EFFICIENT FREQUENCY UP-CONVERSION OF 1.064-MU-M AND 1.319-MU-M NDYAG LASER-PULSES INTO INTENSE VISIBLE-LIGHT IN SILICA-BASED OPTICAL FIBERS

Single-pass efficient frequency upconversion of 1.064- and 1.319-mum Q -switched and mode-locked Nd:YAG laser pulses into visible-wavelength light in the range 450-600 nm in silica-based monomode optical fibers is reported. The visible upconverted signal propagates in the LP02 fib er mode and exhibits an asymmetrical wide-bandwidth spectrum of severa l nanometers with a long tail toward high frequencies. At both pump wa velengths the upconversion process presents a critical fiber length of a few meters and a threshold power that depends on the fiber length a nd the pump wavelength. It is also observed that the visible light sig nal has its peak wavelength centered on higher frequencies for fibers with longer minimum dispersion wavelengths. In pure SiO2-core fibers p umped at 1.319 mum, conversion efficiencies of approximately 0.5% were obtained, and a 20-W peak power upconversion signal was generated at 580 nm.