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Soliton-pair dynamical transition in mode-locked lasers, Kfir Sulimany^, Offek Tziperman^, Yaron Bromberg, Omri Gat. ^equal contribution

Multi-soliton mode-locked laser waveforms are much sought as a complex light source for research and applications, but are difficult to manipulate effectively because of the elaborate and diverse interactions present. Here we present an experimental, numerical, and theoretical study of the interaction and control of the internal dynamics of a two-soliton waveform in a mode-locked fiber laser. Using the pumping current as a control agent, we demonstrate experimentally a two-orders-of-magnitude reduction in the separation of a bound soliton pair, inducing a dynamical transition between a loosely bound, phase-incoherent pair, and a tightly bound phase-locked pair. We show on the basis of a Haus-model numerical simulation of the recently-proposed noise-mediated interaction theory, that the pulse separation and dynamical transition are governed by the shape of the dispersive-wave pedestals. We explain the dynamical transition by showing analytically, within a simplified theory, that the noise-mediated interaction becomes purely attractive when the pedestals energy drops below a threshold. This work demonstrates the ability to control the waveform through the interaction forces, without external intervention in the light propagation in the laser.

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Clump Survival vs Disruption by Supernova Feedback - In preparation, Avishai Dekel, Offek Tziperman et al

Addressing the giant clumps in high-redshift disc galaxies, we evaluate the conditions for clump survival versus disruption by supernova feedback in a disc dynamical timescale. We compare the energy deposited by supernova bubbles in the clump gas to the its gravitational binding energy in the clump, in the spirit of (Dekel & Silk 1986) and Toomre violent disk instability (Dekel, Sari & Ceverino 2009). We find that long-lived clumps tend to exist above a clump threshold mass, near the Toomre mass, in galaxies above a critical mass, above a threshold gas fraction, and with relatively low central mass of bulge and dark matter. They are not expected to exist if the energy per supernova is well above the typical value, if the stellar initial mass function is top-heavy, or if the star-formation-rate efficiency is higher than commonly assumed. Status: In preparation