高宽带光收发器件的技术现状

介绍了光收发器技术在光纤传输系统中的应用现状，重点叙述了光外调制技术（比如电吸收型调制器、LiNbO3调制器等）、单行载流子光电管（UTC－PD）的发展水平，指出高宽带、高速率、高集成化是光收发器件发展的必然趋势。     

高速集总型双耗尽电吸收调制器的研制

设计并研制了一种新的直脊波导集总型电吸收调制器——集总型双耗尽电吸收调制器（D-EAM）。同时,作为实验对照组,还制备了一种普通有源区结构的电吸收调制器（N—EAM）。两种器件的测试结果对比分析表明,D-EAM的电容明显要小于N—EAM。脊波导长度为250μm,宽度为2．5弘m的D-EAM在－3V偏压下电容为0．225pF,对应的调制带宽估算为28．3GHZ;1550nm输入波长条件下,D-EAM在偏压为－1V至－2V之间调制效率最大,达到10dB／V,而－3V、－6V下的调制深度分别为22dB和26dB,满足40Gbit／s光纤通信要求。     

基于时域法的单条形InP/InGaAsP-EAM调制器的行波电极的仿真与实验研究

行波电极(Traveling wave electrode,TW),是目前广泛采用的一种电极结构,可缩短光载波与调制信号的互作用长度,可有效避免分布电容(Contribution capacity,CR)对调制带宽的限制.基于时域法设计、分析了InP/InGaAsP-EAM调制器行波电极,并与实际制作的EAM的行波型TW进行了特征阻抗Zc、损耗系数α对比,结果表明用时域法设计、计算的TW的特征阻抗、损耗系数与实测的结果符合的较好,特征阻抗约为45Ω,在0～20 GHz的频率范围,损耗系数α小于4 dB/mm.     

GaAlAs／GaAs欧量子阱增益耦合型DFB激光器电吸收型调制器单片光子…

我们在国际上率先提出将增益耦合分布反馈式（ＧＣ－ＤＦＢ）半导体激光器作为激光器／调制器单片集成器件的光源，为了简化制作工艺，进一步提出激光器的有源层与调制器波动共用同一组分和同一结构，本理论上分析了新型器件的可行性，优化设计了器件结构，在此基础上，采用金属有机化合物化学汽相外延技术（ＭＯＣＶＤ）在国际上首次研制成功了该种增益耦合型ＤＦＢ激光器／电吸收型调制器单片光子集成器件，器件电流为３５ｍＡ。     

TW—SLA在耦合腔锁模激光器中的调制特性

本文将行波半导体激光放大器（TW－SLA）引入耦合腔锁模激光器中，详细分析了外腔的有效反射系数。结果表明：TW－SLA的增益饱和及自相位调制对光脉冲具有调制特性，利用这类耦合腔激光器可实现自启动锁模以及具有获得超短光脉冲的可能性。     

MQW EA调制器用于短脉冲光子源驱动条件的优化设计

本文分析了多量子阱电吸收调制器（MQW EAM）的非线性损耗特性,从时域和频域两个方面讨论了MQW EAM驱动条件与输出光脉冲特性的关系.数值计算结果证明EAM产生的脉冲形状比较接近Gauss脉冲,具有较小的啁啾,接近于变换限的光脉冲,十分适用于高速时分复用系统.     

光发射机中MZ型波导调制器产生CTB的分析

AM－CATV外调制光发射机中的MZ型波导调制器，其转移特性呈正弦曲线。当多路信号同时调制时，将产生组合二次失真（CSO）和组合三次差拍（CTB）。本文对CTB进行了理论分析，并对我国450、550MHz二种CATV系统调制时的CTB进行了计算。这对非线性补偿电路的设计具有一定的指导价值。     

弯波导吸收区结构1．3μm InGaAsP／InP超辐射发光二极管的设计

本文用束传播方法（ＢＰＭ）设计了具有弯曲波导吸收区结构１．３μｍＩｎＧａＡｓＰ／ＩｎＰ超辐射发光二极管（ＳＬＤ），分析了不同吸收区长度Ｌａ和弯曲的曲率半径Ｒ对ＳＬＤ特性的影响，给出了直观的结果，并进行了优化设计。在假定吸收区后端面反射率为１，和忽略吸收区内的吸收损耗的条件下，取ｄ＝０．２μｍ，ｗ＝２μｍ，Ｌｐ＝４００μｍ，Ｌａ＝２００μｍ，Ｒ＝５００μｍ，Ｉ＝２００ｍＡ，经吸收区反射耦合回有源区内的光与有源区前端面入射光的强度比率仅为９．５×１０－３。     

基于电吸收调制器的40Gb/s光学3R再生器模型设计及性能分析

提出了一种结构简单而且性能稳定的40Gb/s光学3R再生器,它由基于电吸收调制的两个波长转换器与基于行波电吸收调制器的光时钟恢复器构成。     

GaAlAs／GaAs多量子阶增益耦合型DFB激光器／电吸收型调制器单片光子集成器件

我们在国际上率先提出将增益耦合型分布反馈式（ＧＣ－ＤＦＢ）半导体激光器作为激光器／调制器单片集成器件的光源．为了简化制作工艺，进一步提出激光器的有源层与调制器波导共用同一组分和同一结构．本文从理论上分析了该新型器件的可行性，优化设计了器件结构．在此基础上，采用金属有机化合物化学汽相外延技术（ＭＯＣＶＤ）在国际上首次研制成功了该种增益耦合型ＤＦＢ激光器／电吸收型调制器单片光子集成器件．器件阈值电流为３５ｍＡ，在—５Ｖ调制电压下消光比达５ｄＢ．静态调制过程中，激射波长与阈值没有变化．     

Performance analysis of 2-D time-wavelength OCDMA systems with coherent light sources: code design considerations

The performance of two-dimensional (2-D) time-wavelength (TW) optical code-division multiple access systems at both physical and data link layers is considered in the presence of a multitude of noise sources. Particular consideration is given however to both beat noise (BN) and multiple-access-interference effects. A general procedure for calculating BN is presented. Comparisons between several 2-D TW codes comprising single-pulse-per-column/row and multiple-pulse-per-column/row strategies are performed. Results reveal that BN is strongly dependent on the code properties and the distribution of wavelengths within a code. Several aspects for 2-D TW code design are presented that mitigate the effect of BN.     

High-speed shielded velocity-matched Ti:LiNbO3 opticalmodulator

A shielded velocity-matched Ti:LiNbO₃ optical modulator is investigated, focusing on the characteristics of the traveling-wave (TW) electrode and the optical waveguide. The optical waveguide is analyzed and its parameters are determined using the newly developed modified-step-segment method (MSSM). The TW electrode is analyzed using the second-order triangular element quasi-TEM finite element method (FEM). By taking the thickness of the coplanar waveguide (CPW) traveling-wave (TW) electrode into consideration, it is confirmed that there is an optimum overlaid layer thickness for a given electrode thickness. It is also shown that very wide modulation bandwidth can be attained by using the optimum CPW TW electrode thickness and overlaid layer thickness     

Gain saturation properties of a semiconductor gain medium withtensile and compressive strain quantum wells

Gain saturation properties of a multiple-quantum-well structure with both tensile and compressively strained quantum wells are investigated analytically. This type of structure has recently been experimentally demonstrated to serve as a basis for the implementation of a two-polarization/two-frequency laser and polarization insensitive travelling wave(TW) amplifier. The performance of these devices strongly depends on the interaction between the TE and TM gains of the structure. The gain medium model appropriate for this type of structure is developed and the rate equation approach is used to describe the saturation properties of TE/TM gains and the coupling between the TE and TM gains due to gain saturation. The minimum amount of coupling between the two is governed by the basic symmetry of the light-hole wavefunction which interacts with photons of both polarization: photon cross-coupling. The finite rate of carrier escape from the quantum wells provides for carrier induced coupling between the populations of the two well types and therefore also couples TE and TM gains: carrier cross-coupling. The performance of a polarization insensitive amplifier, laser, and polarization control element is evaluated as a function of the amount of carrier cross-coupling, which is a structure dependent parameter. A structure with high degree of cross-coupling is desirable for polarization insensitive TW amplifier, while two-polarization lasers and polarization control elements require minimum cross-coupling     

Enhanced electrooptic modulation efficiency utilizing slow-waveoptical propagation

The use of slow-wave optical propagation to promote highly efficient electrooptic modulation of light is investigated theoretically. The proposed modulators utilize a traveling wave (TW) design in which a grating integrated with a single-mode waveguide induces coupling between forward- and reverse-propagating waves. This contradirectional coupling leads to a reduction in the average optical propagation speed in the forward direction. The “slow” waveguide structures provide two features which facilitate improved modulator performance over conventional “fast” TW designs: (1) optical/microwave velocity matching in substrates with high electrooptic coefficients and dielectric constants and (2) enhancement of electrooptic phase shift due to the “dwell time” of the light in the modulation region. For the ideal case of perfect velocity matching, these two factors lead to a potential improvement of nearly an order of magnitude in electrical power dissipation over velocity-matched designs in the conventional lithium niobate (LN) substrate material. Additional orders-of-magnitude improvement in the required electrical power could result from the use of tungsten bronze substrates such as strontium barium niobate (SBN), which have such higher electrooptic coefficients than LN. The prediction of a large reduction in electrical power dissipation is confirmed by calculations for specific slow-wave designs utilizing multireflector etalons in SBN, although response speed limitations result from the fact that perfect velocity matching is not achieved     

Correlation of theory with experimental SOAs

Predictions for the near-traveling wave amplifier (NTWA) with multiple-quantum-well structures have been developed. The continuity equation for quantum wells (QWs) with high carrier densities is combined with the amplifier TW gain equation expressed in terms of stimulated lifetime. This formulation allows the signal gain to be related to the bias current and the optical input signal through Fermi energies. The charge neutrality condition also plays an important role for high carrier density QW amplifiers. Auger recombination and heating effects are incorporated as essential components of the model. Experimental measurements of gain versus bias current and output power for both /spl lambda/= 850- and 1550-nm devices are found to be very well matched by the calculated results.     

Fabrication,Functionalities and Applications of Transparent Wood: A Review

Transparent wood (TW)-based materials have increasingly become the focus of researchers worldwide owing to their superior physico-chemical-optical properties, sustainable nature, as well as the fact that they are highly accommodating frameworks that can act as building blocks to readily explore a vast range of potential functionalities, holding great potential to displace glass and plastics in their various respective applications. The integration of multiple functionalities into TW has been undertaken to fulfill the demands of prospective sophisticated applications through the utilization of functional fillers or coatings. Herein, the up-to-date foundational developments and reports concerning emergent TW composites and coatings from a perspective of fabrication-functionality-application are comprehensively summarized, with a particular focus on seven specific functionalities; i) solar control; ii) chromically-responsive, iii) electrically-conductive, iv) shape-memory active; v) flame-retardant; vi) electromagnetic interference shielding; and vii) aesthetics. The potential applications of TW with these functionalities are also discussed. Finally, the current challenge with TW is addressed, as well as the future developments required for eventual real-world application.     

Bistable traveling-wave oscillations of ion ring laser

The dc-excited argon ion laser in an optical ring resonator has been found to oscillate spontaneously in one circulatory direction, for all but a relatively narrow range of gain levels above threshold. Near threshold the TW oscillations occur in the direction opposite that of the ionic drift motion, whereas at high excitation levels they can occur in either direction. The direction of TW oscillations at any level can be controlled or switched, either by means of an external mirror or a weakly resonant loss element which can be tuned to favor either direction. The tendency of the ion ring laser to oscillate in a single direction s attributed in part to the Doppler shift associated with the ion drift velocity, and chiefly to its large natural linewidth. Hole widths burnt in the gain-velocity profile, which are significant in mode competition, usually exceeded the mode spacing of the resonator by large margins. Physical arguments have been advanced to show that, when such large hole widths prevail, and spatial cross-relaxation depends only on ion motions, only running waves can oscillate in a ring resonator, and moreover they will all oscillate in the same direction. Close to threshold, the preferred direction for TW oscillations corresponds to that for which the gain profile is Doppler-shifted to longer wavelengths, possibly because of slightly smaller scattering losses.     

Performance of the Asterix III high power iodine laser

For more than 500 shots the 1 TW iodine laser Asterix III has demonstrated high reliability for light-plasma-interaction experiments. Improved laser parameters and new measurements of light pulse properties are reported.     

超高功率f秒激光器

介绍了 1 0 f秒光脉冲发生器和放大器、 1 0 0 TW低于 2 0 f秒的钛蓝宝石激光器及其应用。