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Tuesday, August 4, 2015

A Simplified Configuration for Obtaining a Variable Focal Spot for Optical Tweezers

Yanghui Li, Zhaoyi Shi, Le Wang

We propose a simplified setup to generate a tunable focal spot. To make a flexible conversion between a doughnut focal spot and a peak-centered one, we introduce a dual ramp phase mask and realize the focal spot manipulation by changing the modulation coefficient. In this way, this configuration enables the trapping and controlling of the particles with diverse refractive index. Further we present an analysis of the system performance and investigate explicitly some key aspects that may affect the quality of the focal spot generated, including the polarization purity and the accuracy of the phase modulation.

DOI

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