亚稳态氦原子束在激光驻波场中聚焦的衍射像差研究

Diffraction Aberration of Focusing Atom Beam of Metastable Helium in Laser Standing Wave

用量子力学方法研究了一维激光驻波场对亚稳态氦原子束聚焦的衍射像差。建立了半经典模型 ,该模型在一定条件下和已有模型一致 ,提出了直接计算时间演化算符的数值方法 ,这种计算方法速度较快 ,收敛性较好 ,数值模拟结果表明在一定的激光强度和光束半径等参量下 ,亚稳态氦原子束被聚焦 ,焦点的半峰全宽为 54nm ,对比度 1 6∶1 ,焦长、焦深与入射原子束的速度有关 ,从而与动能有关 ,焦点的有限宽度主要是来自衍射效应的影响。

The diffraction aberration of focusing atom beam of metastable helium in laser standing wave is studied by using quantum mechanics. A quasi classical model accordance with the existing model under the particular condition is built. The time dependent evolution operator method with fast computational speed and convergence is put forward to perform the calculations. Under given parameters of laser power and diameter etc, the simulation resnlts show that atom beam of metastable helium has been focused with a FWHM of 54 nm and contrast of 16∶1, the focal length and focal depth related to velocity and energy of atom beam. The diffraction effect contribute to the limited width of focus mostly.