Power spectrum analysis for optical tweezers

摘要: The force exerted by an optical trap on a dielectric bead in fluid is often found fitting Lorentzian to the power spectrum of Brownian motion trap. We present explicit functions experimental that give values parameters fitted, including error bars and correlations, for best such χ2 fit given frequency range. use these determine information content various parts spectrum, find, at odds with lore, much relatively high frequencies. Applying method real data, we obtain perfect fits calibrate tweezers less than 1% when trapping not too strong. Relatively strong traps have spectra cannot be fitted properly any Lorentzian, find. This underscores need better understanding provides. achieved using old new theory incompressible fluid, results ...