新型自脉动多段式分布反馈激光器的理论分析

提出一种新型可产生稳定自脉动光脉冲的多段式分布反馈(MS-DFB)半导体激光器结构,其特点在于各DFB段采用了不同的脊波导宽度.为了对变脊波导宽度MS-DFB激光器的工作特性进行理论分析,利用时域有限差分(FDTD)方法对大信号模型进行了求解.数值计算结果表明,当前、后DFB段脊波导宽度分别为1.5μm和3.0 μm而其他结构参数相同的情况下,MS-DFB激光器可以产生频率为195 GHz的稳定自脉动光脉冲.     

光纤光栅外腔反馈的高功率半导体激光器光谱特性的研究

对光纤光栅外腔反馈的高功率半导体激光器的光谱线宽特性进行了理论与实验研究。理论分析表明，根据不同的外腔参数，激光器的线宽能被压缩或展宽。外腔反射率对光谱线宽的影响要比外腔腔长灵敏得多。实验实现了激光器的线宽由６ｎｍ到０．８ｎｍ的压缩。光纤光栅外腔反馈不仅能改善高功率半导体激光器的光谱特性，而且可提高激光器主模对次模的抑制比。     

Proposal for an All-Optical Flip-Flop Using a Single Distributed Feedback Laser Diode

We introduce a new concept for an all-optical flip-flop based on a single distributed feedback laser. The injection of external light into the laser results in a nonuniform carrier distribution. We will show numerically that this nonlinear effect of the carriers gives rise to a bistability that can be exploited for fast flip-flop operation.     

975nm分布反馈激光器一级光栅的制备

优化设计了975 nm分布反馈激光器的一级布拉格光栅结构.将纳米压印技术与干法刻蚀工艺相结合制备周期为148 nm的光栅结构,通过优化调整刻蚀气体流量比、腔室压强和偏压功率等参数,得到了合适的光栅刻蚀工艺参数.扫描电子显微镜测试显示,光栅周期为148 nm,占空比接近50％,深度合适,表面形貌、连续性和均匀性良好.将所制备光栅应用于975 nm分布反馈激光器中,激光器输出性能良好,波长随温度漂移系数小,光栅对波长的锁定效果良好.     

Design of Balanced Dual‐Band Bandpass Filter with Self‐Feedback Structure

A balanced dual‐band bandpass filter based on λ/2 stepped‐impedance resonators and open‐loop resonators is proposed in this letter. By employing a type of self‐feedback structure, an extra transmission zero is introduced near the common‐mode resonance frequency, and the common‐mode signal is suppressed. The measured results indicate that the filter can operate in 2.46 GHz and 5.6 GHz bands, and the insertion loss is 1.85 dB and 1.9 dB, respectively. Also, better common‐mode suppression is achieved.     

Proposal and Analysis of Distributed Reflector‐Laser Diode Integrated with an Electroabsorption Modulator

A novel integrated laser, that is, a distributed reflector laser diode integrated with an electroabsorption modulator, is proposed to improve the output efficiency, single‐mode stability, and chirp. The proposed laser can be realized using the selective metalorganic vapor phase epitaxy technique (that is, control of the width of the insulating mask), and its fabrication process is almost the same as the conventional electroabsorption modulated laser (EML) process except for the asymmetric coupling coefficient structure along the cavity. For our analysis, an accurate time‐domain transfer‐matrix‐based laser model is developed. Based on this model, we perform steady‐state and large‐signal analyses. The performances of the proposed laser, such as the output power, extinction ratio, and chirp, are compared with those of the EML. Under 10‐Gbps NRZ modulation, we can obtain a 30% higher output power and about 50% lower chirp than the conventional EML. In particular, the simulation results show that the chirp provided by the proposed laser can appear to have a longer wavelength side at the leading edge of the pulse and a shorter wavelength side at the falling edge.     

双波长光纤光栅外腔半导体激光器中波长转换

提出了基于双波长光纤光栅外腔半导体激光器增益饱和效应的全光波长转换方案，特点是可将输入信号同时转换到激光器的2个波长上。在静态波长转换实验中，观察到了1554.8nm输入信号对激光器1531.5nm与1549.4nm波长输出功率的增益饱和作用。表明可实现输入信号到激光器的两个波长的同时转换。     

长腔长体布拉格光栅外腔半导体激光器

为了实现体布拉格光栅外腔半导体激光器(VBL)的外腔腔内光束合成,研究了长腔长VBL的激光输出特性。采用焦距为25 mm的平凸柱透镜作为单管激光二极管(LD)的慢轴准直镜,同时快轴方向体布拉格光栅(VBG)离轴放置,使得VBL的外腔腔长达到约240 mm,线宽从自由运转时的1.8 nm压窄至0.14 nm。在实验中,改变LD的偏振特性,VBL的激光输出特性不变。通过调节VBG温度,该长腔长VBL的激光中心波长从779.18 nm到779.75 nm连续可调,调谐过程中线宽基本不变。     

Feedback Controlled Colloidal Self‐Assembly

Colloidal self‐assembly provides one promising route to fabricate spatially periodic meta‐materials with novel properties important to a number of emerging technologies. However, colloidal assembly is generally initiated via irreversible step‐changes and proceeds along unspecified, non‐equilibrium kinetic pathways with little opportunity to manipulate defects or reconfigure microstructures. Here, a conceptually new approach that enables the use of feedback control to quantitatively and reversibly guide the dynamic evolution of colloid ensembles between disordered fluid and crystalline configurations is demonstrated. The key to this approach is the use of free energy landscape models to inform feedback control laws that close the loop between real‐time sensing (via order parameters) and actuation (via tunable electrical potentials). This approach, which demonstrates controlled assembly to create ordered materials and perform active reconfiguration, is based on chemical physics that suggest it can be generalized to other microscopic processes.     

半导体激光微小振动实时反馈式干涉测量仪

提出了一种带有反馈系统的半导体激光正弦相位调制干涉仪。该干涉仪可以实现对微小振动的高精度实时测量。通过一个简单的信号处理系统对干涉信号进行分析 ,获得实际振动的振幅和频率。由于引入反馈系统 ,减低了测量误差 ,排除了环境噪声的影响。给出了具体的理论分析和实验结果     

Monolithic Integration of a Waveguide Optical Isolator With a Distributed Feedback Laser Diode in the 1.5- μm Wavelength Range

We present first monolithic integration of a waveguide optical isolator with a distributed feedback laser diode (DFB LD) in the 1.5-mum wavelength range. The integrated devices are composed of 0.25-mm-long index-coupled DFB LDs and 0.75-mm-long semiconductor active waveguide optical isolators. The semiconductor active waveguide optical isolators are based on the nonreciprocal loss in the semiconductor optical amplifier (SOA) waveguides with ferromagnetic metals (Fe). The fabrication process consists of two steps of metal-organic vapor phase epitaxy to grow the DFB LD/SOA layer structures, one dry-etching process for the waveguide stripe formation, and three steps of electron-beam evaporation for the electrodes and ferromagnetic metals deposition. They showed single-mode emission at 1543.8nm and 4-dB optical isolation under a magnetic field of 0.1 T.     

Measurement and Characterization of Microwave Interaction between Integrated Distributed Feedback Laser Diode and Electro-Absorption Modulator

Integrated electro-absorption-modulated distributed feedback laser diodes (EMLs) are attracting much interest in optical communications for the advantages of a compact structure, low power consumption, and high-speed modulation. In integrated EML, the microwave interaction between the distributed feedback laser diode (DFB-LD) and the electro-absorption modulator (EAM) has a nonnegligible influence on the modulation performance, especially at the high-frequency region. In this paper, integrated EML was investigated as a three-port network with two electrical inputs and a single optical output, where the scattering matrix of the integrated device was theoretically deduced and experimentally measured. Based on the theoretical model and the measured data, the microwave equivalent circuit model of the integrated device was established, from which the microwave interaction between DFB-LD and EAM was successfully extracted. The results reveal that the microwave interaction within integrated EML contains both the electrical isolation and optical coupling. The electrical isolation is bidirectional while the optical coupling is directional, which aggravates the microwave interaction in the direction from DFB-LD to EAM.     

Dual-Wavelength InAlGaAs–InP Laterally Coupled Distributed Feedback Laser

The design and operation of a novel dual-wavelength laterally coupled (LC) distributed feedback (DFB) semiconductor laser are reported. The laser has two different grating periods, one on each sidewall. Stable dual-mode emission, with low threshold currents and good extinction ratio approaching 30 dB, has been demonstrated. Generation of millimeter-wave signals by photomixing has been performed, and the linewidths of each of the individual modes and of the beat mode have been measured as a function of the injection current. It is observed that while the linewidth of the separate modes has a modest dependence on the injection level, the linewidth of the beat mode experiences a strong decrease as the injected current increases     

Integration of a Rib Waveguide Distributed Feedback Structure into a Light‐Emitting Polymer Field‐Effect Transistor

Ambipolar light‐emitting organic field‐effect transistors (LEFETs) possess the ability to efficiently emit light due to charge recombination in the channel. Since the emission can be made to occur far from the metal electrodes, the LEFET structure has been proposed as a potential architecture for electrically pumped organic lasers. Here, a rib waveguide distributed feedback structure consisting of tantalum pentoxide (Ta₂O₅) integrated within the channel of a top gate/bottom contact LEFET based on poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) (F8BT) is demonstrated. The emitted light is coupled efficiently into the resonant mode of the DFB waveguide when the recombination zone of the LEFET is placed directly above the waveguide ridge. This architecture provides strong mode confinement in two dimensions. Mode simulations are used to optimize the dielectric thickness and gate electrode material. It is shown that electrode absorption losses within the device can be eliminated and that the lasing threshold for optical pumping of the LEFET structure with all electrodes (4.5 µJ cm^?2) is as low as that of reference devices without electrodes. These results enable quantitative judgement of the prospects for realizing an electrically pumped organic laser based on ambipolar LEFETs. The proposed device provides a powerful, low‐loss architecture for integrating high‐performance ambipolar organic semiconductor materials into electrically pumped lasing structures.     

Semiconductor Laser in Distributed Optical Feedback Regime

Wireless Personal Communications - In this work, we first analyse the behaviour of semiconductor laser in the presence of weak-to-moderate feedback from a single (lumped) and double external cavity...     

Maximum and Continuous Wavelength Tuning Ranges of a Grating External—cavity Laser Diode

The wavelength tuning rages of a grating external-cavity laser diode(ECLD)have been studied by the equivalent avity method.The maximum tuning range(MTR)and the continuous tunding range(CTR),which are related to the maximum and the minimum threshold carrier densities,are deduced from the threshold condition.We define a ratio of the CTR to the MRT.This ratio is only determined by the reflectivities of the external and internal facets of the ECLD.The analysis shows that there is an appropriate combination of the external and internalcavity reflectivites to obtain a given CTR in the design of an ECLD.     

用光纤光栅作外反馈的可调谐外腔半导体激光器

制作了一种以光纤光栅作为外反馈的半导体激光器。光纤光栅用紫外曝光法制作 ,反射率为 5 0 %。器件在5 0mA注入电流时 ,出纤功率高于 1mW ,主边模抑制比为 42dB。使用对光纤光栅施加应变和改变光栅温度的方法实现了输出激光波长的调谐 ,利用施加应变方法得到了 2nm范围的输出波长变化。     

混合光栅型的三段式自脉动DFB激光器

制作了1.55μm InGaAsP-InP三段式混合光栅型DFB激光器.观察到了20GHz左右的自脉动信号.讨论了自脉动的产生机制,并且对调相区所起的作用进行了研究.