Towards Stable Trapping of Single Macromolecules in Solution.

The implementation of high instantaneous peak power of a femtosecond laser pulse at moderate time-averaged power (~10 mW) to trap latex nanoparticles, which is otherwise impossible with continuous wave illumination at similar power level, has recently been shown [De, A. K., Roy, D., Dutta, A. and Goswami, D. "Stable optical trapping of latex nanoparticles with ultrashort pulsed illumination", Appd. Opt., 48, G33 (2009)]. However, direct measurement of the instantaneous trapping force/stiffness due to a single pulse has been unsuccessful due to the fleeting existence (~100 fs) of the laser pulse compared with the much slower time scale associated with the available trapping force/stiffness calibration techniques, as discussed in this proceeding article. We also demonstrate trapping of quantum dots having dimension similar to macromolecules.