Browsing by Author "Pesce, G."

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Open Access
Brownian gyrator: an experimental realization
(OSA, 2017) Soni, Jalpa; Argun, A.; Dabelow, L.; Bo, S.; Eichhorn, R.; Pesce, G.; Volpe, Giovanni
We present an experimental realization of a minimal heat engine in the form of a single Brownian particle, performing gyrating motion by systematic torque generation due to dissipation from two different heat baths in a simple optical tweezer set-up.
Open Access
Long-term influence of fluid inertia on the diffusion of a Brownian particle
(American Physical Society, 2014) Pesce, G.; Volpe, G.; Volpe, G.; Sasso, A.
We experimentally measure the effects of fluid inertia on the diffusion of a Brownian particle at very long time scales. In previous experiments, the use of standard optical tweezers introduced a cutoff in the free diffusion of the particle, which limited the measurement of these effects to times comparable with the relaxation time of the fluid inertia, i.e., a few milliseconds. Here, by using blinking optical tweezers, we detect these inertial effects on time scales several orders longer up to a few seconds. The measured mean square displacement of a freely diffusing Brownian particle in a liquid shows a deviation from the Einstein-Smoluchowsky theory that diverges with time. These results are consistent with a generalized theory that takes into account not only the particle inertia but also the inertia of the surrounding fluid. © 2014 American Physical Society.
Open Access
Quantitative assessment of non-conservative radiation forces in an optical trap
(Institute of Physics Publishing, 2009-05) Pesce, G.; Volpe, Giovanni; De Luca, A. C.; Rusciano, G.; Volpe, G.
The forces acting on an optically trapped particle are usually assumed to be conservative. However, the presence of a non-conservative component has recently been demonstrated. Here, we propose a technique that permits one to quantify the contribution of such a non-conservative component. This is an extension of a standard calibration technique for optical tweezers and, therefore, can easily become a standard test to verify the conservative optical force assumption. Using this technique, we have analyzed optically trapped particles of different size under different trapping conditions. We conclude that the non-conservative effects are effectively negligible and do not affect the standard calibration procedure, unless for extremely low-power trapping, far away from the trapping regimes usually used in experiments.
Open Access
Step-by-step guide to the realization of advanced optical tweezers
(Optical Society of America, 2015-05-05) Pesce, G.; Volpe, G.; Marago, M. O.; Jones, H. P.; Gigan, S.; Sasso, A.; Volpe, G.
ince the pioneering work of Arthur Ashkin, optical tweezers (OT) have become an indispensable tool for contactless manipulation of micro- and nanoparticles. Nowadays OT are employed in a myriad of applications demonstrating their importance. While the basic principle of OT is the use of a strongly focused laser beam to trap and manipulate particles, more complex experimental setups are required to perform novel and challenging experiments. With this article, we provide a detailed step-by-step guide for the construction of advanced optical manipulation systems. First, we explain how to build a single-beam OT on a homemade microscope and how to calibrate it. Improving on this design, we realize a holographic OT, which can manipulate independently multiple particles and generate more sophisticated wavefronts such as Laguerre–Gaussian beams. Finally, we explain how to implement a speckle OT, which permits one to employ random speckle light fields for deterministic optical manipulation.