Superradiant Droplet Emission from Parametrically Excited Cavities

Minimal Quantization Model in Pilot-Wave Hydrodynamics

Investigating how classical systems may manifest dynamics analogous to those of quantum systems is a broad subject of fundamental interest. Walking droplets, which self-propel through a resonant interaction with their own wave field, provide a unique macroscopic realization of wave-particle duality that exhibits behaviors previously thought exclusive to quantum particles. Despite significant efforts, elucidating the precise origin and form of the wave-mediated forces responsible for the walker's quantumlike behavior remained elusive. Here, we demonstrate that, owing to wave interference, the force responsible for orbital quantization originates from waves excited near stationary points on the walker's past trajectory. Moreover, we derive a minimal model with the essential ingredients to capture quantized orbital dynamics, including quasiperiodic and chaotic orbits. Notably, this minimal model provides an explicit distinction between local forces, which account for the walker's preferred speed and wave-induced added mass, and spatiotemporal nonlocal forces responsible for quantization. The quantization mechanism revealed here is generic, and will thus play a role in other hydrodynamic quantum analogs.

Coupled instabilities drive quasiperiodic order-disorder transitions in Faraday waves

We present an experimental study of quasiperiodic transitions between a highly ordered square-lattice pattern and a disordered, defect-riddled state, in a circular Faraday system. We show that the transition is driven initially by a long-wave amplitude modulation instability, which excites the oscillatory transition phase instability, leading to the formation of dislocations in the Faraday lattice. The appearance of dislocations dampens amplitude modulations, which prevents further defects from being created and allows the system to relax back to its ordered state. The process then repeats itself in a quasiperiodic manner. Our experiments reveal an unexpected mechanism for temporal quasiperiodicity that results from a coupling between two distinct instabilities on the route to chaos.

Time domain self-bending photonic hook beam based on freezing water droplet

Tunable optical devices are of great interest as they offer adjustability to their functions. Temporal optics is a fast-evolving field, which may be useful both for revolutionizing basic research of time-dependent phenomena and for developing full optical devices. With increasing focus on ecological compatibility, bio-friendly alternatives are a key subject matter. Water in its various forms can open up new physical phenomena and unique applications in photonics and modern electronics. Water droplets freezing on cold surfaces are ubiquitous in nature. We propose and demonstrate the effectual generation of time domain self-bending photonic hook (time-PH) beams by using mesoscale freezing water droplet. The PH light bends near the shadow surface of the droplet into large curvature and angles superior to a conventional Airy beam. The key properties of the time-PH (length, curvature, beam waist) can be modified flexibly by changing the positions and curvature of the water-ice interface inside the droplet. Due to the modifying internal structure of freezing water droplets in real time, we showcase the dynamical curvature and trajectory control of the time-PH beams. Compared with the traditional methods, our phase-change- based materials (water and ice) of the mesoscale droplet have advantages of easy fabrication, natural materials, compact structure and low cost. Such PHs may have applications in many fields, including temporal optics and optical switching, microscopy, sensors, materials processing, nonlinear optics, biomedicine, and so on.

Statistical self-organization of an assembly of interacting walking drops in a confining potential

A drop bouncing on a vertically vibrated surface may self-propel forward by standing waves and travels along a fluid interface. This system called walking drop forms a non-quantum wave-particle association at the macroscopic scale. The dynamics of one particle has triggered many investigations and has resulted in spectacular experimental results in the last decade. We investigate numerically the dynamics of an assembly of walkers, i.e., a large number of walking drops evolving on a unbounded fluid interface in the presence of a confining potential acting on the particles. We show that even if the individual trajectories are erratic, the system presents a well-defined ordered internal structure that remains invariant to parameter variations such as the number of drops, the memory time and the bath radius. We rationalize such non-stationary self-organization in terms of the symmetry of the waves and show that oscillatory pair potentials form a wavy collective state of active matter.