Simultaneous optical and magnetic manipulation using ferromagnetically doped upconverting particles

Optical tweezers represent a versatile means of trapping and manipulating micro and nano-objects without physical contact, leveraging the unique properties of focused laser beams to exert forces on microparticles. However, optical trapping of traditional metallic and magnetic particles faces challenges due to their large refractive index, absorption characteristics, and plasmonic effects. In response to these challenges, we present Fe-doped upconversion particles. These particles exhibit strong ferromagnetic properties while maintaining adequate refractive index values, making them ideal candidates for opto-magnetic manipulation. Through our work, we demonstrate the simultaneous trapping and magnetic manipulation of these Fe-doped upconverting particles using optical tweezers, enabling precise control over six degrees of freedom of a rigid body, including the three rotational senses. Moreover, we rely on photonic force microscopy to accurately detect the motion of these optically trapped particles exposed to external magnetic fields.