共查询到19条相似文献,搜索用时 203 毫秒
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本文综合考虑了在(3+1)维负色散介质中Kerr效应、衍射、色散对光脉冲传输的影响,用变分原理和数值计算的方法对带啁啾高斯光束的传输特性进行了研究,讨论了非线性时空耦合参数,初始束宽、脉宽、散聚特性对时空“自聚焦”特性的影响,计算表明利用会聚光束在负色散克尔介质中传输的耦合作用,可以压缩脉宽,这可作为一种新的压缩脉宽的方法。 相似文献
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啁啾高斯脉冲通过增益色散介质的传输特性 总被引:1,自引:1,他引:0
采用复数波数定义和衍射积分方法,研究了啁啾高斯脉冲在增益色散介质中的传输特性,给出了介质增益谱为洛仑兹分布时的频谱分布以及时空分布的传输解析公式,详细分析了传输过程中光场的频谱和时空分布、脉宽和频谱变化以及谱移等特性。结果表明,啁啾高斯光束在介质中传输时其时间波形仍保持高斯分布不变,但在传输过程中其脉宽会发生变化。在传输过程中,啁啾参量会影响谱宽的减小程度以及谱移的幅度。啁啾参量越大,脉宽展宽和谱宽压窄的效果越明显,同时,随着传输距离的增大,光谱谱移也越明显。对于给定的啁啾参量,随着传输距离的增大,谱移将最终趋于一恒定值。 相似文献
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采用分步法结合Hankel变换对修正薛定谔方程进行数值求解,通过数值计算对飞秒脉冲在非线性正色散介质中的自聚焦特性进行了简要分析。在此基础上,针对啁啾脉冲放大系统(CPA)中的啁啾高斯脉冲,对其全光束自聚焦特性进行了计算模拟和分析讨论。研究结果表明,群速度色散(GVD)对大啁啾脉冲的影响很小,谱宽对自聚集的影响可以忽略。因此,具有大啁啾的脉冲在非线性正色散介质中的自聚焦特性不同于飞秒脉冲,而与纳秒脉冲相似。 相似文献
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Starting from the Rayleigh-Sommerfeld diffraction integral and without invoking the paraxial approximation, analytical expressions for the field distribution, far-field power spectrum and temporal far-field distribution of chirped Gaussian pulses diffracted at a circular aperture are derived, which enables us to study the spectral anomalous behavior of diffracted chirped Gaussian pulses in the far field. The potential applications of spectral anomalies of ultrashort pulses are discussed. It is found that at the critical angle the spectral switch appears. The frequency difference between the two equal heights of spectral switches increases and the corresponding critical diffraction angle slightly increases as the chirp parameter increases and pulse duration decreases. In a certain region of the truncation parameter, the critical angle decreases with increasing truncation parameter. By suitably varying the pulse duration, chirp parameter and truncation parameter, information encoding and transmission are achievable in the use of chirped Gaussian pulses. 相似文献
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对啁啾高斯脉冲光束在色散介质中的时间和光谱特性作了研究.给出了远场光谱蓝移和脉冲展宽的解析式.结果表明:通过选择适当的啁啾参量,啁啾高斯脉冲光束沿轴上传输色散长度时,脉冲可恢复到初始值.随啁啾参量增加,谱线宽度展宽,轴上光谱蓝移增加,在远场蓝移趋于一渐近值.随啁啾参量增加,离轴光谱红移增加. 相似文献
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Xiaoling Ji 《Optics Communications》2008,281(13):3407-3413
The influence of turbulence on the spectrum of diffracted chirped Gaussian pulsed beams is studied in detail. By using the quadratic approximation of the Rytov’s phase structure function and the finite expansion of the aperture function, the analytical expression for the spectrum of diffracted chirped Gaussian pulsed beams propagating through atmospheric turbulence is derived. It is shown that in free space there exist the on-axis and off-axis multi-spectral switch for diffracted chirped Gaussian pulsed beams. However, the turbulence results in a decrease of the spectral transition height, and the spectral switch even disappears when the turbulence is strong enough, which is very different from the behavior of undiffracted chirped Gaussian pulsed beams. Specially, with increasing the strength of turbulence, the higher-order spectral switch disappears firstly for on-axis case, while the lower-order spectral switch disappears firstly for off-axis case. In free space the on-axis spectrum is blue-shifted after a certain propagation distance, but the on-axis spectrum is red-shifted after a shorter propagation distance when the turbulence is strong enough. The spectral transition height increases with increasing the chirp parameter and decreasing the pulse duration, and the odd number order position without spectral shift is independent of the chirp parameter and pulse duration. 相似文献
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超短脉冲高斯光束在线性色散介质中的远场特性 总被引:12,自引:12,他引:0
基于瑞利-索末菲衍射积分公式,在未作近轴近似的条件下,推导出等束宽超短脉冲高斯光束通过线性色散介质的远场公式,并用于研究其远场特性,所得公式可用于大衍射角情况.结果表明,等束宽脉冲高斯光束的频谱上存在一临界角,小于临界角时,出现蓝移;大于临界角时,出现红移,红移量随着衍射角的增大而增大.而脉冲波形将经历时间移动,移动量随衍射角的增大而增大;远场高斯脉冲波形将不再保持不变.此外,群速度色散将引起啁啾,啁啾量随衍射角的增大而减小. 相似文献
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The nonparaxial property of chirped pulsed beam 总被引:1,自引:0,他引:1
The nonparaxial property of the chirped pulsed beam is analyzed both quantitatively and qualitatively. Through the qualitative investigation of the paraxial approximation condition, we show there are chirp-induced changes in the nonparaxial propagation of the chirped pulsed beam. A quantitative nonparaxial correction was developed by use of the perturbational technic and the Fourier transform for a few-cycle chirped pulsed beam with relative small chirp parameter. It was shown that the nonparaxial corrections were enhanced near the leading or trailing edge of pulse depending on weather the chirp parameter is positive or negative. An example for pulsed Gaussian beam driven by a chirped Gaussian pulse is shown in the numerical result to confirm our analysis. 相似文献
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Starting from the space-time Wigner distribution function and taking the Gaussian Schell-model pulsed beam as a typical example, the M2 factor of partially coherent ultrashort pulsed beams is studied. It is shown that the M2 factor increases with increasing bandwidth and decreases with increasing spatial correlation. Furthermore, for chirped pulse, the M2 factor increases as the chirp parameter increases. 相似文献
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Based on the Rayleigh diffraction integral and complex analytical signal representation, the free-space analytical propagation equation and its Fourier spectrum for ultrashort chirped pulsed Gaussian beams with constant diffraction length are derived. The effect of chirp parameter on the spatiotemporal and spectral properties is illustrated with analytical formulas and numerical calculation results. It is shown that the axial spectra of ultrashort chirped pulsed Gaussian beams become broadened with increasing chirp parameter. For single optical cycle, the transversal intensity distribution is affected by increasing chirp parameter, but almost not affected for several optical cycles. Moreover, the positive or negative sign of the chirp parameter has no effect on the spectral distribution and intensity distribution. 相似文献
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Starting from the Huygens–Fresnel diffraction integral and the Fourier transform, the propagation expression of a chirped pulse passing through a hard-edged aperture is derived. Using the obtained expression, the intensity distributions of the pulse with different chirp in the near and far fields are analyzed in detail. Due to the modulation of the aperture, many intensity peaks emerge in the intensity distributions of the chirped pulse in the near field. However, the amplitudes of the intensity peaks decrease on increasing the chirp, which results in the smoothing effect in the intensity distributions. The beam smoothing brought by increasing the chirp is explained physically. Also, it is found that the radius of the intensity distribution of the chirped pulse decreases when the chirp increases in the far field. 相似文献
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给出了超短啁啾洛仑兹脉冲光束在自由空间中的传输方程,研究了啁啾对洛仑兹脉冲光束空间奇异性的影响.理论及数值模拟的结果表明,由于啁啾的作用,对于脉冲宽度大于一个光波振荡周期的洛仑兹脉冲光束同样存在空间奇异性.在初始位置,啁啾洛仑兹脉冲光束的空间奇异性出现在脉冲的前沿或后沿.当洛仑兹脉冲光束传输以后,啁啾洛仑兹脉冲光束的空间奇异性将更加强烈. 相似文献