Two particle tracking and detection in a single Gaussian beam optical trap

Applied Optics
P PraveenSharath Ananthamurthy

Abstract

We have studied in detail the situation wherein two microbeads are trapped axially in a single-beam Gaussian intensity profile optical trap. We find that the corner frequency extracted from a power spectral density analysis of intensity fluctuations recorded on a quadrant photodetector (QPD) is dependent on the detection scheme. Using forward- and backscattering detection schemes with single and two laser wavelengths along with computer simulations, we conclude that fluctuations detected in backscattering bear true position information of the bead encountered first in the beam propagation direction. Forward scattering, on the other hand, carries position information of both beads with substantial contribution from the bead encountered first along the beam propagation direction. Mie scattering analysis further reveals that the interference term from the scattering of the two beads contributes significantly to the signal, precluding the ability to resolve the positions of the individual beads in forward scattering. In QPD-based detection schemes, detection through backscattering, thereby, is imperative to track the true displacements of axially trapped microbeads for possible studies on light-mediated interbead interactions.

References

Sep 18, 1989·Physical Review Letters·M M BurnsJ A Golovchenko
Mar 25, 1999·Microscopy Research and Technique·A PralleJ K Hörber
Dec 12, 2001·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·S HendersonP Bartlett
Jan 7, 2003·Physical Review Letters·S A TatarkovaK Dholakia
Aug 17, 1990·Science·M M BurnsJ A Golovchenko
Apr 27, 2012·Optics Express·Frederick B Shipley, Ashley R Carter

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Citations

Jun 17, 2020·Applied Optics·Shruthi Subhash IyengarSarbari Bhattacharya

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