Max-Planck Institute for the Science of Light, Guenther-Scharowsky Str. 1/24, D-91058 Erlangen, Germany.
Phys Rev Lett. 2009 Oct 30;103(18):183902. doi: 10.1103/PhysRevLett.103.183902. Epub 2009 Oct 29.
Using a hydrogen-filled hollow-core photonic crystal fiber as a nonlinear optical gas cell, we study amplification of ns-laser pulses by backward rotational Raman scattering. We find that the amplification process has two characteristic stages. Initially, the pulse energy grows and its duration shortens due to gain saturation at the trailing edge of the pulse. This phase is followed by formation of a symmetric pulse with a duration significantly shorter than the phase relaxation time of the Raman transition. Stabilization of the Stokes pulse profile to a solitonlike hyperbolic secant shape occurs as a result of nonlinear amplification at its front edge and nonlinear absorption at its trailing edge (caused by energy conversion back to the pump field), leading to a reshaped pulse envelope that travels at superluminal velocity.
利用充氢空芯光子晶体光纤作为非线性光学气体池，我们研究了 ns 激光脉冲通过反向旋转拉曼散射的放大。我们发现，放大过程具有两个特征阶段。最初，由于脉冲后沿的增益饱和，脉冲能量增加，持续时间缩短。在此之后，形成一个具有比拉曼跃迁相位弛豫时间短得多的持续时间的对称脉冲。由于在其前沿的非线性放大和在其后沿的非线性吸收（由于能量转换回泵浦场），斯托克斯脉冲的轮廓稳定在类孤子双曲正割形状，导致以超光速传播的脉冲包络被重塑。
