Simultaneous detection of two-photon fluorescence and backscatter in laser trapping of dielectric nanoparticles

Devi, Anita; De, Arijit K.

doi:10.1117/1.jnp.13.020501

Cited by 14 publications

(3 citation statements)

References 17 publications

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“…light-induced transformation of the fluorophore into a non-fluorescent photo-product) associated with TPA 17 needs some more attention as it would otherwise lead to erroneous interpretation of data. In fact, TPF detection of optical trapping of 100 nm polystyrene particles under femtosecond pulsed excitation showed rapid decay of TPF signal over time (due to photo-bleaching) although it is much more sensitive in detecting single nano-particle/cluster in a background-free manner 18 . This has motivated us to record and analyze backscatter signal and TPF signal in parallel as they complement each other which we present in this article.…”

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confidence: 99%

Complementing two-photon fluorescence detection with backscatter detection to decipher multiparticle dynamics inside a nonlinear laser trap

Devi

Yadav

2023

Sci Rep

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Using wide-field and point detection modalities, we show how optical trapping dynamics under femtosecond pulsed excitation can be explored by complementing detection of two-photon fluorescence with backscatter. Radial trajectories of trapped particles are mapped from correlated/anti-correlated fluctuations in backscatter pattern whereas temporal evolution of two-photon fluorescence is used to mark the onset of trapping involving multiple particles. Simultaneous confocal detection of backscatter and two-photon fluorescence estimates axial trap stiffness, delineating short-time trapping dynamics. When a second particle is being trapped an oscillatory signal is observed which is due to interference of backscatter amplitudes, revealing inter-particle interactions within the trap. These findings are crucial steps forward to achieve controlled manipulation by harnessing optical nonlinearity under femtosecond pulsed excitation.

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confidence: 99%

Complementing two-photon fluorescence detection with backscatter detection to decipher multiparticle dynamics inside a nonlinear laser trap

Devi

Yadav

2023

Sci Rep

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“…The transmitted white light was imaged onto the CMOS sensor of a camera for video microscopy at a rate of 150 frames-per-second (in 'cropped' mode). The re ected scatter was routed to a confocal aperture (using a 200 µm pinhole and an IR lter) for point detection of back-scatter signal using a PMT, recorded by an automated oscilloscope at 400 µs time interval and the data is plotted after 10-point moving averaging of raw data; however, data analysis is done using the raw data (to exclude artifacts associated with averaging [13]) and trap stiffness values are calculated by averaging over more than 10 sets of data.…”

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confidence: 99%

Deciphering single- and multi-particle trapping dynamics under femtosecond pulsed excitation with simultaneous spatial and temporal resolution

Devi

Yadav

2022

Preprint

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Recent theoretical and experimental studies have shed light on how optical trapping dynamics under femtosecond pulsed excitation are fine-tuned by optical and thermal nonlinearities. Here, we present experimental results of nonlinear optical trapping of single and multiple polystyrene beads (of 1 μm diameter). We show how integration and synchronization of bright-filed video microscopy with confocal detection of backscatter provide both spatial and temporal resolution required to capture intricate details of trapping dynamics. Such spatiotemporal detection is promising to have far-reaching applications in exploring controlled optical trapping and manipulations harnessed by optical and thermal nonlinearities.

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“…Further, the optical trapping of nanoparticles depends critically on the particle material that influences the stability of trapping through the polarizability [10]. Techniques to trap nanoparticles optically thereby involve measures such as nanoparticle design with enhanced polarizability [10], use of plasmonic tweezers/near-field optical trapping [8,9,11,12], or the use of ultrashort laser pulses [13][14][15][16]. Without a deliberate attempt to design for the trapping of nanoparticles, there is a strong possibility that conditions for stable trapping are never satisfied in a conventional OT.…”

Section: Introductionmentioning

confidence: 99%

Trap stiffness modification of an optically trapped microsphere through directed motion of nanoparticles

et al. 2020

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We report an enhancement in the corner frequency of an optically trapped non-magnetic microsphere in the plane perpendicular to the laser propagation direction on addition of ferrofluid to the suspension medium. We conjecture that a directed motion of the nanoparticles toward the trap in this plane is responsible for the augmentation. Changes in the corner frequency in the presence of external magnetic field gradients lend credence to this conjecture. Corner frequency augmentation is also observed when zinc oxide nanoparticles are used. Here, however, no further changes are seen in the presence of magnetic field gradients.

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Simultaneous detection of two-photon fluorescence and backscatter in laser trapping of dielectric nanoparticles

Cited by 14 publications

References 17 publications

Complementing two-photon fluorescence detection with backscatter detection to decipher multiparticle dynamics inside a nonlinear laser trap

Complementing two-photon fluorescence detection with backscatter detection to decipher multiparticle dynamics inside a nonlinear laser trap

Deciphering single- and multi-particle trapping dynamics under femtosecond pulsed excitation with simultaneous spatial and temporal resolution

Trap stiffness modification of an optically trapped microsphere through directed motion of nanoparticles

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