啁啾超短激光脉冲对二能级体系特性的调控

Modulation of Chirped Ultra-short Pulse on Two-level Atom System

研究了啁啾超短激光脉冲与二能级体系近共振作用下的特性.采用光与物质相互作用的半经典理论,建立了含啁啾相位项的修正光学Bloch方程,并用高准确度、快速和可靠的四阶龙格-库塔法数值求解了该方程.通过数值计算,得到啁啾符号和啁啾量与Bloch矢量的关系,以及共振失谐量符号和啁啾符号对Bloch矢量性质影响的规律.结果表明,啁啾的符号和大小对Bloch矢量的瞬态相干过程和稳态特性都会产生明显的调制作用,由此可以通过调节激光脉冲的啁啾特性来实现对二能级体系性质的调控.

The interactions between a chirped ultra-short pulse and two-level medium on near-resonant were investigated.According to the semi-classical theory of light-matter interaction,the modified Bloch equations with chirped terms were established,and an accurate and efficient fourth-order Runge-Kutta method were applied for solving the equations.After numerical simulation,the relationships between the sign（and value）of chirp and Bloch vectors were obtained,and the influences of signs of detuning and chirp on Bloch vectors were also gained.The numerical results show that,the sign and value of chirp have obvious modulation effects on the transient coherence and steady-state of Bloch vectors,which provides us to control the two-level system by adjusting the pulse chirp.