Phase-matched nonlinear interactions in a holey fiber induced by infrared super-continuum generation

By coupling 110-fs pulses at lambda = 1.55 mum into a 45-cm-long holey fiber, we observe the generation of a broadband continuum, followed by the appearance of a sharp blue line at 430 nm. Blue light is generated in a high-order mode by a third-harmonic generation process that is phase-matched with the super-continuum component at 1.29 mum. Such an interpretation is supported by measurements performed by using 1.29-mum pulses and also by simulation. In addition we find that the choice of an input polarization tilted with respect to the fiber-birefringence axis can lead to the generation of new frequencies through a four-wave mixing process that exploits non-diagonal components of the third-order susceptibility. (C) 2002 Elsevier Science B.V. All rights reserved.