Abstract
An optical bottle method is developed to determine the potential-energy profile of colloidal Rayleigh nanoparticles in an optical trap. The three-dimensional distribution of fluorescent particles in the trap is measured by laser scanning confocal fluorescence microscopy. At sufficiently low concentrations at which interactions between the particles are negligible, the single-particle trapping potential-energy profile is determined from the equilibrium number-density profile by use of the Boltzmann distribution. Fluorescence imaging as well as calculations based on a discrete dipole approximation show that effects due to scattering forces are negligible for polystyrene particles of size less than 10% of the wavelength of the trapping laser, thus justifying the assumption of conservative forces in the equilibrium potential-energy determinations. The new optical bottle method measures the entire two-dimensional trapping-potential profile for an individual nanoparticle without the restriction that only one particle be contained in the trap, thus obviating the need for high laser power.
© 2013 Optical Society of America
Full Article | PDF ArticleMore Like This
Joseph Junio, Jack Ng, Joel A. Cohen, Zhifang Lin, and H. Daniel Ou-Yang
Opt. Lett. 36(8) 1497-1499 (2011)
Yi Hu, Xuanhong Cheng, and H. Daniel Ou-Yang
Biomed. Opt. Express 4(9) 1646-1653 (2013)
Michael P. N. Juniper, Rut Besseling, Dirk G. A. L. Aarts, and Roel P. A. Dullens
Opt. Express 20(27) 28707-28716 (2012)