Suppression of photothermal convection of microparticles in two dimensional nanoplasmonic optical lattice

Photothermalconvection has been a major obstacle for stable particle trapping inplasmonicoptical tweezer at high optical power. Here, we demonstrate a strategy to suppress theplasmonicphotothermalconvection by using vanishingly smallthermal expansion coefficient of water at low temperature. A simple square nanoplasmonic array is illuminated with a loosely Gaussian beam to produce a two dimensionaloptical lattice for trapping of micro particles. We observe stable particle trapping due to near-field optical gradient forces at elevated optical power at low temperature. In contrast, for the same optical power at room temperature, the particles are convected away from the center of theoptical lattice without their accumulation. This technique will greatly increase usable optical power and enhance the trapping capability ofplasmonicoptical tweezer.

Source: Applied Physics Letters - November 18, 2016 Category: Physics Authors: Yi-Chung Chen, Gilad Yossifon and Ya-Tang Yang Source Type: research