TOAD的开关特性研究

讨论了太赫兹光非对称解复用器 (TOAD)中半导体光放大器 (SOA)对具有不同能量和宽度的控制脉冲的动态增益响应 ,研究了控制脉冲能量、宽度、环时间非对称性、信号光脉冲相对于控制光脉冲的时延等因素对TOAD开关特性的影响 ,作了优化分析 ,并与实验结果进行了比较     

TOAD中半导体光放大器的动态增益响应及光脉冲传输特性研究

讨论了太赫兹光非对称解复用器中半导体光放大器 (SOA)对具有不同能量和脉宽的控制脉冲的动态增益响应 ,研究了不同的逆时针信号脉冲和控制脉冲时延的情况下通过 SOA后的逆时针信号脉冲的功率和相位变化。     

TOAD中半导体光放大器的动态增益响应及光脉冲研究

讨论了太赫兹光非对称解复用器中半导体放大器（ＳＯＡ）对具有不同能量和脉宽的控制脉冲的动态增益响应，研究了不同的逆时针信号脉冲和控制脉冲时延的民政部下通过ＳＯＡ后的地针信号脉冲的功率和相位变化。     

Ultrafast optical packet switching using low optical pulse energiesin a self-synchronization scheme

A detailed numerical treatment is undertaken to investigate the operating characteristics of a self-synchronization scheme based on a modified terahertz optical asymmetric demultiplexer (TOAD) device for ultrafast packet switching. The simulations agree with published experimental measurements. It is shown that input picosecond optical pulse energies as low as ~100 fJ can be utilized to achieve a larger than 10 dB contrast ratio of the first to the remaining pulses of a transmitted signal packet. The utilization of low input pulse energies in the scheme also provides significant advantages including insensitivity of contrast ratio to pulse energies and pulse widths as well as distortionless extracted pulse shapes. Means for achieving a maximum contrast ratio are identified     

An analysis of signal-to-noise ratio and design parameters of aterahertz optical asymmetric demultiplexer

Analysis of the signal-to-noise ratio (SNR) as a function of the component parameters in a terahertz optical asymmetric demultiplexer (TOAD) can help optimize its performance as a demultiplexer or as a router in an optical time division multiplexed network. The analysis presented here accounts for crosstalk due to deviation from a perfect 3 dB splitting ratio in the TOAD's 2×2 coupler, and the degradation of SNR due to fluctuations in the control pulse energy. The spontaneous emission noise output of the semiconductor optical amplifier (SOA) contained in the TOAD is simulated under different degrees of saturation. The analysis indicates that leakage due to the asymmetric placement of the SOA contributes significantly to the crosstalk. To achieve a SNR of 21.5 dB or higher in a 100 Gb/s system, one must use a 2×2 coupler that deviates less than 1% from a perfect 3 dB splitting ratio. Also, control pulse energy fluctuations must be less than 10% for a 20-GHz bandwidth electronic receiver. Novel crosstalk-free designs are proposed and analyzed which meet the stringent requirements of current TOAD devices. A significant enhancement in SNR is predicted when the SOA is operated near the optimal saturation point     

Periodicity Characteristic of TOAD' s Switching Window

The periodicity characteristic of switching window of a terahertz optical asymmetric demultiplexer (TOAD) using numerical simulation was investigated. The results show that the switching window width of TOAD changes periodically with the time asymmetry of TOAD and the period is one half of the period of control pulses. The theoretical results agree with the experimental results very well.     

半导体光放大器的快速饱和效应及其长度对TOAD解复用器性能的影响

分析了半导体光放大器 (SOA)的快速饱和效应及其长度对 TOAD解复用器性能的影响 ,对小开关窗口和大开关窗口两种工作模式进行了研究。经分析发现 ,半导体光放大器的快速增益饱和效应对开关窗口的形状和开关能量都有很大的影响 ,而且开关能量随控制脉冲宽度的变化关系对两种工作模式是完全不同的。研究表明考虑 SOA长度效应后 ,第二个开关窗口的幅度可大大减小 ,这说明适当地增加半导体光放大器的长度可以进一步降低 TOAD的开关窗口 ,提高 TOAD的速率。     

非线性元件的偏移量对TOAD开关窗口的影响

通过数值模拟研究了非线性元件的偏移量对ＴＨｚ光学非对称解复用器开关窗口的影响，结果表明，ＴＨｚ光学非对称解复用器的开关窗口宽度随其时间非对称量作周期性变化，周期为控制脉冲周期的一半。理论计算结果与实验结果完全吻合。从中还发现一个新的窗口可用于数据信号的解复用     

太赫兹光非对称解复用器中自发辐射噪声特性分析

提出了一个在超短脉冲注入半导体光放大器 (SOA)时 ,在考虑了半导体带间效应以及带内效应 ,包括载流子热效应、谱烧孔效应、双光子吸收效应以及超快非线性折射效应的自发辐射噪声的计算模型。并利用该模型计算了放大自发辐射 (ASE)噪声对太赫兹光非对称解复用器 (TOAD)开关性能的影响。数值结果表明 ,在考虑ASE噪声情况下 ,TOAD的开关窗口的边沿更陡 ,在开关窗口的尾部还会出现明显的小峰。结果还表明 ,在输入为理想孤子脉冲下 ,即使考虑ASE噪声 ,在TOAD处于开的状态时 ,其输出信号的信噪比也大于 2 5dB。     

Influence of fast gain depletion on the dynamic response of TOAD's

The operating characteristics of the terahertz optical asymmetric demultiplexer (TOAD) devices subject to picosecond control pulses have been investigated taking into account gain saturation and nonlinear gain compression, due to carrier heating and spectral holeburning. It is shown that when the control pulse width is less than ~2 ps, fast gain depletion process appears in the time resolved gain dynamics of the SOA. The fast depletion process leads to an oscillating output power structure in the switched region. The oscillatory structure is found to persist for over 1 ps and sets a limit on the practical utilization of these devices     

不同脉宽皮秒激光对介质膜损伤修复的热影响

为了更深层次探究超短脉冲激光对惯性约束聚变(ICF)光学系统中常见的多膜层元件损伤修复性能以及特点,分别采用了240、35、6ps的1053nm激光脉冲在1053nm 0°高反膜上进行了损伤修复以及损伤增长测试实验,并在1053nm 45°高反膜上进行了大损伤区域的扫描修复实验。通过比较不同脉宽的修复点形貌以及损伤增长阈值,说明了超短脉冲用于修复多膜层光学元件损伤的优越性,并且脉宽越短修复效果越好。多点脉冲扫描修复结果表明,可以通过三维控制系统来任意控制扫描修复点形貌以达到最佳修复状态。     

光时域反射光纤光栅传感系统中双激光器的驱动设计

为了扩大应变测量的范围,提出了使用两个分布反馈式(DFB)激光器作为光时域反射光纤光栅(OTDR-FBG)传感系统的光源的方法,并设计了相应的纳秒脉冲驱动电路和温控电路,得到两个激光器的驱动脉冲宽度分别为3.10 ns和3.18 ns,脉冲幅值分别为4.40 V和4.08 V,温度控制电路精度达到±0.04 ℃。经测试得到的纳秒脉冲和温控精度满足OTDR-FBG传感系统的要求。     

Self-Q-switched picosecond optical pulse generation with tandem-type AlGaAs TJS laser

Experimental results are presented for ultrashort optical pulse generation by an AlGaAs tandem-type laser with transverse junction stripe structure. The shortest optical pulse width of 14 ps was observed by an ultrafast streak camera, while typical pulse widths were about 20 ps. Further shorter pulses may be expected with this type of semiconductor laser by adequate control of the saturable absorber region.     

Enhanced TOAD performance by negative frequency-detuned signal andcontrol picosecond optical pulses

A numerical investigation has been undertaken of the operating characteristics of Terahertz Optical Asymmetric Demultiplexer (TOAD) devices subject to frequency-detuned signal and control picosecond optical pulses, taking into account the wavelength dependence of the differential gain coefficient and carrier density linewidth enhancement factor. It is shown that, by shifting the signal pulses toward lower frequencies compared with that of control pulses, the contrast ratio can be significantly enhanced and the amplitude modulation can simultaneously be considerably decreased. The switching energy demonstrates small changes over a broad frequency detuning range. The simulations show excellent agreement with published experimental measurements. Furthermore, two operational modes for the TOAD configuration are identified     

Fiber optical parametric amplifier pulse source: theory and experiments

An evaluation of a fiber optical parametric amplifier (FOPA)-based pulse source in terms of pulse width and chirp is presented. Experiments are performed when operating the FOPA as a pulse source, requiring a sinusoidally modulated pump. The FOPA is generating pulses at 10 GHz, and are measured using a streak camera capable of measuring pulses as a function of time, wavelength, and intensity. Experimental results are presented together with a theory for chirp and pulse widths that show good agreement.     

LD泵浦的Cr4+:YAG被动调QNd3+:YAG激光器

从理论和实验两个方面研究了ＬＤ泵浦的Ｃｒ４＋ＹＡＧ被动调ＱＮｄ３＋ＹＡＧ激光器,在考虑激活介质能级精细结构及激活介质有限下能级寿命的情况下,推导了连续泵浦的被动调Ｑ激光器输出脉冲重复率的解析表达式;测量了不同实验条件下的脉冲能量、脉冲宽度和脉冲重复率,并与理论结果进行了比较,理论结果与实验结果大致相符。     

脉冲在增益饱和半导体光放大器中的畸变

分析了半导体光放大器处于增益饱和状态下的自相位调制（SPM）效应对传输脉冲波形、相位的影响，其中着重考虑了不同脉冲指数（高斯脉冲和超高斯脉冲）以及不同脉宽（相对于载流子寿命）的情况。     

Nd: Sr5 (PO4) 3F Crystal Laser Characteristics Using GaAs as Passive Q-switch

It is investigated the properties of a diode-pumped Nd: Sr5 ( PO4 )3F laser that is passively Q-switched by a thin, single crystal GaAs wafer. The short high-peak-power pulses of the laser have been obtained. The pulse energies, pulse widths and pulse repetition rates for different conditions have been measured and the experimental results show that GaAs is an excellent passive Q-switch of the diode-pumped Nd: Sr5(PO4)3F lasers.     

超快激光诱导单晶硅瞬态光学性质演化机理

研究了从亚皮秒到皮秒范围内的不同脉宽和不同能量密度的激光作用下单晶硅材料表面瞬态光学性质的演化规律。这项工作基于考虑了相变潜热的双温方程、载流子数密度模型,通过计算激光辐照过程中的载流子温度、晶格温度和激发态载流子数密度和介电常数,模拟了光子到电子以及电子到声子的能量传递过程,最终得到了单晶硅表面折射率和消光系数的变化结果。有助于揭示亚皮秒到皮秒脉冲宽度范围的超短脉冲激光辐照下,单晶硅材料瞬态光学性质的演化机理。理论结果表明,若单个激光脉冲无法使单晶硅熔化,则不同的激光能量密度和不同的激光脉宽对最小折射率的影响非常有限,在0.3~0.4 J/cm2的激光能量密度范围内,每0.01 J/cm2的能量密度改变引起的最小折射率变化率小于0.5%。若单个激光脉冲能使单晶硅熔化,则不同能量密度和不同脉宽的激光对硅表面的折射率和消光系数有不同程度的影响。该研究结果可为基于超短脉冲激光的单晶硅材料加工和表面改性提供一定的理论指导。     

基于Pulser/Sustainer技术的可调谐长脉冲TE CO2激光器

采用光栅谐振腔,对一台基于Pulser/sustainer技术的紫外预电离长脉冲TE CO2激光器的调谐特性进行了实验研究.在增益体积为1.17 L,激光混合气体体积比V(CO2)∶V(N2)∶V(He)=1∶5∶19,工作气压为30 kPa条件下,实验测量了75条激光谱线的输出脉冲能量和脉冲宽度(半高全宽,FWHM),结果表明,相同的激励条件下,不同的激光波长,激光输出脉冲宽度有所不同.通过仔细观察比较四条主要谱线(9R(20),9P(20),10R(20),10P(20))的激光输出脉冲波形随放电电压、放电脉宽以及气体成分配比等的变化情况,说明基于pulser/sustainer技术激励的长脉冲可调谐TE CO2激光器的激光输出脉冲宽度随调谐波长的不同而变化.简单实验分析表明,谱线增益的变化可能是引起谱线输出脉冲宽度不同的主要原因.