Séminaire de l'INPHYNI: Sofía Angriman -- Roberto Gajardo

Exploring turbulence through particle motion: transport and rotation of rods in turbulent flows (Sofía Angriman)

Abstract:
Turbulent flows with suspended particles arise in a wide range of systems, from the dispersion of volcanic ash after an eruption to the airborne transmission of diseases via droplets. The coupling between the flow and suspended objects leads to rich and complex dynamics, and tracking individual particles provides a natural way to approach this complexity, probing not only the influence of turbulence on the particles, but also properties of the underlying flow. After a brief overview of my research background, I will present my current postdoctoral work at INPHYNI on the dynamics of rigid and flexible fibres in turbulence, combining channel flow experiments with numerical simulations in wall-bounded and unbounded flows. I will focus on ongoing numerical results on the transport of long rods, highlighting how their translational dynamics are coupled to rotational motion, such as tumbling and spinning.


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Pulse Generation in Pairs of Nanolasers with non-Hermitian Coupling (Roberto Gajardo)

Abstract:

In coupled-laser systems the interplay of gain, loss and coupling gives rise to collective modes whose properties depend sensitively on interference conditions. In this framework, non-Hermitian coupling provides a route to dynamically tune the effective Q-factor of collective modes, which allows us to store and release energy in the form of short optical pulses (Q-switching). We demonstrate this phenomenon in a pair of phase-coupled photonic crystal nanolasers under asymmetric optical pumping, and explore the properties and stability of pulse generation. A rate-equation model captures the interplay between carrier dynamics and modal coupling, allowing us to reproduce the observed behavior and to study carrier dynamics during the Q-switching process.