Interaction between parabolic pulses in a dispersion-decreasing fiber

The properties of the self-similar parabolic pulses interaction in a dispersion-decreasing optical fiber with normal group-velocity dispersion are firstly investigated in our paper. We find that two parabolic pulses separated by a time-delay create oscillation with a sinusoidal fit at the beginning of their overlap, and then further evolve into a train of asymptotic dark solitons. Additionally, outside the overlap regime, the evolution is equal to a single pulse’ propagating behavior. The chirp after interaction in the parabolic pulses still allows for efficient and high-quality pulse compression.     

Generation of excellent self-similar pulses in a dispersion-decreasing fiber

Pulses compression has been widely studied for a long time. In order to generate excellent self-similar pulses in a dispersion-decreasing optical fiber with normal group-velocity dispersion, the influence of initial pulse parameters on the properties of the self-similar parabolic pulses interaction are firstly investigated in the paper. We find that the phase of sinusoidal fit and asymptotic dark soliton change according to the changing of initial phase difference. Meanwhile, increasing the full-width at half-maximum and input energy or decreasing time-delay properly, the interaction between self-similar pulses enhances accordingly, which makes the interaction length shorter and reduce the lose of energy, resulting in high energy output. The results are beneficial in experimental studies by adjusting the initial parameters of pulses to generate high-quality self-similar pulse. It is important for Dense Wavelength Division Multiplexing (DWDM) transmission system which is in heavy demands of light source in wide-range wavelength.     

Timing jitter of solitons compressed in dispersion-decreasing fibers

It is shown that timing jitter owing to the Gordon-Haus (G-H) effect of solitons that are compressed adiabatically in dispersion-decreasing fibers (DDF's) is approximately determined by total dispersion and initial conditions, which are independent of compression dynamics. As a result the established theory for G-H jitter is still applicable. Timing jitter near the levels predicted by theory is observed in pulses from a regeneratively mode-locked fiber laser compressed in a DDF.     

色散缓变掺铒光纤放大器的调制不稳定性

由于掺铒光纤放大器(EDFA)存在增益,相比于传输光纤它有较小的调制不稳定性阈值,使其很容易受到调制不稳定性的影响.本文将用微扰法分析基本的非线性薛定谔方程,研究色散缓变掺铒光纤放大器的调制不稳定性,分析其调制不稳定性积分增益谱与输入信号功率、放大器增益、放大器的长度、光纤纵向色散变化参量的关系.结果显示增大光纤纵向色散变化参量值是减小调制不稳定性对放大器影响的有效途径.通过分析调制不稳定增益产生长度,表明合理的选择放大器的长度可以消除调制不稳定性增益的产生.     

色散渐减光纤中的脉冲展宽研究

讨论了高斯脉冲在五种不同群色散剖面光纤中的传播特性和初始啁啾对脉宽的影响。结果发现:与单模光纤相比,色散渐减光纤(DDF)中的脉冲展宽较慢,并能有效抑制展宽,当β2C>0时,脉冲展宽速度与无啁啾时相比较快,当β2C<0时,脉冲有一初始窄化过程,不同群色散函数对啁啾脉冲有不同的影响。     

Stationary rescaled pulse in dispersion-decreasing fiber for pedestal-free pulse compression

By using the concept of a stationary rescaled pulse (SRP), we analyze an adiabatic soliton compression system based on dispersion-decreasing fiber (DDF). We show that a SRP can exist in a DDF with a linearly decreasing dispersion profile and that the SRP resembles a linearly chirped sech2 pulse. According to the analysis, we show numerically that pedestal-free pulse compression is possible by using the SRP.     

啁啾光脉冲的自相位调制效应对压缩光脉冲的影响

 在超强激光系统中,对比度和本底宽度是压缩光脉冲极为重要的指标。在啁啾脉冲放大系统的压缩阶段,在啁啾脉冲宽度为141ps,啁啾系数为1000,B积分值分别为0,1和2的情况下,模拟了自相位调制效应（SPM）对压缩脉冲的峰值光强、脉冲宽度和本底宽度的影响。结果表明：在B积分值为2的条件下,若不补偿非线性色散,压缩脉冲的峰值强度降为无自相位调制效应时的65%左右,脉冲宽度约为种子脉冲宽度的2倍,本底宽度则增加到原来的3倍左右;在B积分值大于0.5的情况下,本底宽度和B积分值近似成线性关系。     

啁啾光脉冲的自相位调制效应对压缩光脉冲的影响

在超强激光系统中,对比度和本底宽度是压缩光脉冲极为重要的指标。在啁啾脉冲放大系统的压缩阶段,在啁啾脉冲宽度为141ps,啁啾系数为1000,B积分值分别为0,1和2的情况下,模拟了自相位调制效应（SPM）对压缩脉冲的峰值光强、脉冲宽度和本底宽度的影响。结果表明：在B积分值为2的条件下,若不补偿非线性色散,压缩脉冲的峰值强度降为无自相位调制效应时的65%左右,脉冲宽度约为种子脉冲宽度的2倍,本底宽度则增加到原来的3倍左右;在B积分值大于0.5的情况下,本底宽度和B积分值近似成线性关系。     

Parabolic pulse generation in a dispersion-decreasing solid-core photonic bandgap Bragg fiber

We analyze the interplay of nonlinearity and dispersion in a dispersion-decreasing photonic bandgap Bragg fiber as a new platform for generating parabolic pulses. A suitably designed linearly tapered, low-index-contrast, solid-core Bragg fiber - amenable to fabrication by conventional modified chemical vapor deposition technology - is shown to yield stable parabolic pulses. The fiber design was optimized through a simple and accurate transfer-matrix formalism and pulse evolution was studied by the well-known split-step Fourier method. Our study revealed feasibility of generating parabolic pulses in such a dispersion-decreasing Bragg fiber of length as short as 1 m. We have also studied the effect of third order dispersion on generated parabolic pulse, which is an important deteriorating factor in such applications. The effective single-mode operation of the proposed device is achieved through appropriate tailoring of the outer cladding layers.     

54-fs, 10-GHz soliton generation from a polarization-maintaining dispersion-flattened dispersion-decreasing fiber pulse compressor

A 10-GHz train of nearly transform-limited 54-fs soliton pulses was generated by adiabatic compression of the output of a mode-locked fiber laser with a polarization-maintaining dispersion-flattened dispersion-decreasing fiber. The peak-to-pedestal ratio exceeded 23 dB. At high input powers, the pulse width was reduced to as short as 43 fs, although the wings of the pulse were degraded and the jitter increased. The compression properties are different for the two polarization axes, owing to their different dispersion characteristics. The output polarization exhibits no drift.     

Flexible pulses from carbon nanotubes mode-locked fiber laser

We demonstrate a flexible erbium-doped pulsed fiber laser which achieves the wavelength and pulse width tuning by adjusting an intracavity filter. The intracavity filter is flexible to achieve any of the different wavelengths and bandwidths in the tuning range. The wavelength and width of pulse can be tuned in a range of ~ 20 nm and from ~0.8 ps to 87 ps,respectively. The flexible pulsed fiber laser can be accurately controlled, which is insensitive to environmental disturbance.     

Parabolic pulse generation by use of a dispersion-decreasing fiber with normal group-velocity dispersion

We propose a new method for generating a parabolic pulse by use of a dispersion-decreasing fiber with normal group-velocity dispersion. When a hyperbolic dispersion-decreasing structure is employed, the pulse evolves into a linearly chirped pulse with an exact parabolic intensity profile without radiating dispersive waves. The highly linear chirp in the parabolic pulse allows for efficient and high-quality pulse compression.     

Single-shot dynamics of pulses from a gas-filled hollow fiber

We present measurements of the performance characteristics of few-cycle laser pulses generated by propagation through a gas-filled hollow fiber. The pulses going into the fiber and the compressed pulses after the fiber were simultaneously fully characterized shot-by-shot by using two kHz SPIDER setups and kHz pulse energy measurements. Output-pulse properties were found to be exceptionally stable and pulse characteristics relevant for non-linear applications like high-harmonic generation are discussed. PACS 42.65.Re; 42.65.Ky; 42.65.Sf; 42.65.Jx     

Distortion of parabolic pulse due to higher-order effects in a dispersion-decreasing fiber

Considering Third-order Dispersion (TOD) and Stimulated Raman Scattering effect (SRS) simultaneously, the properties of the self-similar parabolic pulse evolution in a dispersion-decreasing optical fiber with normal group-velocity dispersion are firstly investigated in our paper. Our results show that parabolic pulses are distorted and the characteristic of exactly self-similarity will be lost due to the High-order effects. When only the TOD is taken into account, the chirp still reveals highly linear but glows into asymmetric which causes the waveform appearing optical wave breaking. When only considering SRS, the pulse still reveals highly linear chirp only linearity range narrow down, resulting in delaying the self-similar evolution. When considering SRS and TOD simultaneously, parabolic pulses are distorted less and the characteristic of exactly self-similarity will be better due to SRS effect than only considering TOD effect. The highly linear chirp in optical pulse still allows for efficient and high-quality pulse compression by use of dispersion compensation technique.     

Experimental demonstration of similariton pulse compression in a comblike dispersion-decreasing fiber amplifier

Self-similar propagation of linearly chirped hyperbolic-secant pulses in a comblike decreasing-dispersion fiber amplifier has been observed experimentally for the first time to our knowledge. The scheme takes advantage of an exact solution of the generalized nonlinear Schr?dinger equation with distributed coefficients.     

Dual-wavelength stable nanosecond pulses generation from cladding-pumped fiber laser

In this paper, the generation of dual-wavelength stable nanosecond pulses by a laser diode pumped Ybdoped double-clad fiber laser is presented. In the experiment, the fiber laser with two-mirror cavity is approved which operates in a self-Q-switching regime. The Q-switching mechanism is based on stimulatedBrillouin scattering (SBS). When the pump power achieves the SBS threshold, the fiber laser changes from the start resonator to the SBS resonator. With different reflectivities of the second mirror, stable dual-wavelength pulses with the pulse width range from 10 ns to less than 2 ns are obtained. The resultwas explained theoretically by birefringency (including stochastic birefringency and bend birefringency).     

Stimulated Brillouin scattering in dispersion-decreasing fiber with ultrahigh-speed femtosecond soliton pulse compression

We report that stimulated Brillouin scattering (SBS) in a dispersion-decreasing fiber (DDF) is particularly disadvantageous with ultrahigh-speed femtosecond soliton compression that exceeds 40 GHz. It is important to note that the increase in the longitudinal mode power of a soliton is proportional to the square of the repetition rate. The SBS threshold is determined by the dispersion-decreasing rate of the DDF, rather than its fiber loss. We suppressed the SBS by applying 30-MHz frequency modulation to a mode-locked fiber laser and successfully obtained a stable 40-GHz, 100-fs pulse train.     

Dual-frequency pulses in fiber lasers

We analyze pulse propagation in a soliton fiber laser, modelled by the complex Schrödinger-Ginzburg-Landau equation. It is shown that this equation admits two previously unknown forms of stable stationary solutions. The first of them is a dual-frequency pulse, which propagates as a single unit, but has two symmetric peaks in the spectrum. The second one is a moving pulse, with the asymmetric double-hump spectrum.     

泵浦光波形和脉宽对飞秒激光对比度的影响

 采用宽带数值模型，应用四阶龙格-库塔数值算法对三波耦合方程进行数值分析，研究了泵浦光的波形和脉宽在提高光参量啁啾脉冲放大系统输出飞秒激光对比度的作用。结果表明：在泵浦光脉宽较小的条件下，采用平滑的泵浦光波形更有利于提高飞秒激光对比度；在泵浦光脉宽较宽时，飞秒激光对比度得到很好地提高，而对泵浦光波形不敏感；但继续提高泵浦光脉宽并不能进一步改善飞秒激光对比度，而系统的转换效率却显著降低。     

泵浦光波形和脉宽对飞秒激光对比度的影响

采用宽带数值模型,应用四阶龙格-库塔数值算法对三波耦合方程进行数值分析,研究了泵浦光的波形和脉宽在提高光参量啁啾脉冲放大系统输出飞秒激光对比度的作用。结果表明：在泵浦光脉宽较小的条件下,采用平滑的泵浦光波形更有利于提高飞秒激光对比度;在泵浦光脉宽较宽时,飞秒激光对比度得到很好地提高,而对泵浦光波形不敏感;但继续提高泵浦光脉宽并不能进一步改善飞秒激光对比度,而系统的转换效率却显著降低。