Mutual spatio-temporal collapse of femtosecond pulses

Summary form only given. The nonlinear optical process of self-focusing is a result of the intensity-dependent refractive index. If the power of the beam is sufficiently large, the lensing effect induced on the beam due to its radial intensity profile dominates diffraction, and the beam undergoes collapse, which is a practice is eventually halted by higher-order nonlinear processes such as plasma formation. When ultrashort-pulsed lasers are used instead of continuous-wave lasers, temporal effects such as dispersion, self-steepening, and space-time focusing must be accounted for in the high-intensity regime of the collapsing beam. The consequence of these processes under conditions in which the pulse undergoes spatio-temporal collapse is the occurrence of extreme spectral broadening known as super-continuum generation (SCG). We present results that demonstrate that two beams can interact and induce mutual spatio-temporal collapse even though neither beam will undergo collapse by itself. In addition, the beams become radially symmetric which we believe is evidence of the onset of the formation of Townes spatial solitons as the pulses undergo strong self-focusing. In the case in which the two beams overlap temporally, we see that the beam diameters are smaller due to mutual self-focusing and that the two beams attract each other. At this point, we also observe the occurrence of SCG in both beams indicating the mutually-induced collapse of each pulse.