Size-dependent trapping behavior and optical emission study of NaYF4 nanorods in optical fiber tip tweezers

Trapping of NaYF₄:Er/Yb/Gd nanorods using original optical fiber-tip tweezers is reported. Depending on their length, nanorods are reproducibly trapped in single or dual fiber tip configurations. Short rods of 600 nm length are trapped with two fiber tips facing each other. In contrary, long rods (1.9 µm) can be stably trapped at the apex of one single fiber tip and at a second stable trapping position 5 µm away from the tip. The up-conversion emission of trapped long nanorods is studied as a function of the position on the nanorod and in three orthogonal directions. The experimental results are discussed using numerical simulations based on an exact Maxwell Stress Tensor approach.