Exploring the potential of using optically trapped single dust particles as an in-situ plasma diagnostic probe

Current methods of laser manipulation in dusty plasmas primarily focus on manipulating groups of particles suspended in the plasma sheath to explore collective dust-dust interactions. In this study, we have introduced a novel technique known as the universal optical trap (UOT) for trapping and manipulating individual particles in low pressure RF (Radio Frequency) plasmas with or without weak magnetization. The UOT technique has showcased its capability to trap and actively transport single particles of arbitrary properties within plasma. This is achieved by carefully balancing optical, Coulomb, and gravitational forces, using both symmetric and asymmetric optical trapping beam configurations. To observe the stability and motion dynamics of the trapped particles, a real-time imaging system was utilized. Moreover, optical and electromagnetic forces were used to determine charge on a dust particle and electric field in the plasma. Similar measurements were also conducted in a weakly magnetized plasma that was generated by adding a cylindrical bar magnet outside the plasma chamber. We present some results that highlight the potential of using individual particles as in-situ micro-probes for investigating dusty plasmas and magnetized dusty plasmas at a microscopic level.