外光注入半导体激光器实现时钟分频

从理论和实验上研究了利用光注入半导体激光器对高重复速率光脉冲产生的周期振荡和时钟分频现象.结果表明，光注入半导体激光器引起的二倍周期振荡是使注入脉冲重复频率分频的直接原因.通过耦合速率方程，数值模拟了半导体激光器在外光注入时输出光的时间序列和功率谱，并且分析了激光腔内各种周期振荡的特征.研究表明，当注入光使半导体激光器出现稳定的二倍周期振荡，且注入光的重复频率为此振荡频率的二倍时，时钟分频即可产生实验中，采用重复频率为6.32GHz的光脉冲注入Fabry-Perot激光器，实现了3.16GHz时钟分频信号 关键词： 周期振荡 时钟分频 光谱侧带 光注入     

一种新型高速光保持模块

针对光电混合模数转换系统中采样光脉冲很窄,高速积分保持电路实现较困难这一问题,本文提出了一种新型的高速光保持模块.通过使用多个耦合器组成的无源结构,将采样后的超窄光脉冲转换成一族脉冲簇,再经过光电转换和电低通滤波,得到了顶部较平、脉宽较宽的脉冲,有助于降低后续处理电路的复杂度.实验结果表明,这种结构能够较好地实现将超窄脉冲展宽成平顶宽脉冲的功能.     

Nonlinear optical generation and detection of ultrashort electrical pulses in transmission lines

The nonlinear optical generation and detection of subpicosecond electrical pulses on coplanar transmission lines is demonstrated. The electrical pulses are generated by optical rectification of ultrashort optical pulses and detected by electro-optic sampling. Both processes are the result of a second-order nonlinear optical response that occurs in the same poled polymer medium. A bipolar temporal waveform with a FWHM duration of 180 fs for the positive lobe that was measured after a propagation distance of 125 mum was observed. Pulse broadening was minimized by careful attention to the device structure.     

一种新型高速光保持模块

针对光电混合模数转换系统中采样光脉冲很窄,高速积分保持电路实现较困难这一问题,本文提出了一种新型的高速光保持模块.通过使用多个耦合器组成的无源结构,将采样后的超窄光脉冲转换成一族脉冲簇,再经过光电转换和电低通滤波,得到了顶部较平、脉宽较宽的脉冲,有助于降低后续处理电路的复杂度.实验结果表明,这种结构能够较好地实现将超窄脉冲展宽成平顶宽脉冲的功能.     

Electro-optic polymer frequency shifter activated by input optical pulses

We demonstrate electro-optic frequency shifting of 1.55-microm optical pulses by as much as 86 GHz in a polymer traveling-wave phase modulator. The optical pulses were modulated with the linear region of quasi-sinusoidal microwave pulses. In the implemented configuration the electro-optic frequency shifter does not require synchronization with the source of the optical pulses, making it transparent to the optical-pulse repetition rate and increasing its utility. Electro-optic frequency conversion has a number of advantages compared with other methods of all-optical frequency conversion, including no need for a second optical source, high conversion efficiency, and simple control of the output frequency.     

基于光纤环形腔光数据包循环复制的实验研究

通过实验研究了利用不同分光比耦合器构成的光纤环形腔实现光数据包循环复制的效果，并理论分析了影响复制效果的结构因素。耦合器分光比、光纤环形腔中的损耗和噪声对复制效果有不同的影响。光纤环形腔中光放大器、滤波器的加入，以及光脉冲直流基座的降低，可以明显改善输出的幅值和复制序列长度。但实验显示，接近等幅复制的光放大会引起光纤环形腔的自激。在这一情况下，在输出端增加饱和半导体光放大器（SOA）可提高复制信号的识别效果。     

Double optical gating of high-order harmonic generation with carrier-envelope phase stabilized lasers

We demonstrated a novel optical switch to control the high-order harmonic generation process so that single attosecond pulses can be generated with multiple-cycle pulses. The technique combines two powerful optical gating methods: polarization gating and two-color gating. An extreme ultraviolet supercontinuum supporting 130 as was generated with neon gas using 9 fs laser pulses. We discovered a unique dependence of the harmonic spectra on the carrier-envelope phase of the laser fields, which repeats every 2 pi radians.     

Generation of subpicosecond electrical pulses by optical rectification

We describe the generation of subpicosecond electrical pulses by optical rectification of ultrashort optical pulses. The electrical pulses are generated by the second-order nonlinear response of a LiTaO(3) crystal bonded to a coplanar transmission line. A bipolar temporal waveform with a width of 875 fs was measured after a propagation distance of 175mum . This pulse width was limited by the response time of the photoconductive sampler. We observed both broadening and amplitude reduction in the temporal waveform owing to propagation.     

高斯光脉冲在非线性增益介质中的孤子特性

本文从理论上分析了高斯光脉冲在非线性增益介质中的传播特性,从而解释高斯光脉冲的压缩及展宽和形成光孤子的机理。用计算机模拟了不同参数的高斯光脉冲在非线性增益介质中的传播过程,并获得了脉宽沿传播方向变化的定量关系。结果表明,以不同能量向增益介质中注入高斯脉冲,有可能产生各阶光孤子,但由于增益的存在,光孤子的传输距离受到限制。     

Formation and erasure of population difference gratings in the coherent interaction of a resonant medium with extremely short optical pulses

In the regime of coherent interaction of short optical pulses with a resonant medium, which is implemented with a pulse duration shorter than the relaxation times in the medium, the formation of population gratings can occur without overlapping the pulses therein. In this case, there are new possibilities for controlling optical pulses, which are especially pronounced for extremely short pulses. It is shown that, with the proper choice of the parameters of a sequence of extremely short optical pulses, not only the formation of population gratings, but also their erasure are possible. It is demonstrated that this effect can be used for the creation of an ultrahigh-speed optical deflector.     

用于激光聚变驱动器的全光纤、全固化光脉冲产生系统

报道一种全固化、全光纤的用于高功率激光驱动的惯性约束聚变驱动器的光脉冲产生系统,采用单纵模振荡器输出连续激光信号,经过相位调制器和振幅调制器,得到一个时间波形上已整形且具有一定带宽(约0.1 nm)的激光脉冲,经光纤放大器放大并经光纤分束器分束后同时输出四路激光脉冲,各路激光脉冲先通过时间同步调整单元精确控制时间同步关系后,经可编程光纤衰减器调节各路之间的功率平衡后再通过光纤放大器做进一步放大并通过150 m光纤传输输出至预放系统.该光纤系统可输出0.3—20 ns、带宽0.1 nm、能量数纳焦的几乎任意 关键词： 激光聚变驱动器 前端 光纤激光系统     

利用受激布里渊散射在光纤中实现光存储

利用有限差分法在慢变包络近似下求解了耦合波方程组,并从理论上实现了短光脉冲的存储。研究了数据脉冲的读出效率随声子寿命、布里渊增益系数、数据脉冲强度和控制脉冲强度的变化规律。结果显示:在长声子寿命的条件下,可以获得高的读出效率和长的存储时间,而布里渊增益系数和数据脉冲强度对读出效率没有影响;增大布里渊增益系数可以降低所需控制脉冲的强度。这种方法对短脉冲可以实现有效存储,而对长脉冲不能实现存储。     

基于绝热孤子压缩效应的小基座孤子脉冲研究

高重复频率超短光脉冲产生技术是高速光时分复用(OTDM)系统的关键技术之一,而一般的超短脉冲源直接产生的脉冲往往不够窄,因此必须对光脉冲进行压缩后才能满足高速光通信系统的要求。采用360 m长的色散渐减光纤(DDF),成功将从再生锁模光纤激光器(RMLFL)输出的中心波长1546 nm、重复频率10 GHz、脉宽分别为5.40 ps和4.60 ps的光脉冲,绝热压缩为脉宽为1.93 ps和1.71 ps的小基座孤子脉冲,压缩因子分别为2.80和2.69。利用这种绝热孤子压缩方法得到的光脉冲质量较好,可以用于160 Gb/s的光时分复用系统。     

Optical filaments and optical bullets in dispersive nonlinear media

We have investigated the evolution of picosecond and femtosecond optical pulses governed by the amplitude vector equation in the optical and UV domains. We have written this equation in different coordinate frames, namely, in the laboratory frame, the Galilean frame, and the moving-in-time frame and have normalized it for the cases of different and equal transverse and longitudinal sizes of optical pulses or modulated optical waves. For optical pulses with a small transverse size and a large longitudinal size (optical filaments), we obtain the well-known paraxial approximation in all the coordinate frames, while for optical pulses with relatively equal transverse and longitudinal sizes (so-called light bullets), we obtain new non-paraxial nonlinear amplitude equations. In the case of optical fields with low intensity, we have reduced the nonlinear amplitude vector equations governing the light-bullet evolution to the linear amplitude equations. We have solved the linear equations using the method of Fourier transform. An unexpected new result is the relative stability of light bullets and the significant decrease in the diffraction enlargement of light bullets with respect to the case of long pulses in the linear propagation regime.     

用于宽带啁啾脉冲光参量放大系统精确同步的新方法

基于非共线光参量放大,以波长800 nm飞秒激光的倍频光为抽运光,以激光二极管640 nm连续波激光为信号光,产生了与800 nm飞秒激光精确同步的无直流本底的1064 nm脉冲光。实验结果显示该1064 nm的光脉冲在脉冲能量和空间光束质量上均可作为1064 nm波长脉冲放大器的种子光。仅通过一级简单紧凑的非共线参量放大就可实现光周期量级的光参量啁啾脉冲放大系统的抽运激光和种子光的精确同步。     

重复频率可调谐的超低抖动光窄脉冲源的研究

提出了一种新型的基于光电振荡器的重复频率可调谐的超低抖动光窄脉冲源. 光电振荡器系统可以产生超低相位噪声的微波信号; 被该信号调制的直调光经过两次相位调制之后, 使光脉冲的啁啾增强; 再通过一段色散补偿光纤, 光脉冲被进一步压窄. 实验中使用YIG可调滤波器, 可以得到8–12 GHz内步进为200 MHz的可调谐微波信号, 因此光脉冲的重复频率具有可调谐性. 当微波信号即脉冲重复频率为9.6 GHz时, 测得脉冲宽度为3.7 ps, 相位噪声为-130.1 dBc/Hz@10 kHz. 由此得出光脉冲的瞬时抖动为60.1 fs (100 Hz–1 MHz), 因此该方案产生的光窄脉冲源具有超低的抖动.     

A novel time-to-live countdown scheme based on asymmetric Mach-Zehnder interferometer and Fabry-Perot semiconductor optical amplifier

We propose a novel optical time-to-live (TTL) processing scheme using asymmetric Mech-Zehnder interferometer (AMZI) and Fabry-Perot semiconductor optical amplifier (FP-SOA). AMZI transfers M TTL pulses into M - 1 pulses and two residual pulses with 6-dB power difference. FP-SOA enhances the power difference between the M- 1 pulses to the residual pulses to more than 10 dB. A numerical model is established for verifying the feasibility of this scheme.     

Amplification of frequency-modulated soliton-like pulses in inhomogeneous optical waveguides with normal dispersion

The possibility of effective amplification of self-similar frequency-modulated pulses (FMPs) in longitudinally inhomogeneous active optical waveguides is studied. Peculiarities of the dynamics of parabolic pulses with a constant frequency modulation rate are considered. An optimal profile of variation of the group velocity dispersion was obtained in correspondence with optimal amplification of a similariton-like pulse. The use of FMPs in amplifying and longitudinally inhomogeneous optical waveguides with a correspondingly matched profile of normal dispersion of group velocities is shown to be capable of providing for an amplification of subpicosecond pulses up to energies above 1 nJ.     

All-optical pulse shaping for ultrawideband doublet pulses using nonlinear optical loop mirror with optical parametric amplification

We propose and experimentally demonstrate an alternative photonic scheme for the generation of ultrawideband (UWB) doublet pulses, which is based on an optical fiber-based nonlinear optical loop mirror (NOLM) incorporating the optical parametric amplification (OPA) effect. The proposed scheme uses both cross-phase modulation and OPA within an optical fiber-based NOLM to produce an ideal transfer function for the shaping of input soliton pulses into doublet pulses. Using the proposed scheme, a successful conversion of input soliton pulses into doublet pulses is readily demonstrated. The system performance of UWB doublet pulses is also assessed by propagating the 1.25?Gbit/s doublet pulses over a fiber link. Error-free UWB doublet signal transmission is demonstrated.     

Sub-100 fs SDPF optical soliton compressor for diode laser pulses

We report our studies on a fiber-optic soliton compressor for generation of sub-100 femtosecond (fs) optical pulses out of picosecond (ps) diode laser pulses. The soliton compressor is rather simple and composed of a 15 ～ 20 m-long step-like dispersion profiled fiber (SDPF) in conjunction with a single Er-doped fiber amplifier (EDFA). Careful design of such a SDPF compressor was performed, leading to demonstration of 20-fs class compression performance, and experimental investigation was carried out in detail on the optical pulse propagation in the compression processes. In addition, nonlinear fiber loops were applied to suppression of pulse pedestals, resulting successfully in high quality optical pulses of the 100-fs range.