建立聚焦数值模型, 分析少周期径向偏振光聚焦光场的强度以及电场矢量方向周期性变化规律, 对比无啁啾少周期径向偏振光脉冲及连续光束聚焦光场的时空电矢量及强度分布.结果表明, 光强从聚焦光斑中心处向四周迅速减小且振动方向周期性变化; 在相同能量下, 相比于连续光, 脉冲光的聚焦光斑更小, 峰值功率更强; 通过控制光程, 无啁啾少周期径向偏振光束聚焦场的前向电场强于后向电场, 适合于激光电子直接加速.该结果对指导利用少周期径向偏振光进行激光电子直接加速的方案设计及超快显微成像和超快探测具有参考意义.

In order to investigate the detail propertities of the focal spots for the few-cycle radially polarized femtosecond pulses, the numerical focusing modeling was established, and the intensity and vector distribution of the focal electric field were calculated and simulated. The temporal and spatial properties of the focal electric field are included in the modeling. According to the simulation results, the intensity decreases sharply from the focal center, and the oscillation direction changes periodically. Compared with the CW laser beam with the same power, the pulse possesses smaller focusing spot and higher peak power. Furthermore, by controlling the optical length, the synthetic electric fields in the forward direction are of greater ratio than the backward electric fields for a non-chirp few-cycle radially polarized femtosecond pulses beam, which will be favorable for direct laser-induced electron acceleration. The analysis is significant for designing scheme for electron acceleration with the few-cycle radially polarized femtosecond pulses, and also can be a valuable reference for the ultra-fast microscopic imaging and detection.