| As an emerging field of laser applications,laser propulsion technology has been widely concerned and explored by researchers at home and abroad.Pulsed laser propulsion technology as a kind of laser propulsion,can be considered as the interaction process between the pulsed laser and the target.A high-energy laser pulsed focused on the surface of the target,and breakdown the surrounding medium to generating the high-temperature and high-pressure plasma.Then the plasma expands outward to form the shock wave,which drives the microsphere movement through recoil effect.With the rapid development of the pulsed laser propulsion,numerous research works have gradually shifted from macro field to micro field.However,the traditional propulsion method is that pulsed laser is directly focused through the lens,the laser spot is difficult to control and it is easy to damage the target.In this research,a systematic study on the laser propulsion in the air and water environment is carried out under micro field conditions.The multimode fiber propulsion system and the tapered fiber propulsion system are proposed,which can reduce the damage of the target and directionally propel the microspheres to improve the propulsion efficiency.Combining the experiment with simulation,the influence of variables such as fiber propulsion system,laser energy and bubble on the laser propulsion is analyzed.The specific research content includes:Firstly,an intriguing method of propelling the stainless steel microsphere(～85μm)by employing the nanosecond laser pulses output from the end face of the fiber is demonstrated,in order to investigate the interaction of nanosecond laser pulses with metal microsphere in the air environment.Establishing a two-dimensional model of the shock wave acting on the metal microsphere,and theoretically calculating the propagation characteristics of shock wave.Experimentally,according to the dynamic process,the propulsion efficiency of the microsphere is affected by the fiber propulsion system,laser energy and the distance between the end face of the fiber and the microsphere.In addition,the momentum coupling coefficient and the energy coupling efficiency are calculated to evaluate the laser propulsion efficiency,which resulted in the metal microsphere acquiring a higher momentum and a higher propulsion efficiency.Finally,an experiment is performed to remove the contamination particles on the surface of the microstructure,and eliminate the uncleared blind zone.Secondly,an intriguing method of propelling polystyrene microsphere by employing the nanosecond laser pulses output from the tip of the tapered fiber is demonstrated,in order to investigate the interaction of nanosecond laser pulses with PS microsphere in the water environment.Using the two-dimensional models of the microsphere propelled by the tapered fiber system,the shock wave propagation characteristics have been calculated.Besides,the bubble dynamic process is investigated.Experimentally,the motion image of the microsphere was observed,and the results shown that the propulsion efficiency is dependent on the laser pulse energy.Meanwhile,the high-speed CCD records the dynamic images of the bubble generated from the microsphere,and the bubble diameter monotonously increases with the laser energy and microsphere size.In addition,an experiment is performed to remove the microsphere clusters in the water,which confirms that the tapered propulsion system can be applied in the underwater cleaning field. |
