Exploring extreme thermodynamics in nanoliter volumes through stimulated Brillouin-Mandelstam scattering

Andreas Geilen; Alexandra Popp; Debayan Das; Saher Junaid; Christopher G. Poulton; Mario Chemnitz; Christoph Marquardt; Markus A. Schmidt; Birgit Stiller

arXiv · 2208.04814

Exploring extreme thermodynamics in nanoliter volumes through stimulated Brillouin-Mandelstam scattering

Andreas Geilen·Alexandra Popp·Debayan Das·Saher Junaid·Christopher G. Poulton·Mario Chemnitz·Christoph Marquardt·Markus A. Schmidt·Birgit Stiller

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Abstract

Examining the physical properties of materials - particularly of toxic liquids - under a wide range of thermodynamic states is a challenging problem due to the extreme conditions the material has to be exposed to. Such temperature and pressure regimes, which result in a change of refractive index and sound velocity can be accessed by optoacoustic interactions such as Brillouin-Mandelstam scattering. Here we experimentally demonstrate Brillouin-Mandelstam measurements of nanoliter volumes of liquids in extreme thermodynamic regimes. We use a fully-sealed liquid-core optical fiber containing carbon disulfide; within this waveguide, which exhibits tight optoacoustic confinement and a high Brillouin gain of (32.2 $\pm$ 0.8) 1/(Wm), we are able to conduct spatially resolved measurements of the Brillouin frequency shift. Knowledge of the local Brillouin response enables us to control the temperature and pressure independently over a wide range. We observe and measure the material properties of the liquid core at very large positive pressures (above 1000 bar), substantial negative pressures (below -300 bar) and we explore the isobaric and isochoric regimes. The extensive thermodynamic control allows the tunability of the Brillouin frequency shift of more than 40% using only minute volumes of liquid. This work opens the way for future studies of liquids under a variety of conventionally hard-to-reach conditions.

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Andreas Geilen, Alexandra Popp, Debayan Das, Saher Junaid, Christopher G. Poulton, Mario Chemnitz, Christoph Marquardt, Markus A. Schmidt, Birgit Stiller. 2022-08-09. Exploring extreme thermodynamics in nanoliter volumes through stimulated Brillouin-Mandelstam scattering. https://arxiv.org/abs/2208.04814

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