Mechanism And Experimental Study Of Microspheres Driven By Nanosecond Pulse Laser Emitted From Optical Fiber

As an advance propulsion concept,pulse laser propulsion has attracted wide attention because it can be widely used in various fields.Compared with traditional chemical propulsion,pulse laser propulsion has the advantages of large specific impulse and high load ratio.Besides,it is safe and environmentally friendly in the process of propulsion.Pulse laser propulsion technology has important application value in the fields of microsatellite launch,satellite attitude adjustment,orbital debris removal and laser cleaning of contamination particles.In addition,with the continuous development of science and technology,the requirements for the integration and miniaturization of electronic devices are expanding.The research has gradually shifted from the macro to the micro field.When the laser is focused directly through the lens,the target may be damaged due to the large spot diameter and high energy.Meanwhile,the adjustment of spatial light path is not flexible enough to drive micro scale targets.This thesis mainly uses the method of fiber coupled pulse laser to drive the microspheres,which can effectively reduce the spot diameter and decrease the laser energy on the microsphere.In addition,optical fiber which has good flexibility can operate the laser propulsion of micro-nano target flexibly.Firstly,high speed photography and spectral analysis methods were used to confirm the formation of air plasma at the fiber end.The laser-induced plasma shape and characteristic parameters are analyzed by change the laser energy.In addition,the propagation characteristics of the plasma shock wave are analyzed by theoretical simulation,including the relation between the velocity and propagation time.Meanwhile,the variation law of the pressure and intensity of the shock wave with the laser energy was analyzed theoretically.Then,the interaction of shock wave with the SS microspheres was investigated to observe the effect of energy density on microspheres motion.The results show that there is a strong correlation between the propulsive efficiency and the energy density.The propulsion efficiency of stainless steel and polystyrene microspheres was observed by changing the energy density.Different laser energy deposition results in different propulsive efficiency of the microspheres.In comparison,the propulsive efficiency of metallic microspheres is higher than polystyrene microspheres.Meanwhile,the influence of the distance between the fiber end and the microsphere on the force was experimentally studied.The results show that the force on the microsphere decreases monotonously with the distance when the energy is constant.In addition,the motion modes of the microsphere were analyzed,including sliding,rolling and lift modes.