Atomic Physics Seminars

Atomic
Thursday, January 20, 2022
3:30 PM
Physics Building, Room 204
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"Spatial symmetry breaking in Kerr-lens mode-locked lasers – beyond the soliton model"


Avi Pe'er , Bar-Ilan University
[Host: Prof. Olivier Pfister]
ABSTRACT:

Kerr-lens mode-locking (KLM) is the work-horse mechanism for generation of ultrashort pulses, where a non-linear lens forms an effective ultrafast saturable absorber within the laser cavity. According to standard theory, the pulse in the cavity is a soliton, with a temporal profile and power determined by the non-linearity to exactly counteract diffraction and dispersion, resulting in pulses, whose power and shape are fixed across a wide range of pump powers. I will present an experimental demonstration and theoretical modeling that a KLM laser in a linear cavity deviates from the soliton model due to the non-local Kerr lens. By breaking the spatial symmetry in the cavity between the forward and backward halves of the round-trip the laser efficiency can surpass the soliton limit in a single pulse, while maintaining stable cavity propagation. We model  the symmetry breaking by numerical simulation and confirm it experimentally in a mode-locked Ti:Sapphire laser with a quantitative agreement to the simulation results. Our numerical tool opens a new window into the crux of mode-locking physics by direct examination of the spatio-temporal dynamics within the Kerr medium, which is difficult (or even impossible) to observe experimentally.

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