STIMULATED 4-PHOTON MIXING AND EFFICIENT POLYCHROMATIC VISIBLE-LIGHT GENERATION IN SIO2-BASED SINGLE-MODE OPTICAL FIBERS PUMPED AT 1.319 MU-M

The generation of near-infrared and intense visible light through stim ulated multiwave mixing processes in single-mode silica-based optical fibers pumped by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 mu m is described The experimental results show that intense in frared light around 1.2 mu m is produced via self-phase-matched four-p hoton mixing at the minimum group velocity dispersion region of pure S iO2-core and P2O5-doped silica fibers. In the visible spectral region, from 580 nm to 600 nm, 20 W peak power 100-ps pulses were generated b y pumping single spans of single-mode P2O5-doped and undoped SiO2-core fibers with 1.319-mu m laser pulses. The signal light generated in su ch fibers propagated in the LP(02) fiber mode and exhibited a threshol d power that depended upon the fiber length and a critical length that was power dependent. Also, it exhibited an asymmetrical spectrum of a few nanometers bandwidth, with a long tail toward high frequencies. F or GeO2-doped silica-based fibers, a multiple-wavelength visible signa l propagating in several high-order fiber modes was generated.