Echo speckle imaging of dynamic processes in soft materials.

We present a laser-speckle imaging technique, termed Echo speckle imaging (ESI), that quantifies the local dynamics in biological tissue and soft materials with a noise level around or below 10% of the measured signal without affecting the spatial resolution. We achieve this through an unconventional speckle beam illumination that creates changing, statistically independent illumination conditions and substantially increases the measurement accuracy. Control experiments for dynamically homogeneous and heterogeneous soft materials and tissue phantoms illustrate the performance of the method.

Transport properties of optically thin solid dielectrics from frequency correlations of randomly scattered light: publisher's note.

This publisher's note contains a correction to Opt. Lett.47, 1439 (2022)10.

Transport properties of optically thin solid dielectrics from frequency correlations of randomly scattered light.

Frequency-dependent intensity correlation function measurements can be employed to determine the optical turbidity of solid disordered dielectrics. Here we demonstrate a speckle frequency correlation experiment with a focused beam and using an area detector. We show how to apply frequency correlation measurements to optically thin solid samples with the aim of determining the light diffusion coefficient and transport mean free path ℓ*.

Ultra slow acoustic energy transport in dense fish aggregates.

A dramatic slowing down of acoustic wave transport in dense fish shoals is observed in open-sea fish cages. By employing a multi-beam ultrasonic antenna, we observe the coherent backscattering phenomenon. We extract key parameters of wave transport such as the transport mean free path and the energy transport velocity of diffusive waves from diffusion theory fits to the experimental data.

Acoustic density estimation of dense fish shoals.

Multiple scattering of acoustic waves offers a noninvasive method for density estimation of a dense shoal of fish where traditional techniques such as echo-counting or echo-integration fail. Through acoustic experiments with a multi-beam sonar system in open sea cages, multiple scattering of sound in a fish shoal, and, in particular, the coherent backscattering effect, can be observed and interpreted quantitatively. Furthermore, a volumetric scan of the fish shoal allows isolation of a few individual fish from which target strength estimations are possible.