Plasmonic nano-optical trap stiffness measurements and design optimization

Plasmonic nano-optical tweezers offers unprecedented abilities to manipulate nano-objects. However, measuring the trap stiffness at nanoscale dimensions remains a technical challenge, and as a consequence, very few reports have explored plasmonic designs to optimize their trapping performance.

In a recent publication released in Nanoscale, we detail a new approach to measure the trap stiffness taking advantage of the fluorescence emission of the trapped nanoparticle used for calibration. We relate our measurements to numerical simulations, and provide simple rules to optimize the design of the plasmonic structure to improve its trapping performance.

Significance:

- We optimize the design of double nanohole apertures used for plasmonic trapping. Compared to the previous state-of-the-art, our double nanohole structure achieves a 10x higher trap stiffness.

- We detail a general optical method to measure the trap stiffness in virtually any nano-optical tweezers experiment.

- We show that numerical simulations of the peak local intensity inside the structure is a simple and reliable measure to optimize the plasmonic design and the trap performance.

Also freely available on ArXiv.