Self-focusing, breakup and trapping of Raman-shifted femtosecond pulses in homogeneous slab and weakly coupled arrays of nonlinear glass Silica waveguides

摘要

We present experimental and numerical studies of pulse propagation in continuous and periodically modulated nonlinear waveguides, made of Silica glass. When intense femtosecond pulses are passed through this χ_3 material, a positive Kerr nonlinearity is formed. The unique characteristic of glass is accessibility to all domains of possible temporal dispersion (normal, zero and anomalous) in the spectral range of currently available femtosecond pulse sources. In particular, the anomalous dispersion regime enables simultaneous self-focusing in space (X) and time (T), yielding complex dynamics of the beam involving several mechanisms that couple between the X and T dimensions. We show that under certain circumstances, the combination of these mechanisms can lead to simultaneous spatial and spectral filtering in the continuous sample as well as steering of the point of break-up, and beam trapping in the periodic sample, using near-field microscopy and conventional spectroscopy.