Dresden 2014 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 36: Brownian Motion and Transport

DY 36.2: Talk

Thursday, April 3, 2014, 15:15–15:30, ZEU 160

Resonant Optical Tweezers with Anti-Reflection Coated Titania Microspheres — •Mohammad Kazem Abdosamadi, Anita Jannasch, and Erik Schäffer — Nanomechanics Group, ZMBP - Center for Plant Molecular Biology, University of Tübingen, Auf der Morgenstelle 2, 72076 Tübingen, Germany

Brownian motion is exhibited by an optically tapped particle due to the thermally driven molecules of the surrounding medium. This motion is often considered to be a frequency-independent phenomenon which is known as a white noise process. However, fluid entrainment influences the particle in the trap and results in a frequency-dependent motion. Therefore, the power spectral density (PSD) of the noise that drives the motion is ``colored''. The ``colored noise'' of the Brownian motion can change the behavior of an optical trap from an overdamped oscillator to a resonant one. Here, our goal was to amplify this resonance. Theoretical calculations predict that particles with a large diameter and a high trap stiffness enhance the resonance effect. Therefore, we synthesized large anti-reflection coated titania microspheres. These microspheres have a high trap stiffness in the optical trap. In comparison to our previous work [Jannasch, Phys. Rev. Lett. 2011], the results showed a roughly 4 times enhancement of the resonance in acetone. The resonant behavior could be used as a sensor in analogy to other resonant probes such as an atomic force microscope cantilever.