Multi-Focus Structure and Moving Nonlinear Foci: Adequate Models of Self-Focusing of Laser Beams in Nonlinear Media

Describing the propagation of intense laser pulses in nonlinear Kerr media using the ducting model

“…Only a portion of the initial light beam power flows into the first nonlinear focus. A similar process occurs for other ring zones of the beam, and hence a multi-focus periodic structure will be obtained inside the nonlinear medium [9,10,17].…”

“…Each one of these models has its own advantages and disadvantages and can describe some of the experimentally observed features of pulse propagation in nonlinear Kerr media. Among these models, the multi-focus structure (MFS) [7] and moving nonlinear foci (MNLF) [8] models have been the most developed theoretically and have been confirmed in many experiments, especially for laser pulses with nanosecond durations [9,10]. Indeed, Loy et al [11] investigated the self-focusing of a single-mode ruby laser beam of 8 ns pulse duration in toluene and CS 2 and confirmed the MNLF prediction that the observed filaments are traces of the nonlinear focal locations which move along the propagation axis during that time [9].…”