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A nanosecond square pulse fiber laser based on the nonlinear amplifying loop mirror(NALM) is numeri-cally analyzed by the nonlinear Schrdinger equation. The fiber cavity with a NALM has a tendency to provide pulse shaping effect with nonlinearity increasing in the NALM,and the nanosecond square pulse is generated by the pulse shaping effect. The numerical results show that the stable square pulse can be obtained when the parameters of the NALM are chosen appropriately. The generated square pulses have flat top and no internal structure. 相似文献
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建立理论模型,讨论了非线性偏振旋转全光纤锁模激光器的锁模过程、谐波过程以及导致激光器锁模运行难以稳定的影响因素.讨论了采用啁啾脉冲光谱滤波产生脉冲自振幅调制、增加激光器锁模稳定性和自启动能力的机理以及非线性偏振旋转与啁啾脉冲光谱滤波相结合实现锁模的物理过程和脉冲演化过程.研制出全光纤结构的超短脉冲掺Yb~(3+)光纤环形激光器,采用非线性偏振旋转和啁啾脉冲光谱滤波相结合的锁模技术,实现了激光器锁模的开机自启动和高稳定运行.对激光器进行了长期运行稳定性、锁模开机自启动能力、锁模输出参数可重复性监测.锁模脉冲中心波长1052.9 nm,谱宽9.1 nm,脉冲能量4.25 nJ,脉冲宽度17.8 ps.运行期间,各参数波动均小于0.3%.开机自启动能力和可重复性测试显示,激光器可实现一键自启动,启动后各参数可重复精度在0.55%以内. 相似文献
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提出了一种新型的基于高非线性光纤(HNLF)中非线性 偏振旋转(NPR)效应的全光逻辑门实现方案. 将两路非归零码数据信号A和B以及一路直流光同时注入HNLF, 光功率变化导致的非线性双折射在两个偏振分量上引入非线性相对相移, 从而导致光信号的偏振态旋转. 在HNLF输出端, 通过波分解复用器和偏振分束器同时滤出数据信号和直流光的正交偏振态, 从而同时实现多种基础组合逻辑, 并可以在同一段HNLF中实现较为复杂的半加器、半减器逻辑功能. 理论分析了信号光在HNLF中的偏振态演化, 以及利用HNLF中的NPR效应同时实现多种全光逻辑门的原理. 并在实验中得到了10 Gbit/s全光信号"与”、"非”、"或”、"同或”、"异或”、"A· B”、"A·B”、半加器、半减器等逻辑功能, 验证了方案的可行性. 相似文献
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We present the results of the analysis of a fiber laser containing two nonlinear amplifying-loop mirrors (NALM). With the theoretical analysis we have developed, we were able to extend the analysis of a figure of eight laser (F8L) to the case of a similar structure with two NALM. Using the split-step Fourier method we have determined the influence of each NALM coupling ratio on the performance of the laser. We obtain a reduction in the fiber amplifier gain needed to initiate the oscillation as a consequence of this new configuration. Results also show that an optimum combination of the two NALMs' parameters is possible for given optical power and width of the generated pulses. 相似文献
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Govind P Agrawal 《Pramana》1984,22(3-4):293-301
The role of level degeneracy in resonant nonlinear phenomena is examined by considering theJ=1 →J=0 atomic transition. The atomic medium is modelled as a homogeneously broadened three-level system and a closed-form expression
for the medium susceptibility is obtained. It is used to discuss several nonlinear phenomena such as saturated absorption,
optical bistability, and phase conjugation. The two-photon-induced coupling of the ground-state Zeeman sublevels leads to
interesting polarization effects. 相似文献
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Impacts of operational parameters on nonlinear polarization rotation-based passively mode-locked fiber laser
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The operational parameters including the polarization controlling and the pump power in a nonlinear polarization rotation-based passively mode-locked fiber laser are studied in this paper.The carrier rate equations of the activated erbium-doped fiber are first employed together with the nonlinear Shro¨dinger equations to reveal the relation between the operational parameters and the output state of the passively mode-locked fiber laser.The numerical and experimental results demonstrate that the output state of the mode-locked laser varies with the polarization controlling and the pump power.The periodicity of the polarization controlling is observed.With given pump power,there exists a set of polarization controlling under which the ultra-short pulse can be generated.With given polarization controlling,the mode-locked state can be maintained generally except for some particular values of pump power.Three shapes of the output optical spectra from the fiber cavity can be identified when the pump power changes.The results in this paper provide a comprehensive insight into the operation of the nonlinear polarization rotation-based passively mode-locked fiber laser. 相似文献
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Pulse shaping using nonlinear polarization rotation has been analyzed in detail. It is found that there is an optimal, power-dependent polarization ellipticity for the maximum nonlinear transmission. It is also found that the polarization ellipticity should be kept smaller than 0.414 so that higher nonlinear transmission can be obtained. Compared to the well-known scheme of Stolen et al., the peak transmission can be increased more than three times, from 7% to 24%, for an incident power that generates self-phase modulation (φspm) of π. 相似文献
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利用耦合非线性薛定谔方程(CNLSE)为非线性偏振旋转(NPE)锁模自相似光纤激光器建立了一种新的数值模型.模型中,用CNLSE描述脉冲在单模光纤中的传播,在增益光纤中同时考虑了增益带宽和增益饱和作用,用传输矩阵描述构成NPE锁模的光学元件.优化了腔内净色散和光纤长度等参数,模拟了脉冲在激光腔内的演化特性,得到了典型的自相似脉冲运行区域及特点.在最佳自相似脉冲运行区域内,得到了能量约为7 nJ、脉宽约11 ps、线性啁啾的抛物脉冲.比较了不同腔内净色散条件下输出脉冲的特点,给出了三阶色散对输出脉冲的影响.
关键词:
自相似脉冲
非线性偏振旋转锁模
耦合非线性薛定谔方程
数值模拟 相似文献
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Amarendra K. Sarma 《Optics Communications》2011,284(1):186-123
This paper reports a detailed numerical study of soliton switching in a high as well as low birefringent nonlinear coupler. It is shown that by controlling the polarization angle one can have nearly 100% transmission with excellent switching characteristics. It is shown that soliton remains stable during its propagation inside the coupler. However it is observed that high birefringent coupler exhibits relatively better soliton stability. We show that the coupler could be used as a soliton switch even at an input peak power less than the critical power, the power at which 50-50 power sharing takes place between the two cores, just by a judicious choice of the polarization angle. 相似文献
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《中国光学快报(英文版)》2017,(5)
An elliptical initial polarization state is essential for generating mode-locked pulses using the nonlinear polarization rotation technique. In this work, the relationship between the ellipticity ranges capable of maintaining mode-locked operation against different pump power levels is investigated. An increasing pump power, in conjunction with minor adjustments to the polarization controller's quarter waveplate, results in a wider ellipticity range that can accommodate mode-locked operation. Other parameters such as noise, pulsewidth, and average output power are also observed to vary as the ellipticity changes. 相似文献
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Spatial solitons are studied in a planar waveguide filled with nonlinear liquids. Spectral and spatial measurements for different
geometries and input power of the laser beam show the influence of different nonlinear effects as stimulated scatterings on
the soliton propagation and in particular on the beam polarization. The stimulated scattering can be used advantageously to
couple the two polarization components. This effect can lead to multiple applications in optical switching. 相似文献
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The dynamics of a nonlinear optical loop mirror (NOLM) with feedback using a high birefringence fiber in the loop are investigated. The effect of rotating input polarization angle on the output power and polarization angle is numerically examined, illustrating the sensitivity of the NOLM with feedback to the input’s polarization state, as well as the polarization chaos present with sufficient input powers. The inclusion of a polarization-dependant loss in one or both arms of the coupler is also shown to change the output dynamical behaviour of the system. 相似文献
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All-fiber passively mode-locked thulium-doped fiber ring oscillator operated at solitary and noiselike modes 总被引:1,自引:0,他引:1
This Letter presents an all-fiber mode-locked thulium-doped fiber ring oscillator based on nonlinear polarization evolution (NPE). Pumped by an erbium-doped fiber amplified spontaneous emission source, the construction of the laser cavity consisting of only fiber optic components can operate under two different regimes of solitary and noiselike (NL) pulses. Autocorrelation measurements are performed to extract features of these two regimes. 相似文献
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S. A. Pul’kin M. Yu. Savel’eva É. E. Fradkin S. V. Uvarova 《Optics and Spectroscopy》2007,103(6):981-985
Computer simulation of the response (polarization) of three-level systems (for example, of quantum dots) with the common upper level (the Λ-scheme) was carried out for devices of long-term memory with femtosecond driving and signal pulses. For producing an efficient response, the pulse area should be on the order of π. Under the action of the first driving pulse on the 1–2 transition and the simultaneous action of the probe pulse on the 3–2 transition, a long-lived polarization with the lifetime dependent on the lifetimes of the lower (1 and 3) levels appears owing to the nonlinear interference effect. Under the action of the second driving pulse, a signal pulse appears on the 3–2 transition, whose amplitude is proportional to the amplitude of the input probe pulse and exponentially decreases with the delay time between the first and the second driving pulses. The set of equations for the density matrix was solved numerically in the semiclassical approximation and in the rotating wave approximation. The temporal evolution of the nondiagonal matrix elements reflects the temporal evolution of the nonlinear polarization. The polarization spectrum is found by the Fourier transform of the time dependence of the nondiagonal elements. The polarization spectrum (the power spectrum) possesses an interference structure with a fringe period governed by the delay time between the first and the second driving pulses. The inverse Fourier transform reconstructs the temporal shape of the pulses. 相似文献
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In this paper, the results of numerical analysis are demonstrated for sech pulse (soliton) propagation in a birefringent optical fiber using computer modeling and simulation. Here, the initial pulse is polarized linearly and guided into the fiber at an angle of 45° to its polarization axes. The birefringence-induced time delay of 200 and 440 ps between X and Y polarization components has been reported at a fiber length of 631.72 km (10 soliton periods) by considering linear and nonlinear regimes, respectively. The Kerr nonlinearity, which stabilizes solitons against spreading due to GVD, also stabilizes them against splitting due to birefringence. A similar fact is true for the birefringent walk-off. Above a certain soliton order (Nth), the evolution scenario is qualitatively different and two orthogonally polarized components of the soliton move with a common group velocity despite their different modal indices or polarization mode dispersion (PMD) at a fiber length of 631.72 km (10 soliton periods) and 1264.344 km (20 soliton periods) over a nonlinear regime at θ≠45°. The physical effect responsible for this type of behavior is the cross-phase modulation (XPM) between the two polarization components. 相似文献
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An alternative theoretical analysis directed to obtaining a more accurate expression for the critical power in the symmetric nonlinear directional coupler, or other nonlinear, five-layer waveguiding structures, is reported. Our analysis works with the nonlinear supermodes of the waveguide, and it is presented as an improvement of the preceding study by Silberberg and Stegeman [1]. Numerical simulations comparing both techniques, and by means of the beam propagation method, are reported for a few cases. A set of three representative, power dependent parameters is proposed, in order to give a comprehensive view of the power flow between both branches in the device as a function of the excitation conditions. 相似文献
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X. J. Zhu C. H. Wang S. X. Liu G. J. Zhang D. F. Hu C. Y. Zhu J. J. Wang E. X. Fang 《Laser Physics》2011,21(9):1625-1628
A tunable, low-repetition rate, all-normal-dispersion Yb-doped fiber laser (YDFL) that is passively mode locked based on a
phase shifted long period fiber grating (PS-LPFG) is demonstrated and proposed. The mode-locking mechanism of the laser is
based on nonlinear polarization evolution (NPE). Using a PS-LPFG as the spectral filter in the laser cavity, the mode-locked
output wavelength can be tuned continuously and smoothly over a spectral range of 10 nm, which is the first time implementation
of a tunable giant chirped pulse with all-fiber format bandpass filter in YDFL. The maximum output pulse energy is 38.9 nJ
at the repetition rate of 2.499 MHz. 相似文献