Stimulated Brillouin gain spectroscopy in a confined spatio-temporal domain (30 μm, 170 ns)

Abstract

The Brillouin gain spectrum of a test sample (liquid acetone at room temperature) on scales simultaneously confined in space (~30 μm) and time (~170 ns) is reported. This is done using a pulsed stimulated Brillouin scattering gain spectrometer in a θ ≈ 90° crossing beam configuration. After having identified and corrected for different sources of background signals, we obtained a Brillouin gain spectrum allowing an accurate measurement (MHz range) of the Brillouin frequency (few GHz). This is of interest for probing acoustic properties of transparent media subjected to repetitive fast transient phenomena on small length scales.

Optical measurement of the equation of state of bulk liquid helium-4 around 1 K

“…that the convolution linewidth of the beating lasers is about 3.5 MHz (FWHM) giving the spectral resolution of the experiment [15]. The other secondary beams, both vertically polarized, are sent towards the experimental cell where the SB gain spectroscopy will be performed.…”

Measurement of the Equation of State of Superfluid Helium-4 at Negative Pressure

“…1 right). In order to measure the compressibility of the metastable states of superfluid 4 He, we have recently developed a Stimulated Brillouin (SB) gain spectrometer capable of measuring the Brillouin frequencies on such a narrow spatio-temporal domain [15,16,17].…”

Stimulated Brillouin Gain Spectroscopy of Superfluid Helium-4

“…The two other secondary beams, both vertically polarized are focused in the experimental cell and overlapped at a crossing angle θ ∼ 90 • [23] using converging lenses of 150 mm and 200 mm focal lengths. Prior to that, the pump and probe beams are expanded with telescopes in order to match their diameters at focus.…”