16 September 2016 Convection currents enhancement of the spring constant in optical tweezers
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In this work we demonstrate the increasing of the trap stiffness (spring constant) constant of an optical trap of particles suspended in water by laser-induced convection currents. These currents are the result of thermal gradients created by a light absorption in a thin layer of hydrogenated amorphous silicon (a:Si-H) deposited at the bottom of cell. Since convection currents (and therefore drag forces) are symmetric around the beam focus particles trapped by the beam are further contained. Around the focus the drag force is directed upwards and partially compensated by radiation pressure depending on the laser power increasing the stiffness of the optical trapping increases significatively so a particle trapped could dragged (by moving the translation stage leaving the beam fixed) at velocities as high as 90μm/s without escaping the trap, whereas with no a:Si-H film, the particle escapes from the trap at lower velocities (30μm/s).
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J. A. Zenteno-Hernández, J. A. Zenteno-Hernández, A. Gómez-Vieyra, A. Gómez-Vieyra, S. A. Torres-Hurtado, S. A. Torres-Hurtado, J. C. Ramirez-San-Juan, J. C. Ramirez-San-Juan, R. Ramos-García, R. Ramos-García, "Convection currents enhancement of the spring constant in optical tweezers", Proc. SPIE 9922, Optical Trapping and Optical Micromanipulation XIII, 99222J (16 September 2016); doi: 10.1117/12.2236243; https://doi.org/10.1117/12.2236243


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