飞秒激光脉冲推进小球的实验研究

Experimental research of femtosecond laser propulsion of micro beads

利用飞秒激光脉冲分别在水平和竖直方向上进行了推进微型小球的实验。实验中首次利用毫焦量级的飞秒激光脉冲(重复频率1kHz)推进质量在毫克量级的小球,将直径0.7 mm 的铁球水平推进了65 mm,直径接近1 mm 的聚苯乙烯小球竖直推进了72 mm。实验研究发现:无论是在水平还是在竖直方向上的推进,小球离开飞秒激光聚焦区域之前与小球发生作用的脉冲个数是决定推进效果的决定性因素。通过增大脉宽、换用较长焦距的聚焦透镜增加与小球作用的脉冲个数,可以将小球推进到更远的距离或更高的高度。

Micro beads are propelled with continuous femtosecond laser pulses in horizontal and vertical directions respectively.Milli-joule continuous femtosecond laser pulses(repetition rate of 1 kHz)are used to propel milligram micro beads for the first time.In the experiment,iron beads with a diameter of 0.7 mm are propelled to a distance of 65 mm in horizontal direction and polystyrene beads with a diameter of about 1 mm are propelled to a height of 72 mm in vertical direction.From the experiment,we found that for both the horizontal and vertical propulsion the number of laser pulses,which interact with micro bead before the micro bead left the femtosecond laser focal region,determines the final distance or height of propulsion;by using longer pulses and focal lenses with a longer focal length,the number of laser pulses which interact with micro bead can be increased and micro beads can be propelled to a farther distance or a higher level.