Comparing Femtosecond Optical Tweezers with Conventional CW Optical Tweezers

TL;DR

This study compares the effectiveness of femtosecond pulsed optical tweezers with conventional continuous-wave ones across various particle sizes and laser powers, revealing pulsed tweezers' superior trapping stability especially for smaller particles at higher powers.

Contribution

It provides a direct experimental comparison between pulsed and CW optical tweezers under identical conditions, highlighting the advantages of pulsed trapping for small particles.

Findings

Pulsed tweezers are more effective for trapping smaller particles.

At higher powers, pulsed tweezers offer more stable trapping.

Both methods are similarly effective for larger particles at lower powers.

Abstract

In this work, we present a comparative study between continuous-wave (CW) and pulsed optical tweezers for 250 nm, 500 nm and 1-micron radius polystyrene beads at 5 different laser powers. We have used a Ti:Sapphire (MIRA 900F) laser that can be easily switched from CW to pulsed mode of operation, so there is no change in the experimental conditions in the two cases. We have measured the difference in the trap strength in both cases by fitting the power spectrum curve with Lorentzian. As it turns out, trapping with pulsed tweezers seems to be more effective for the smaller particles and as the particle size is increased both CW and pulsed tweezers appear to be equally effective at lower average laser powers but as the power is increased pulsed tweezers do a better job at stable trapping.