UV enhancement and erasure of second-harmonic generation in germanosilicate fibers

Exposure of germanosilicate fibers to cw UV light at 351.1 nm from an argon-ion laser is shown to have dramatic effects on the seeded preparation of the material for second-harmonic generation. We show that 100 microW of 351.1-nm radiation for periods as short as 20 s leads to large, permanent enhancements of the second-harmonic conversion efficiency. The UV exposure provides an increase of 7 orders of magnitude in final conversion efficiency in one regime of IR preparation intensity and allows preparation with cw IR and second-harmonic wavelengths. In addition, the 351.1-nm wavelength was shown to erase the chi((2)) grating much more efficiently than did 514.5-nm radiation.