Spatiotemporal transformation of a focused femtosecond pulse in the absence of self-focusing.
The spatiotemporal transformation of a focused femtosecond pulse in fused silica at power much less than the critical power for self-focusing was numerically studied. We found that the pulse experiences unusual spatiotemporal reshaping, such as refocusing of the near-axis portion of the defocused pulse tail, even when the self-focusing effect was not taken into the calculation. Further studies revealed that a tubelike spatiotemporal distribution of the plasma is formed during pulse propagation and that it plays a decisive role in the transformations of the pulse. In addition, the tubelike plasma was found to exist universally under different external focusing conditions if the input pulse had sufficient power.
State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, China.
Yi
Y
Liu
Hongbing
H
Jiang
Qihuang
Q
Gong