Mode-controlled colors from microstructure fibers

We experimentally demonstrate mode-controlled spectral transformation of femtosecond laser pulses in microstructure fibers. Depending on the waveguide mode excited in the fiber, 30-fs Ti: sapphire laser pulses can either generate a broadband emission or produce isolated spectral components in the spectrum of output radiation. This method is used to tune the frequencies dominating the output spectra, controlled by phase matching for four-wave mixing processes. (C) 2004 Optical Society of America.