Abstract
In order to investigate optical pulling forces exerted by an electromagnetic field, we develop a theoretical framework based on electrostatic theory and Maxwell stress tensor. We apply this framework to calculate the optical pulling force on elliptical cylinder nanoparticles with gain medium, which we put forward as an alternative material platform to optimize and tailor tractor beams. Moreover, the optical force can be further enhanced and flexibly tuned by controlling the physical and geometrical parameters of the proposed structure. The pulling and pushing force could be switched by changing the location of the hemisphere witch has complex susceptibility in the structure. Altogether, our theoretical findings can pave the way to increase the use of this structure for further applications based on active nanoparticles