Enhanced nonlinear optics with photonic-crystal and microstructure fibers

The mode structure of supercontinuum emission generated by 40-fs pulses of 800-nm Ti: sapphire laser radiation in fused silica microstructure fibers is experimentally studied. The long-wavelength and visible parts of supercontinuum emission are shown to be spatially separated in microstructure-fiber modes. With an appropriate spectral filtering, bell-shaped modes of the long-wavelength section (similar to720--900 nm) of the supercontinuum generated in a microstructure fiber with a small core diameter can be separated from either doughnut-like or bipartite modes of the visible part (similar to400--600 nm) of this supercontinuum. This effect can be employed to spectrally slice single modes of supercontinuum emission from microstructure fibers.