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首页> 外文学位 >The third-order nonlinear process in femtosecond time-resolved four-wave mixing and femtosecond lasers.
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The third-order nonlinear process in femtosecond time-resolved four-wave mixing and femtosecond lasers.

机译：飞秒时间分辨四波混频和飞秒激光器中的三阶非线性过程。

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摘要

Some basic properties of higher order nonlinear optical processes are examined in this thesis. Two novel applications of third order nonlinear optical processes to device physics are also discussed here. The mechanisms of the nonlinear optical processes were explored, in particular, in four-wave mixing experiments. Applications of the third order nonlinear effect were demonstrated by generation of intense ultrashort pulses in an erbium-doped fiber laser, and also by control of the dynamics of two coupled mode-locked laser oscillators.; Basic properties of higher order nonlinear optical processes were studied in femtosecond time-resolved four-wave mixing experiments. The temporal and spectral properties of the third order, the cascaded third order, and the fifth order nonlinear processes in GaAs were investigated. Both the theoretical and experimental results indicate the cascaded third order process dominates the fifth order process in the regime of band gap resonance, however, the fifth order process dominates the cascaded third order process in the regime removed from the band gap resonance. The destructive interference between the third order and the fifth order processes is also demonstrated clearly in the experiment.; As regards device applications the combined action of a nonlinear optical loop mirror and a nonlinear coupler have been used to mode lock an erbium-doped fiber laser. The laser produces stable pulses trains at 3.8 MHz. The pulses have the duration as short as 1 ps and the peak intensity as high as 2.5 kW. These, to our knowledge, are the most intense pulses generated directly from an erbium-doped fiber laser. At these high intensities, the Raman frequency shift within the laser is not negligible. This significantly influences the transmission of the loop mirror. However, the inefficient transmission of the loop mirror due to the Raman frequency shift can be compensated by the nonlinear phase shift inside the coupler. To induce the nonlinear phase shift inside a coupler, the optical intensity must be much higher than the transmission threshold of the loop mirror.; A pair of colliding pulse mode-locked ring lasers have been coupled by sharing a common saturable absorber. The shared bleaching of the saturable absorber provides an attractive mechanism to synchronize the pulses from two oscillators in time. However, the Kerr lens induced in the shared absorber also provides a repulsive mechanism that tends to separate pulses in time. The relative magnitude of these two opposing mechanisms can be balanced by adjusting the pulse intensity. The experimental work has shown that adjustment of the laser oscillator parameters can result in: pulse synchronization, controllable pulse duration switching, and a bistable state in which the particular pulse that dominates can be determined by prior conditions.
机译：本文研究了高阶非线性光学过程的一些基本性质。本文还讨论了三阶非线性光学过程在设备物理中的两种新颖应用。特别是在四波混频实验中，探讨了非线性光学过程的机理。通过在掺-光纤激光器中产生强烈的超短脉冲，以及通过控制两个耦合锁模激光振荡器的动力学，证明了三阶非线性效应的应用。飞秒时间分辨四波混频实验研究了高阶非线性光学过程的基本性质。研究了GaAs中三阶，级联三阶和五阶非线性过程的时间和光谱特性。理论和实验结果均表明，在带隙共振状态下，级联的三阶过程占主导地位的五阶过程，但是，在从带隙共振中去除的状态下，五阶过程主导了级联的三阶过程。实验还清楚地表明了三阶和五阶过程之间的破坏性干扰。关于装置的应用，已经使用非线性光学环形镜和非线性耦合器的组合作用来锁模掺-光纤激光器。激光在3.8 MHz处产生稳定的脉冲串。脉冲的持续时间短至1 ps，峰值强度高至2.5 kW。据我们所知，这些是直接由掺ped光纤激光器产生的最强脉冲。在这些高强度下，激光器内的拉曼频移不可忽略。这极大地影响了环形镜的透射。但是，由于拉曼频移导致的环形镜传输效率低下，可以通过耦合器内部的非线性相移来补偿。为了引起耦合器内部的非线性相移，光强度必须远高于环形镜的透射阈值。一对碰撞脉冲锁模环形激光器已通过共用一个可饱和吸收器耦合在一起。饱和吸收剂的共享漂白提供了一种有吸引力的机制，可以使两个振荡器的脉冲及时地同步。但是，在共享吸收器中感应的Kerr透镜还提供了一种排斥机制，该机制倾向于在时间上分离脉冲。可以通过调节脉冲强度来平衡这两个相反机制的相对大小。实验工作表明，激光振荡器参数的调整可以导致：脉冲同步，可控制的脉冲持续时间切换以及双稳态，在该双稳态下，可以由先决条件确定占主导地位的特定脉冲。

著录项

  • 作者

    Wu, Song.;

  • 作者单位

    Rensselaer Polytechnic Institute.;

  • 授予单位 Rensselaer Polytechnic Institute.;
  • 学科 Physics Optics.; Physics Condensed Matter.; Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 1993
  • 页码 116 p.
  • 总页数 116
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 光学;无线电电子学、电信技术;
  • 关键词

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