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从描述皮秒光脉冲在色散缓变光纤(FSDD)中所满足的非线性Schro¨dinger方程(NLS)出发,数值模拟了高阶皮秒脉冲在增益系数取值不同的色散缓变光纤中的孤子效应压缩,研究分析了增益系数所产生的影响。计算结果表明,对于孤子阶数确定的光脉冲,增益系数有一最佳取值范围,对应于孤子效应压缩的参量———脉冲压缩比有最佳值。讨论了初始啁啾的影响。 相似文献
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Effects of walk-off on cross-phase modulation induced modulation instability in an optical fibre with high-order dispersion 总被引:1,自引:0,他引:1 下载免费PDF全文
This paper investigates the effects of walk-off among optical pulses
on cross-phase modulation induced modulation instability in the
normal dispersion region of an optical fibre with high-order
dispersion. The results indicate that, in the case of high-order
dispersion, the walk-off effect takes on new characteristics and will
influence considerably the shape, position and especially the number
of the spectral regions of the gain spectra of modulation
instability.
Not only the group-velocity mismatch, but also the difference
of the third-order dispersion of two optical waves will alter the gain
spectra of modulation instability but in different ways. Depending on the
values of the walk-off parameters, the number of the spectral regions may
increase from two to at most four, and the spectral shape and position may
change too. 相似文献
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Cross-phase modulation instability in optical fibres with exponential saturable nonlinearity and high-order dispersion 下载免费PDF全文
Utilizing the linear-stability analysis, this paper
analytically investigates and calculates the condition and gain
spectra of cross-phase modulation instability in optical fibres in
the case of exponential saturable nonlinearity and high-order
dispersion. The results show that, the modulation instability
characteristics here are similar to those of conventional saturable
nonlinearity and Kerr nonlinearity. That is to say, when the
fourth-order dispersion has the same sign as that of the
second-order one, a new gain spectral region called the second one
which is far away from the zero point may appear. The existence of
the exponential saturable nonlinearity will make the spectral width
as well as the peak gain of every spectral region increase with the
input powers before decrease. Namely, for every spectral regime,
this may lead to a unique value of peak gain and spectral width for
two different input powers. In comparison with the case of
conventional saturable nonlinearity, however, when the other
parameters are the same, the variations of the spectral width and
the peak gain with the input powers will be faster in case of
exponential saturable nonlinearity. 相似文献
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高阶色散和指数饱和非线性光纤的调制不稳定性 总被引:1,自引:0,他引:1
采用线性稳定性分析法,解析和计算了指数饱和非线性和高阶色散光纤中的调制不稳定条件和增益谱。结果表明:当二阶和四阶色散同为负时,随着参数的不同,增益谱可能只有一个谱区,也可能出现两个分离的谱区;当二阶和四阶色散分别为正和负时,无调制不稳定性;在其它色散区,则只有一个谱区。指数饱和非线性可能使各谱区的谱宽、峰值增益随入纤功率的增大呈现出先增大后减小的特点,即出现两个不同的输入功率对应同一个不稳定增益峰值和谱宽的情形。在其它参数相同时,指数饱和非线性下增益谱的谱宽和峰值增益随入纤功率的变化速度将比传统饱和非线性更快。 相似文献
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皮秒脉冲在色散缓变光纤中的孤子效应压缩 总被引:11,自引:4,他引:11
本文给出了描述皮秒脉冲在色散缓变单模光纤中孤子效应压缩过程的数学模型。通过数值求解,首次对该孤子效应压缩进行了全面的计算和分析。结果表明,与常规光纤相比,采用色散缓变程度合适的光纤压缩皮秒脉冲,不仅能显著地提高压缩后脉冲的峰值功率和脉冲压缩比,而且能有效地消除压缩后脉冲的次峰和脉座。对于确定的脉冲输入,发现,当光纤的色散缓变程度取某一最佳值时,能获得最佳的压缩效果。进一步研究表明,色散的这一最佳变 相似文献
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The linearized nonlinear propagation equation and its coefficients, gain spectrum of modulation instability (MI) in metamaterials (MMs) with fourth-order linear dispersion, second-order nonlinear dispersion, and three kinds of saturable nonlinearites, are analytically deduced by utilizing the linear stability analysis and Drude electromagnetic model. Then variations of gain spectra of MI with the normalized angular frequencies and the optical power densities are calculated in real units. In the negative refractive region, two kinds of gain spectra are discovered. The first (second) one is close to (far from) the zero perturbation frequencies and it corresponds to the lower (higher) normalized angular frequencies. Moreover, the second one has higher cutoff frequency, which is obviously beneficial to generation of high-repetition-rate pulse trains. While in the positive refractive region, only the first kind of gain spectra is found. With increase of the optical power densities, the peak gains and the spectral widths of MI increase before decrease, but they vary the most rapidly (slowly) for the exponential (conventional) saturable nonlinearities. The MI characteristics and their corresponding applications can be adjusted by several methods. 相似文献
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Periodic solitons are studied in dispersion decreasing fibers with a cosine profile. The variable-coefficient nonlinear Schr¨odinger equation, which can be used to describe the propagation of solitons, is investigated analytically. Analytic soliton solutions for this equation are derived with the Hirota’s bilinear method. Using the soliton solutions, we obtain periodic solitons, and analyze the soliton characteristics. Influences of physical parameters on periodic solitons are discussed. The presented results can be used in optical communication systems and fiber lasers. 相似文献
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Properties of periodic multicrystal configurations in walk-off-compensating second harmonic generation of ultrashort pulses 下载免费PDF全文
This work designs a four-platelet periodic multicrystal configuration in the second harmonic generation of ultra-short pulses as a new walk-off-compensating device. It theoretically investigates a proposed active and a typical passive compensating scheme with the undepleted-pump approximation. The result shows that the angular and spectral band-widths are proportional to the number of crystal pairs as expected,but the temperature tunability is basically unaltered owing to inter-plate pulse interference. At the same time,an analysis reveals that a misuse of the phase mismatch factor is responsible for a historic controversy about pulse interference. A real design of an ultraviolet second harmonic generation (262.5 nm) is considered in a passive periodic β-Barium Borate-calcite configuration,where the inter-plate pulse interference is found to form an azimuthal tuning restriction and to lower plate length tolerance. A subsequent numerical simulation with pump depletion is in good accordance with theoretical prediction. 相似文献
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A time domain dispersion measurement apparatus was successfully built and tested at the Indian Institute of Technology, Madras. This instrument can measure directly the pulse broadening in a multimode optical fibre. The basic dispersion mechanisms in optical fibres and the design details of the system are discussed. 相似文献
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The surface plasmon resonance (SPR) for spectral modulation of the femtosecond laser pulses with 110 nm ultra-broad bandwidth is demonstrated on the basis of the development of ultrashort pulse laser sources which supports good spatial resolution and high peak intensity. Employing the femtosecond surface plasmon polariton pulses launched by a Kretschmann configuration, whose reflectivity curve has the characteristic of the ultra-broad bandwidth, we observe a frequency-dependent loss with greater attenuation at the peak of the spectrum profile than in the wings, which is very useful for adequate spectral modulation. The SPR for the spectral modulation is investigated in theoretical and experimental aspects. The arbitrary spectral modulation of the femtosecond laser pulses can be fulfilled by controlling and optimizing the SPR of the gold film. The experimental result agrees well with the calculation. 相似文献