Femtosecond trapping efficiency enhanced for nano-sized silica spheres

We present a comparison of optical trapping of 50-nm-sized silica nanospheres, suspended in water medium, by femtosecond laser pulses and by continuous wave laser beam. With bright field microscopic imaging, we demonstrated that intensity of scattering light at the focal area under fs-pulse mode is much higher than that under cw mode. This result offers a basic interpretation that trapping efficiency of nanometer-sized particles by the ultrashort laser pulses is higher than that by the cw mode at the same laser power. We interpret this finding by means of impulsive peak power of the femtosecond laser pulses.

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