电子在超短激光脉冲修正场中的动力学特性研究

Dynamic characteristics of electrons in high-order corrected fields of ultrashort laser pulses

给出了一种精确描述超短、紧聚焦激光脉冲的新方法 ,其思路是根据两个无量纲小量ε =1 (ω0 t0 )和s =1 (k0 w0 ) (其中ω0 =ck0 为中心振荡频率 ,t0 为脉冲延迟时间 ,w0 为激光束腰半径 )进行展开来计算脉冲的高阶修正场 .在激光束近轴近似表达式的基础上 ,给出了高斯脉冲一阶修正场的解析表达式 ,并研究发现其振幅和相位相对于零阶修正场 (即长脉冲近似 )的修正量都在ε的量级甚至更小 .另外对电子在超短高斯脉冲一阶修正场中的动力学特性研究发现 :对于ω0 t0 >2 0的情况 ,零阶修正场可以正确地描述电子被光场加速的特性 ;当ω0 t0 <2 0时 ,则需要采用高阶修正场 .

High-order correction to the fields of ultrashort, tightly-focused laser pulses expressed in power series of epsilon = 1/(omega(0)t(0)) and s = 1/(k(0) omega(0)) (omega(0) = ck(0) the central oscillatory frequency, t(0) the pulse duration, w(0) the beam waist radius), are derived. Based on paraxial approximation, the first-order correction terms to the Gaussian pulses are explicitly given. Their corrections of amplitude and phase, are found to be related to the variable of E. Applying them to the study of the electron dynamics in the intense laser pulse field, we found that as long as w(0) t(0) > 20, the zeroth-order approximation ( long pulse approximation) is adequate for describing the in.teraction. For w(0) t(0) < 20, higher-order corrections have to be taken into account.