Figure 4. (a)–(c) Statistical analysis of the trapped PS as a function of time and laser power for S1-S3 respectively. Solid lines are the exponential fitting to experiment data by using the formula of y = y₀ − A exp (−R₀t) with y₀ and A are constants, R₀ is time coefficient. The inset in (a) shows the schematic of the trapping potential well with a Gaussian profile, whose depth is described as U(r) = −γexp(−r²/a²) where γ is a constant, r is the coordinate, and a is the width of the potential well. (d) Convective drag forces exerted on PS during trapping for S1-S3 respectively. The error bars indicate the experimental standard deviations.