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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:42 |
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Conference: Bucharest University Faculty of Physics 2021 Meeting
Section: Optics, Spectroscopy, Plasma and Lasers
Title:
Monitorization of droplet evaporation via real-time digital holographic interferometry using a phase only SLM
Authors:
Adrian SIMA (1), Petre Cătălin LOGOFĂTU (2), Mihail Lucian PASCU (2), Ionuț NICOLAE (2)
*
Affiliation:
1) University “Politehnica”of Bucharest, Faculty of Electronics, Telecommunications and Information Technology, Bucharest, Romania (PhD student)
2) National Institute for Laser, Plasma and Radiation Physics, Laser Dept., str. Atomiștilor nr. 409, CP MG-36, Măgurele, jud. Ilfov, Romania, 077125
E-mail
petre.logofatu@inflpr.ro
Keywords:
holographic interferometry, optofluidics, geometric approximation
Abstract:
In a previous study [1] we have shown that it is not possible to investigate via interferometric means the modifications in shape and refractive index within a water droplet if the instrument used for investigation is a plane parallel wave, because the rays are diffracted at large angles, the image of the droplet is distorted beyond recognition and drowned in the spurious information coming from diffraction of the light at the edges of the droplet. Things are different, however, if we use a divergent beam as an instrument of investigation. The image of the droplet is less distorted and confined within a reasonably small space that can be adjusted from the divergence angle. Also, the diffraction at the edges is now sent away at large angles, most of it outside the shadow of the droplet. Moreover, supplementary advantages are drawn from the use of a dynamic digital holographic arrangement which can perform real time observation of the optical path modifications induced by the droplet evaporation. Holographic sequences are recorded on a digital camera sensor, immediately subtracted from the initial hologram. The results are holographic interferograms which are instantaneously and sequentially displayed on a spatial light modulator (SLM) for an instant, optical reconstruction of a real-time holographic interferometry “movie” with a 15 fps display rate. Any changes in the optical path due to evaporation (or any other factors) can be observed in real time in the dynamic fringe pattern generated through SLM reconstruction. For qualitative comparison and quantitative fitting the fringe dynamics induced by the droplet evaporation was also theoretically simulated. This experimental version is a modified and improved version of a holographic arrangement used for the monitorization of the salinity spatial distribution in water [2].
For now, we used this holographic arrangement for the monitorization of the droplet evaporation, but the extension of the technique to the study of more complex phenomena, such as the perturbation of the droplet by inelastic and elastic interaction with a pulsed laser is straightforward.
References:
[1] P. C. Logofătu, F. Garoi, M. Boni, M. L. Pascu, “The study of the properties of water droplets using a Mach-Zehnder interferometer and Mie rigorous diffraction,” Rom. Rep. Phys. 72(1), 403 (2020)
[2] Sima, Adrian; Schiopu, Paul; Logofatu, Petre Catalin, “Real - time digital holographic interferometric measurement of diffusive objects displacements using spatial light modulator,” PROCEEDINGS OF THE 9TH INTERNATIONAL CONFERENCE ON ELECTRONICS, COMPUTERS AND ARTIFICIAL INTELLIGENCE - ECAI 201 (2017)
Acknowledgement:
This work was supported by Romanian Ministry of Education and Research, under Romanian National Nucleu Program LAPLAS VI – contract n. 16N/2019.
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