强吸收石墨微粒在激光作用下的光泳运动研究

Study on Photophoresis of Strong Absorbing Graphite Microparticle Exerted by Laser

以强吸收石墨微粒为研究对象,搭建光镊系统装置,通过实验研究激光作用下空气中石墨微粒的光泳现象。石墨微粒受到激光作用时并未立即发生运动,经历一段时间后,以变加速的形式运动,表明激光对强吸收石墨微粒产生的光泳力远大于辐射压力,可推动石墨运动。但是,激光对强吸收石墨产生光泳力的时间较长,主要取决于石墨的升温速率。受石墨热吸收后温度分布非对称性的影响,光泳力方向不恒定,导致石墨微粒发生变速运动。相同功率作用下,石墨粒径越大,微粒在光泳力作用下的运动速度越小。

The paper presents a self-built experimental setup for studying the photophoresis of airborne strongly absorbing graphite microparticles.Graphite particles did not move immediately when they were exerted by laser,while they moved and rotated at a variable acceleration after a period of time.The results show that the radiation pressure of laser exerting on strongly absorbed graphite particles is small,which is not enough to move the graphite particles.However,the photophoretic force is much larger than the radiation pressure,which can move the graphite particles.Obviously,the time constant of photophoretic force produced by laser on strongly absorbed graphite is higher than that of radiation pressure,which mainly depends on the heating rate.The photophoretic force is affected by the asymmetry of temperature distribution after graphite thermal absorption,and its direction is not constant,which results in the variable speed movement of graphite particles.At the same power,due to photophoretic force,the larger the particle size of graphite is,the smaller translation and rotation speed of graphite will be.