Manipulation of optically levitated particles

Isaksson, Oscar; Karlsteen, M.; Rostedt, Mats; Hanstorp, Dag

doi:10.1117/12.2023860

“…In the context of our experiment, which concerns the collision process of binary droplets in a gravitational field, the presence of charge may add complexity but is not at all unfavorable. Possible diagnostic measures to determine the amount of electrical charge on individual droplets include applying a DC or AC electric field across the droplet and measuring the displacement from its equilibrium position [27].…”

Section: Electrical Chargementioning

confidence: 99%

Optical manipulation for studies of collisional dynamics of micron-sized droplets under gravity

Ivanov,

Chang,

Galinskiy

et al. 2017

Preprint

0

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A new experimental technique for creating and imaging collisions of micron-sized droplets settling under gravity is presented. A pair of glycerol droplets is suspended in air by means of two optical traps. The droplet relative velocities are determined by the droplet sizes. The impact parameter is precisely controlled by positioning the droplets using the two optical traps. The droplets are released by turning off the trapping light using electro-optical modulators. The motion of the sedimenting droplets is then captured by two synchronized high-speed cameras, at a frame rate of up to 63 kHz. The method allows the direct imaging of the collision of droplets without the influence of the optical confinement imposed by the trapping force. The method will facilitate efficient studies of the microphysics of neutral, as well as charged, liquid droplets and their interactions with light, electric field and thermodynamic environment, such as temperature or vapor concentration.

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“…Its main advantage, thus, is the large working distance of the focusing optics. This property has been used, for example, to determine the electric charge of levitated oil droplets [12].…”

Section: Introductionmentioning

confidence: 99%

Measurement of particle motion in optical tweezers embedded in a Sagnac interferometer

Galinskiy¹,

Isaksson²,

et al. 2015

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We have constructed a counterpropagating optical tweezers setup embedded in a Sagnac interferometer in order to increase the sensitivity of position tracking for particles in the geometrical optics regime. Enhanced position determination using a Sagnac interferometer has previously been described theoretically by Taylor et al. [Journal of Optics 13, 044014 (2011)] for Rayleigh-regime particles trapped in an antinode of a standing wave. We have extended their theory to a case of arbitrarily-sized particles trapped with orthogonally-polarized counterpropagating beams. The working distance of the setup was sufficiently long to optically induce particle oscillations orthogonally to the axis of the tweezers with an auxiliary laser beam. Using these oscillations as a reference, we have experimentally shown that Sagnac-enhanced back focal plane interferometry is capable of providing an improvement of more than 5 times in the signal-to-background ratio, corresponding to a more than 30-fold improvement of the signal-to-noise ratio. The experimental results obtained are consistent with our theoretical predictions. In the experimental setup, we used a method of optical levitator-assisted liquid droplet delivery in air based on commercial inkjet technology, with a novel method to precisely control the size of droplets.

show abstract

Optical manipulation for studies of collisional dynamics of micron-sized droplets under gravity

Ivanov¹,

Chang²,

Galinskiy³

et al. 2017

View full text Add to dashboard Cite

A new experimental technique for creating and imaging collisions of micron-sized droplets settling under gravity is presented. A pair of glycerol droplets is suspended in air by means of two optical traps. The droplet relative velocities are determined by the droplet sizes. The impact parameter is precisely controlled by positioning the droplets using the two optical traps. The droplets are released by turning off the trapping light using electro-optical modulators. The motion of the sedimenting droplets is then captured by two synchronized high-speed cameras, at a frame rate of up to 63 kHz. The method allows the direct imaging of the collision of droplets without the influence of the optical confinement imposed by the trapping force. The method will facilitate efficient studies of the microphysics of neutral, as well as charged, liquid droplets and their interactions with light, electric field and thermodynamic environment, such as temperature or vapor concentration.

show abstract

Manipulation of optically levitated particles

Cited by 3 publications

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Optical manipulation for studies of collisional dynamics of micron-sized droplets under gravity

Optical manipulation for studies of collisional dynamics of micron-sized droplets under gravity

Measurement of particle motion in optical tweezers embedded in a Sagnac interferometer

Optical manipulation for studies of collisional dynamics of micron-sized droplets under gravity

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