Polarization Switching Bistability and Dynamics in Vertical-Cavity Surface-Emitting Laser under Orthogonal Optical Injection

Bistability as well as dynamics associated to polarization switching in a vertical-cavity surface-emitting laser (VCSEL) submitted to orthogonal optical injection from an external master laser are investigated. Intensity-polarization switching bistability is studied by increasing and decreasing the intensity of the injected beam and for a fixed frequency detuning, i.e. the frequency offset between master and the free running VCSEL. Depending on the frequency detuning, bistable switching is experimentally found to occur with or without injection locking of the fundamental mode to the master laser frequency. For large positive detuning, injection locking of the first-order transverse mode with a strong depression of the fundamental mode has been observed. The case of frequency – polarization switching bistability, i.e. when the frequency detuning is first decreased and then increased for a fixed injected power, has also been theoretically analyzed. Qualitative comparison with previous experimental work is presented for the dependence of the width of the bistable switching region on the injection strength level. Finally we show an experimental result of complicated dynamics including period doubling route to chaos that accompany polarization switching and which motivates future theoretical investigations.     

猫眼腔激光器的横模变换与频率分裂

为了产生多种激光横模,以前的系统相对比较复杂,而且一般只能产生基横模和低阶横模,很难产生高阶横模,同时也很难观察到模竞争中一个频率抑制另一个频率的变化过程。基于猫眼谐振腔激光器和频率分裂技术,提出了一种新型的激光原理综合实验系统。该系统利用猫眼逆向器作为He-Ne激光器的一个腔镜,通过调节猫眼逆向器中两镜片间距可输出包括基横模、低阶横模、高阶横模在内的十余种典型横模,并可完成纵模、偏振、出光带宽等多种激光基本特性的实验。同时在基横模状态下,利用谐振腔内加入的石英晶体片可实现激光频率分裂及其频差调节。在此基础上又可实现完整的模竞争过程的观察。     

理论研究电流注入对垂直腔面发射激光器多横模行为的影响

从包含时空变量的速率方程出发,针对弱折射率导引垂直腔面发射激光器(VCSELs),利用空间积分法分析了典型电注入参数对VCSELs多横模行为的影响,在不降低模型准确性的前提下提高了仿真效率。仿真结果表明,注入盘孔径和注入环越小、注入强度越低以及电流扩散越弱时,VCSELs更易实现单横模工作;反之,VCSELs高阶横模开始出现并呈现较强的模式竞争,引发了载流子空间烧孔效应,并导致基模强度降低。进一步得出,在环形注入方式下,高阶模式更容易出现且彼此间的竞争较盘形注入时强。     

弱光反馈下正交时变光注入VCSEL的双稳特性研究

基于垂直腔面发射激光器(VCSEL)的自旋反转模型(SFM),研究了弱光反馈下正交时变光注入VCSEL的双稳特性。研究结果表明,当副激光器(S-VCSEL)受到主激光器(M-VCSEL)正交时变光注入时,弱光反馈的引入不改变正交时变光注入VCSEL的双稳宽度随光注入扫描速率增大而增大的性质;对于确定的光注入扫描速率,随着反馈强度的增大,双稳宽度将变窄;当M-VCSEL与S-VCSEL之间存在频率失谐Δν(等于νm-νs,νm、νs分别为主、副激光器自由运行时的频率)时,随着Δν从负值逐渐增加到正值,双稳宽度总体呈现先减小后增大的趋势,无反馈时在负频区域双稳环宽度呈现的较大波动在引入光反馈后可得到一定程度的抑制。     

Influences of the Current Transverse Profile on the Transverse Mode Competition of VCSELs Diodes

A spatially independent model of vertical-cavity surface-emitting lasers (VCSELs) is derived by integrating the spatially dependent rate equations over the cross section of the cavity of a VCSEL. The angular and radial non-uniformities of the injection current are taken into account. The well-known LP modes of a weakly-guiding cylindrical waveguide are employed to describe the transverse modal structure in the VCSEL cavity. This model is solved in a self-consistent way by using the 4th order Runge-Kutta method. The dependence of transverse mode competition on the current intensity, the angular and radial non-uniformities of the injection current, and the geometrical parameters of the electrical contact are thoroughly investigated and analyzed. The results are useful to the optimum design of the optical transverse modal structure of VCSELs.     

Numerical Investigation of the Effects of the Injection Current on the SHB-Effects of VCSEL''s

A spatially independent model of vertical-cavity surface-emitting lasers (VCSEL's) is built up in this paper by integrating the spatially dependent rate equations over the cross section of the active reigon of VCSEL's. The LP cosine modes in a weakly guiding cylindrical waveguide are used to represent the transverse modes in the VCSEL's cavity. This model is performed numerically with the 4^th order Runge-Kutta method in a self-consistent way. The dynamic and steady state characteristics of the multi-transverse mode competitions are investigated in detail. Different kinds of injection currents such as a disk-contact and ring-contact injection current are employed in these numerically implementations. Some interesting results are obtained and analyzed detailedly.     

相对论核－核碰撞中产生的Λ粒子的横向极化度与横向动量的关联

对在相对论能量下重核反应中产生的粒子的横向极化度进行了测定．对粒子自旋磁矩与磁场相互作用所造成的自旋进动效应进行了修正，得到了粒子的零横向极化度及其与横动量的无关联关系．与较低能量时核－核反应中产生的粒子的极化情况进行了比较．结果表明，在相对论重核反应下的粒子的产生机制有别于高能质子引起的反应和较低能时的核－核反应中产生粒子的机制．     

半导体光放大光纤环形激光器的偏振混沌与相干性

研究了基于半导体光放大器(SOA)的光纤环形激光器的偏振混沌光的特性及其相干性。实验采集激光器的输出功率和偏振度,得到了基于半导体光放大器的光纤环形激光器的输出从自发辐射到受激辐射、再到偏振态混沌激光辐射的演化过程。利用马赫-曾德尔(M-Z)干涉仪验证了混沌激光的相干性,并发现混沌干涉只有零级。测量不同光程差时干涉仪的输出功率,计算相应的干涉条纹可见度,进一步算得混沌激光的相干时间约为40 ps。这一结果与根据光谱计算的该混沌激光的相干时间43 ps基本一致。实验还测得该混沌激光的相干性与半导体光放大器的电流无关。并指出了混沌激光相干应用于低相干光源探测领域的灵敏度和分辨力优势。     

行波半导体光放大器的偏振特性研究

以有源法布里－珀罗谐振腔的增益特性为基础，研究了行波半导体光放大器的偏振特性。对行波半导体光放大器的偏振灵敏度与端面反射率、增益系数、光场限制因子等诸因素之间的关系进行了理论分析和实验研究。在此基础上，讨论了改善行波半导体光放大器偏振灵敏度的若干方法，并提出了新的偏振不灵敏行波半导体光放大器结构。     

光电反馈下光注入VCSELs的动力学特性

基于垂直腔面发射激光器的自旋反转模型,研究了光电负反馈下1 550nm正交偏振光注入垂直腔面发射激光器的非线性动力学特性.研究结果表明:在合适的注入强度和失谐频率条件下,自由运行工作在Y线偏振模式的1 550nm垂直腔面发射激光器可呈现出稳态、稳定注入锁定、单周期、二倍周期、多周期、混沌等多种非线性动力学状态以及偏振转换现象;引入光电负反馈后,1 550nm正交偏振光注入垂直腔面发射激光器将呈现出双频准周期、三频准周期等动力学状态.在注入强度和失谐频率构成的参数空间,反馈延时时间一定时,反馈强度大小对该激光器的动力学状态分布有明显影响;光电反馈强度一定时,在注入强度相对较小的区域,反馈延时时间对该激光器动力学状态分布也有明显影响,而对于注入强度相对较大的区域,该激光器始终工作在单周期或稳定注入锁定态,即反馈延时时间对激光器动态行为的影响较弱.     

Quantum Limits of Polarization Switching in Optical Mesoscopic Devices with Distributively Coupled Quantum Modes

The quantum theory of nonlinear dynamics and the switching effect for two distributively coupled modes in optical systems has been developed based on the Hartree approximation. The quantum limits for observation of the switching effect for the polarization characteristics of light has been determined. The creation of a new type of nonclassical mesoscopic states of light like the Schrödinger-cat states and mesoscopic qubit/qutrit states is predicted. The theoretical prediction is confirmed by a numerical estimation of real systems, i.e., tunnel-coupled optical fibers and waveguides, for the experimental realization of the states under consideration.     

Experimental Injection Map of Semiconductor Laser Submitted to Filtered Feedback

Optical injection consists in the unidirectional coupling between a “slave” laser (SL) and a “Master” laser (ML). The injected SL may exhibit different behaviors, showing frequency locking, wave mixing, relaxation regimes, period doubling, and chaos. The different regimes may be mapped on a chart where the injected power and the detuning between the slave and the master frequencies are varied. In this paper, a detailed overview of the regimes are given when the SL is submitted to both optical injection and filtered optical feedback. This last coupling is realized thanks to an extended cavity, which includes a frequency filter. When the SL is operating far from threshold (4 I_th), typical regimes mentioned for feedback-free laser are observed for all the external-cavity modes. On the contrary, when the SL operates close to threshold (1.5 I_th), it is shown that the dynamics is wealthier. New regimes, as one for which simultaneously chaos and locking occur, can be identified, in comparison to the case of a single-frequency SL.     

利用亚波长矩形金属光栅稳定980nm高功率垂直腔面发射激光器偏振

利用亚波长矩形金属光栅的偏振特性,在垂直腔面发射激光器的有源区引入各向异性增益从而达到控制其偏振的目的.光栅参数设计基于均匀介质理论和抗反射理论,光栅设计周期为186 nm,占空比为0.5,并且光栅制作于GaAs盖层来对TE偏振光提供额外的反射率.经过设计分析对p-DBRs的对数进行了缩减,并且将光栅条之间的盖层区域刻蚀掉,刻蚀深度为1 μm左右.盖层刻蚀的结果使电流注入的方向严格沿着光栅条线性注入的有源区,从而增加了非均匀增益并提高了偏振比.通过多物理场有限元分析软件对器件进行了模拟分析,结果基本上符合设计要求.通过优化工艺步骤,最终得到了550 μm孔径器件的输出功率为780 mW,并且偏振比达到4.8的结果.     

Physical Analysis of a Possibility to Reach the 1.30-μm Emission from the GaAs-Based VCSELs with the InGaAs/GaAs Quantum-Well Active Regions and the Intentionally Detuned Optical Cavities

Physical aspects of an operation of the GaAs-based InGaAs/GaAs quantum-well (QW) VCSELs with the intentionally detuned optical cavities have been considered in the present paper using the comprehensive three-dimensional self-consistent optical–electrical–thermal-gain simulation. In GaAs-based structures, very good DBR resonator mirrors and a very efficient methods to confine radially both the current spreading and the electromagnetic field with the aid of oxide apertures may be applied. It has been found using the above simulation that even currently available immature technology enables manufacturing the above devices emitting radiation of wavelengths over 1.20 μm. In particular, while the room-temperature 1.30-μm lasing emission is still beyond possibilities of the InGaAs/GaAs QW VCSELs, these structures may offer analogous 1.25-μm emission, especially for the high-power and/or high-temperature operation.     

抑制光纤通信系统偏振模色散的措施

偏振模色散(PMD)已成为长距离、高速率光纤通信系统的主要障碍。从光纤的制造工艺、光器件的选择、信号传输三个方面全面分析讨论了偏振模色散的抑制方法,并对这些方法的可行性进行了分析。     

Pulse Self-trapping Robustness to Polarization Mode Dispersion in Optical Fiber

In this paper, pulse self-trapping robustness to polarization mode dispersion in optical fibers is studied. Nonlinear pulse can be used to suppress PMD despite the input pulse shapes is found. When the nonlinear effect is stronger (initial pulse amplitude is larger), the suppression degree to PMD is better. As the initial chirp is considered, we find that the chirp is harmful to suppress PMD. The more is initial chirp, the more is the PMD value.     

Pulse Self-trapping Robustness to Polarization Mode Dispersion in Optical Fiber

In this paper, pulse self-trapping robustness to polarization mode dispersion in optical fibers is studied. Nonlinear pulse can be used to suppress PMD despite the input pulse shapes is found. When the nonlinear effect is stronger (initial pulse amplitude is larger), the suppression degree to PMD is better. As the initial chirp is considered, we find that the chirp is harmful to suppress PMD. The more is initial chirp, the more is the PMD value.     

Light polarization fingerprints on nonlinear dynamics of vertical-cavity surface-emitting lasers

In this paper we summarize the recent results on nonlinear dynamics of vertical-cavity surface-emitting lasers (VCSELs) which are bearing the fingerprints of the particular polarization properties of VCSELs. Due to the surface emission and cylindrical symmetry, VCSELs lack strong polarization anisotropy and may undergo polarization switching and polarization mode-hopping. This provides new specificities to the rich nonlinear dynamics induced in VCSELs by an external perturbation. We unveil both experimentally and theoretically these new specificities for the case of optical feedback, optical injection, and unidirectional synchronization between VCSELs.     

Improvement in Light Output of Thin-Film Vertical-Cavity Surface-Emitting Lasers Transferred onto A1N Substrates

Thin-film 850-nm vertical-cavity surface-emitting lasers (VCSELs) were improved in light output power by designing both the reflectivity of the distributed Bragg reflector on the light-emitting side and also the degree of de-tuning between the photoluminescence peak and the etalon wavelength. Thin-film VCSELs, which were fabricated on A1N substrates by a functional layer transfer technique, are attractive components for the hybrid integration of optoelectronic devices. Their maximum output power was 2.8 mW and their slope efficiency was 0.40 W/A for the 15μm diameter VCSEL devices that we studied. Uniform spontaneous emission over the entire mesa area, and a single transverse laser mode up to 1.3 times the threshold current were confirmed by observing the near-field images.