Self-focusing collapse distance in ultrashort pulses and measurement of nonlinear index

Self-focusing collapse distance in ultrashort pulses and measurement of nonlinear index.

We analyze the method of moving focus to determine the critical power for self-focusing by means of numerical simulation and a semianalytical model. It is shown that the original interpretation of a moving focus experiment does not hold in general and that inclusion of defocusing effects due to free electrons is necessary to relate the measured data to critical power.

Measurement of Ultrashort Optical Pulses

Resonant radiation and collapse of ultrashort pulses in planar waveguides.

We study the spatiotemporal dynamics of ultrashort pulses close to a point of zero group-velocity dispersion in planar waveguides with focusing nonlinearities. We find that the process of pulse collapse enhances the emission of so-called resonant radiation, providing an efficient mechanism of energy transfer from solitonic to dispersive waves and leading to suppression of the collapse.

Self-focusing Distance of Very High Power Laser Pulses.

We show numerically for continuous-wave beams and experimentally for femtosecond pulses propagating in air, that the collapse distance of intense laser beams in a bulk Kerr medium scales as 1/P;1/2 for input powers P that are moderately above the critical power for self focusing, but that at higher powers the collapse distance scales as 1/P.

Effects of aberrations in spatiotemporal focusing of ultrashort laser pulses.

Spatiotemporal focusing, or simultaneous spatial and temporal focusing (SSTF), has already been adopted for various applications in microscopy, photoactivation for biological studies, and laser fabrication. We investigate the effects of aberrations on focus formation in SSTF, in particular, the effects of phase aberrations related to low-order Zernike modes and a refractive index mismatch betwe...