Optical lock-in particle tracking in optical tweezers

TL;DR

This paper introduces a lock-in particle tracking method in optical tweezers using stroboscopic modulation, significantly reducing low frequency noise and enhancing measurement precision.

Contribution

A novel lock-in tracking scheme that suppresses low frequency noise in optical tweezers, compatible with existing setups and demonstrating substantial noise reduction.

Findings

Achieved 20dB noise suppression at 10-5000 Hz

Achieved 35dB noise suppression at 550-710 kHz

Compatible with standard optical trapping systems

Abstract

We demonstrate a lock-in particle tracking scheme in optical tweezers based on stroboscopic modulation of an illuminating optical field. This scheme is found to evade low frequency noise sources while otherwise producing an equivalent position measurement to continuous measurement. This was demonstrated, and found to yield on average 20dB of noise suppression in the frequency range 10-5000 Hz, where low frequency laser noise and electronic noise was significant, and 35 dB of noise suppression in the range 550-710 kHz where laser relaxation oscillations introduced laser noise. The setup is simple, and compatible with any trapping optics.