从索末菲和布里渊先驱到光学先驱
From Sommerfeld and Brillouin forerunners to optical precursors
摘要：
在介质磁化率弱、共振窄的双重极限下，理论上考虑了阶跃调制脉冲在单共振吸收介质中产生的索末菲和布里渊先导。结合直接拉普拉斯-傅立叶积分和计算的鞍点法，我们建立了一个明确的解析表达式的传输场在任何时候都有效，即使当两个先驱显着重叠。我们研究如何他们的完全重叠，发生较短的传播距离，起源形成的独特的瞬态目前命名为共振前兆或动态拍。我们得到的表达，这种瞬态相同的通常在缓慢变化的包络内，尽管初始不连续的入射场包络。本文还简要地讨论了超短脉冲入射产生的动力学拍频和π脉冲
英文摘要：
The Sommerfeld and Brillouin forerunners generated in a single-resonance absorbing medium by an incident step-modulated pulse are theoretically considered in the double limit where the susceptibility of the medium is weak and the resonance is narrow. Combining direct Laplace-Fourier integration and calculations by the saddle-point method, we establish an explicit analytical expression of the transmitted field valid at any time, even when the two forerunners significantly overlap. We examine how their complete overlapping, occurring for shorter propagation distances, originates the formation of the unique transient currently named resonant precursor or dynamical beat. We obtain an expression of this transient identical to that usually derived within the slowly varying envelope in spite of the initial discontinuity of the incident field envelope. The dynamical beats and 0Pi pulses generated by ultra-short incident pulses are also briefly examined
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