasers (VCSELs) can be defined and stabilized very effectively with a monolithically integrated surface grating. Orthogonal polarization suppression ratios of 20 dB or more have been achieved even for transverse multimode devices. It has not been investigated in detail yet whether these lasers are also polarization stable under high-frequency modulation. We show that surface-grating VCSELs remain polarization stable for digital high-frequency modulation up to 10Gb/s, modulation amplitudes of up to 1.5 V/sub pp/, and different modulation patterns. Under modulation, neither polarization-resolved time traces nor polarization-resolved spectra nor the power ratio of the two polarizations indicate a deterioration of the polarization properties compared to the static case.     

Polarization-resolved relative intensity noise measurements of a vertical-cavity surface-emitting laser subjected to strong optical feedback

We experimentally measure the polarization-resolved relative intensity noise (RIN) in two orthogonal polarization states of a vertical-cavity surface-emitting laser (VCSEL) subjected to strong optical feedback. A comparison is made with the RIN of solitary VCSEL. Optical feedback is shown to enhance the RIN in one polarization direction while suppressing the RIN in the orthogonal polarization. The RIN in the dominant polarization mode exhibits complementary behavior to the RIN in the suppressed polarization mode.     

表面光栅垂直腔面发射激光器偏振特性研究

研究了表面光栅结构对垂直腔面发射激光器(VCSEL)的偏振控制作用。引入表面光栅后,对不同刻蚀深度下的偏振相关的镜面损耗进行了仿真,结果表明表面光栅刻蚀深度在44~130 nm范围内均可实现稳定偏振,具有较大的工艺容差。表面光栅VCSEL在基横模工作状态下偏振抑制比(Orthogonal Polarization Suppression Ratio, OPSR)超过20 dB,偏振光谱峰间偏振抑制比达到40 dB,且在多横模状态也实现了有效的偏振控制。为了进一步验证光栅对偏振控制的效果,制作了方向互相垂直的两种表面光栅,具有这两种方向光栅的VCSEL的OPSR均达20 dB以上。测试分析表明表面光栅是VCSEL实现稳定偏振的一种有效手段。     

Far- and near-field investigations on the lasing modes intwo-dimensional photonic crystal slab lasers

We present experimental investigations on the lasing modes in two-dimensional (2-D) hexagonal cavities defined by photonic crystals on slab waveguide structures. The far-field emission patterns and near-field intensity distributions of the lasing modes are analyzed in polarization-resolved 2-D angular distribution measurements and spectrally resolved near-field scanning optical microscopy. The far- and near-field analyses result in identification of the various lasing modes and their subsequent classification into one- and two-dimensional modes. In the one-dimensional modes oscillating between two parallel boundaries of the cavities, longitudinal and transverse modes are identified and found to have transverse-electric polarization. In the two-dimensional modes oscillating two-dimensionally in the cavities, various modes including whispering-gallery-like modes are observed and found to exhibit various polarization states     

Polarization Dynamics of Current-Modulated Vertical-Cavity Surface-Emitting Lasers

We study the dynamics of vertical-cavity surface-emitting lasers (VCSELs) with direct current modulation in the framework of a model for index-guided VCSELs that takes into account two orthogonal linear polarizations. We analyze the effect of current modulation near the polarization switching (PS) of type I, from the high to the low frequency polarization, and near the PS of type II, from the low to the high frequency polarization. We find that the oscillations of the total power are as those of a single-mode laser, unaffected by the underlaying polarization coexistence or polarization competition. We also study the small-signal modulation response in the Fourier domain, for modulation dc values near the PS point. Close to type I PS the response of the total power as well as the response of the orthogonal polarizations has the same functional dependency on the modulation frequency, and can be fitted by the response function of a single-mode laser. Close to type II PS, polarization competition is a significant process at low modulation frequencies. The polarization-resolved modulation response displays features at low frequencies that are not present in the response of the total power, which is as that of a single-mode laser. The dynamics becomes increasingly complex as the modulation amplitude grows, and there is multistability of solutions.     

Polarization-Resolved Modulation Response of Single-Transverse-Mode Vertical-Cavity Surface-Emitting Lasers

The small-signal modulation response of vertical-cavity surface-emitting lasers (VCSELs) is studied numerically, based on the spin-flip model. A detailed characterization of the influence of various parameters, such as the dichroism, the birefringence, the spin-flip rate and the noise level is done. The analysis is performed in regions of the parameter space where the operating conditions, in the absence of modulation, are such that there is either stable single linear polarization, or bistability of two orthogonal linear polarizations or polarization instability. In the instability region the intensities of the orthogonal polarizations display anticorrelated self-sustained oscillations that result in a complex small-signal modulation response, exhibiting multiple resonance peaks with frequencies that vary with the injection current and the spin-flip rate. In contrast, in parameter regions where there is stable single polarization the modulation response of the total intensity is as that of a single-mode laser, exhibiting a conventional single-resonance peak, and is almost not influenced by the value of the spin-flip rate. Polarization mode-hopping results in a distortion of the polarization-resolved modulation response at low frequencies.      

Extraction of bonding strain data in diode lasers from polarization-resolved photoluminescence measurements

A technique to determine strain in diode lasers by matching measured polarization-resolved photoluminescence to a finite element method model is described. The code is shown to be able to fit well a finite element model with degree of polarization measurements to extract strain information from diode lasers and predict strain values owing to die bonding. It is useful in characterizing die bonding processes and in detecting solder voids which can impact the reliability of devices. Using the code, it is demonstrated that there are differences in the die bonding strain from different die attachments. The bonding strain from InP chips die bonded to copper and silicon chip carriers using gold–tin solder are examined.     

Influence of anisotropies on transverse modes in oxide-confinedVCSELs

We present a comprehensive fully vectorial model for the cavity eigenmodes of oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with the details of their complex structure. It includes device-inherent symmetry-breaking mechanisms like noncircular geometries and material anisotropies related to the elasto-optic and electro-optic effect. The latter is accounted for in the model starting from the material and doping profiles. We compare these theoretical results with experimental findings of spectrally and polarization-resolved transverse mode nearfields of oxide-confined VCSELs with two different aperture diameters. Within a parametric study of the influence of aperture anisotropies, we are able to calculate frequencies and gains of all transverse mode families, their polarization dependence and their spatial mode profiles which are in good agreement with the experimental findings     

Design and ASE characteristics of 1550-nm polarization-insensitivesemiconductor optical amplifiers containing tensile and compressivewells

The polarization dependence of 1550-nm semiconductor optical amplifiers (SOA's) containing tensile and compressive wells has been investigated both theoretically and experimentally. Our model to predict the polarization-resolved (TE and TM) gain spectra of these structures has been confirmed by amplified spontaneous emission measurements. It is found that there can be appreciable carrier redistribution between the two types of wells when the tensile layers have the large thickness (greater than 100 Å) needed for gain at wavelengths around 1550 nm. This carrier redistribution can significantly modify the ratio of the gains for different polarizations, in particular, decreasing the TM gain with respect to the TE gain, and, hence, is an important design consideration. We use our model and experimental data to explore design criteria for 1550-nm polarization-independent SOA's     

Digital optical signal processing with polarization-bistable semiconductor lasers

The operations of a complete set of optical AND, NAND, OR, and NOR gates and clocked opticalS-R, D, J-K,andTflip-flops are demonstrated, based on direct polarization switching and polarization bistability, which we have recently observed in InGaAsP/InP semiconductor lasers. By operating the laser in the direct-polarization-switchable mode, the output of the laser can be directly switched between the TM00and TE00modes with high extinction ratios by changing the injection-current level, and optical logic gates are constructed with two optoelectronic switches or photodetectors. In the polarization-bistable mode, the laser exhibits controllable hysteresis loops in the polarization-resolved power versus current characteristics. When the laser is biased in the middle of hysteresis loop, the light output can be switched between the two polarization states by injection of short electrical or optical pulses, and clocked optical flip-flops are constructed with a few optoelectronic switches and/or photodetectors. The 1 and 0 states of these devices are defined through polarization changes of the laser and direct complement functions are obtainable from the TE and TM output signals from the same laser. Switching of the polarization-bistable lasers with fast-rising current pulses has an instrument-limited mode-switching time on the order of 1 ns. With fast optoelectronic switches and/or fast photodetectors, the overall switching speed of the logic gates and flip-flops is limited by the polarization-bistable laser to < 1 ns. We have demonstrated the operations of these devices using optical signals generated by semiconductor lasers. The proposed schemes of our devices are compatible with monolithic integration based on current fabrication technology and are applicable to other types of bistable semiconductor lasers.