CAJ | 학술논문

利用不含慢变包络近似和旋波近似的全波Maxwell-Bloch方程组的数值解,研究了周期量级超短激光脉冲在Ladder型三能级原子介质中的传播行为并与在相应的稀疏介质中的情况进行了比较.我们发现,在传播过程中,超短脉冲在稠密介质中的时间演化规律与在稀疏介质中明显不同,而且这种差别将随初始脉冲面积的增大而加大.当初始脉冲面积较小时,在传播过程中,脉冲形状在稀疏介质中只有小的改变而在稠密介质中却有显著的变化.当初始脉冲面积足够大时,在稠密介质中在不同的传播距离处脉冲分裂为不同数量和形状的亚脉冲;在稀疏介质中脉冲形状在传播过程中仍然只有小的改变.产生以上差别的原因在于稠密原子介质中近偶极-偶极(NDD)相互作用导致的局域场修正(LFC) 及比稀疏原子介质更强的极化电场的影响.其中,更强的极化电场的影响起着主要的作用,但局域场修正的作用也不能忽略,而极化电场的增强是由于原子密度的增加.
이용불함만변포락근사화선파근사적전파Maxwell-Bloch방정조적수치해,연구료주기량급초단격광맥충재Ladder형삼능급원자개질중적전파행위병여재상응적희소개질중적정황진행료비교.아문발현,재전파과정중,초단맥충재주밀개질중적시간연화규률여재희소개질중명현불동,이차저충차별장수초시맥충면적적증대이가대.당초시맥충면적교소시,재전파과정중,맥충형상재희소개질중지유소적개변이재주밀개질중각유현저적변화.당초시맥충면적족구대시,재주밀개질중재불동적전파거리처맥충분렬위불동수량화형상적아맥충;재희소개질중맥충형상재전파과정중잉연지유소적개변.산생이상차별적원인재우주밀원자개질중근우겁-우겁(NDD)상호작용도치적국역장수정(LFC) 급비희소원자개질경강적겁화전장적영향.기중,경강적겁화전장적영향기착주요적작용,단국역장수정적작용야불능홀략,이겁화전장적증강시유우원자밀도적증가.
Using the numerical solution of the full Maxwell-Bloch equations without the slowly varying envelope approximation and the rotating-wave approximation, propagation behavior of few-cycle laser pulse in a dense ladder-type three-level atomic medium is investigated and it is compared with the case in the corresponding dilute medium. It is found that, in the propagation process, time evolution of the pulse in the dense medium is obviously different from that in the dilute medium, and the difference will become more evident with increasing of the initial pulse area. When the initial pulse area is smaller, in the propagating process, the pulse shape in the dilute medium just have a small change; the pulse shape in the dense medium has considerable variation but the pulse splitting doesn't occur. When the initial pulse area is larger enough, for the dense medium case, the pulse splits into sub-pulses with different numbers and shapes at different propagation distances; while for the dilute medium case, variation of the pulse shape is still smaller in propagation process. The cause producing above difference is from two effects in the dense medium: the effect of the local-field correction (LFC) from the near dipole-dipole interaction and effect of stronger polarization field than that in the dilute medium. In which the effect of stronger polarization field plays a main role, but the role of LFC also cannot be neglected,and the stronger polarization field is due to the atomic density increasing .