Nanooptics and photonics

Characterization of single micrometre-sized droplets with luminescent nanoparticles levitated in linear electrodynamic trap
Derkachov G.1, Fronc K.1, Jakubczyk D.1, Kamińska I.1,
Kolwas M.1, Nyandey K.1, Shopa Y.2
1Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, Warsaw 02-668, Poland.
2Cardinal Stefan Wyszyński University in Warsaw. Faculty of Mathematics and Natural Sciences, Wóycickiego 1/3, 01-938 Warsaw, Poland.
E-mail: i.shopa@uksw.edu.pl

Our latest studies of the dynamic light scattering [1] on microdroplets of suspension in a 3D quadrupole trap have shown that the temporal variation of the autocorrelation function reflects the evolution of the microdroplet. The new optical setup used for the characterization of single micrometre-sized droplets with luminescent nanoparticles (LNP) is based on a linear electrodynamic quadrupole trap (LEQT). The nanoparticles of gadolinium oxide (Gd2O3) doped with Nd3+ ions dispersed e.g. in tetraethylene glycol served as luminescent nanoprobes. Single microdroplets of such suspension were introduced into LEQT with an in-lab built piezoelectric droplet-on-demand injector. The microdroplet under test was firmly trapped in LEQT and illuminated with red (650 nm, 20 mW) and IR (805 nm, 1.5 W) laser beams with perpendicular polarisations. The light scattered by the microdroplet and emitted from it was recorded with a broadband spectrometer. As a result, Mie scattering on the microdroplet and emission spectra of LNPs between 880 and 940 nm were observed simultaneously and analysed.
The luminescence spectra and fluctuations of the scattered light generally reflect the changes in size and structure of the evaporating microdroplet of suspension. The non-coherent light emitted from the LNPs interacts with the optical mode structure of the microdroplet (microresonator) and, in consequence, its intensity exhibits noticeable oscillations. The relative intensity of different spectral lines emitted from LNPs provides additional information on the microdroplet parameters – both local and global.

1.	Derkachov G., Jakubczyk D., Kolwas K., Piekarski K., Shopa Y., Woźniak M. Dynamic light scattering investigation of single levitated micrometre-sized droplets containing spherical nanoparticles // Measurement. -2020. -158. -P. 107681.