Soliton beam propagation; space-time behaviour and spectral features

Abstract

Single mode laser beams may suffer from unstable breakdown (self-focusing) in materials exhibiting power dependence of their refractive index. This well-known instability appears suddenly above the 'critical self-focusing power threshold'. It disappears if so-called 'soliton propagation' conditions are met: diffraction of two-dimensional field distribution obeying the Schrodinger equation with cubic nonlinearity. Presented experiments effectively demonstrate the stable single mode self-confinement of suitably shaped laser beam by its self-induced refractive index gradient, due to optical Kerr nonlinearity. Field intensity requirements (tens of megawatts per square millimeter) for soliton observation in CS₂ led to working with a pulsed mode-locked laser source.