Phys.org  September 25, 2023
Pressure is encountered in various fields – atmospheric pressure in meteorology, blood pressure in medicine, etc. Examining the physical properties of materials under a wide range of thermodynamic states is a challenging problem due to the extreme conditions the material must experience. Such temperature and pressure regimes, which result in a change in the refractive index and sound velocity, can be accessed by optoacoustic interactions such as Brillouin–Mandelstam scattering. An international team of researchers (Germany, France, Australia) demonstrated the Brillouin–Mandelstam measurements of nanolitre volumes of liquids in extreme thermodynamic regimes enabled by a fully sealed liquid-core optical fibre containing carbon disulfide. Within this waveguide, which exhibited tight optoacoustic confinement and a high Brillouin gain, they were able to conduct spatially resolved measurements of the local Brillouin response, which gave access to a resolved image of the temperature and pressure values along the liquid channel. They measured the material properties of the liquid core at very large positive pressures (above 1,000 bar) and substantial negative pressures (below –300 bar), as well as explored the isobaric and isochoric regimes. The extensive thermodynamic control allowed the tunability of the Brillouin frequency shift of more than 40% using only minute volumes of liquid… read more. Open Access TECHNICAL ARTICLE
Sample geometry and analysis of the integrated Brillouin spectrum at room temperature… Credit: Nature Physics, September 25, 2023Â