Self-focusing dynamics of coupled optical beams

Abstract

We theoretically and experimentally investigate the mutual collapse dynamics of two spatially separated optical beams in a Kerr medium. Depending on the initial power, beam separation, and the relative phase, we observe repulsion or attraction, which in the latter case reveals a sharp transition to a single collapsing beam. This transition to fusion of the beams is accompanied by an increase in the collapse distance, indicating the effect of the nonlinear coupling on the individual collapse dynamics. Our results shed light on the basic nonlinear interaction between self-focused beams and provide a mechanism to control the collapse dynamics of such beams. [5]. Over the past decade, with the advent of high peak power ultra-short pulsed lasers, self-focusing dynamics of optical beams have revealed a remarkable richness of spatial and temporal nonlinear phenomena. These include observation of the universal self-similar spatial collapse profile known as the Townes profile [6], multiple filamentation [7], self steepening and pulse splitting [8,9], multiphoton ionization, and supercontinuum generation [9,10], along with saturation and plasma generation that typically arrest the collapse [11].Related optical beam interactions within the context of spatial solitons [12,13] have drawn considerable interest in recent years. Spatial solitons in 1D Kerr media are shown to interact in a particle-like elastic manner, where the number of solitons and the corresponding directions and propagation velocities are conserved [12,14]. Depending on the relative phase, attractive and repulsive forces and power transfer are observed between interacting solitons [15]. In saturable nonlinear media, which can support (2+1)D solitons, phenomena such as soliton fusion, fission, annihilation, and spiraling occur [16,17,18,19]. The interaction between incoherent solitons, where the medium responds non-instantaneously, exhibits similar effects as those observed with coherent solitons in nonlinear saturable media [20].In the regime of optical beam collapse in a Kerr medium, where self focusing is dominant and beams do not maintain their spatial distribution, only a few theoretical studies of beam interactions have been reported [21,22,23,24], and to the best of our knowledge no experiments have been performed. While in these initial theoretical studies several qualitative trends, such as repulsion, attraction, and fusion of two beams, were identified, the detailed dynamics and the transition to fusion of two beams, especially when each beam has a power near P cr , has not been explored.In this Letter, we investigate both theoretically and experimentally the spatial collapse dynamics of two coherently coupled beams in Kerr media. We observe repulsion and attraction between the collapsing beams, and a sharp transition to fusion of the beams, which is dependent on their initial power, spatial separation and relative phase. We further show that this transition, accompanied by a peak in the collapse distance, can be exploited to control and manipulat...

FDTD Computational Study of Ultra-Narrow TM Non-Paraxial Spatial Soliton Interactions

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Ultrashort filaments dynamics of two laser beams propagation in underdense plasmas

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Relative phase interactions of two copropagating laser beams in underdense plasmas at different intensities and spot sizes

“…The relative phase interactions are essential in the regime of the optical beam collapse in the Kerr medium, 13 where the spatial collapse of two coupled beams can be dynamically controlled via the relative phase interactions. Recently in an innovative acceleration concept [14][15][16] of two copropagating laser pulses, a seeding pulse of an ultrashort period and a trailing pulse of a relativity longer period were applied to generate a high amplitude plasma wave.…”