Stochastic Resonant Damping published in Phys. Rev. E

Stochastic resonant damping in a noisy monostable system: Theory and experiment

Stochastic resonant damping in a noisy monostable system: Theory and experiment
Giovanni Volpe, Sandro Perrone, J. Miguel Rubi & Dmitri Petrov
Physical Review E 77(5), 051107 (2008)
DOI: 10.1103/PhysRevE.77.051107

Usually in the presence of a background noise an increased effort put in controlling a system stabilizes its behavior. Rarely it is thought that an increased control of the system can lead to a looser response and, therefore, to a poorer performance. Strikingly there are many systems that show this weird behavior; examples can be drawn form physical, biological, and social systems. Until now no simple and general mechanism underlying such behaviors has been identified. Here we show that such a mechanism, named stochastic resonant damping, can be provided by the interplay between the background noise and the control exerted on the system. We experimentally verify our prediction on a physical model system based on a colloidal particle held in an oscillating optical potential. Our result adds a tool for the study of intrinsically noisy phenomena, joining the many constructive facets of noise identified in the past decades—for example, stochastic resonance, noise-induced activation, and Brownian ratchets.

Surface Plasmon Optical Tweezers published in Phys. Rev. Lett.

Surface plasmon optical tweezers: Tunable optical manipulation in the femtonewton range

Surface plasmon optical tweezers: Tunable optical manipulation in the femtonewton range
Maurizio Righini, Giovanni Volpe, Christian Girard, Dmitri Petrov & Romain Quidant
Physical Review Letters 100(18), 186804 (2008)
DOI: 10.1103/PhysRevLett.100.186804

We present a quantitative analysis of 2D surface plasmon based optical tweezers able to trap microcolloids at a patterned metal surface under low laser intensity. Photonic force microscopy is used to assess the properties of surface plasmon traps, such as confinement and stiffness, revealing stable trapping with forces in the range of a few tens of femtonewtons. We also investigate the specificities of surface plasmon tweezers with respect to conventional 3D tweezers responsible for their selectivity to the trapped specimen’s size. The accurate engineering of the trapping properties through the adjustment of the illumination parameters opens new perspectives in the realization of future optically driven on-a-chip devices.