Second-harmonic generation in periodically poled lithium niobate single-crystal fibres

Periodic ferroelectric domain structures were introduced into lithium niobate (LiNbO/sub 3/) single-crystal fibres by the electric field poling method using a configuration of direct electrode contact. The fibres were pumped with a 1064 nm Nd:YAG laser with a CW input power as high as 1 W. The maximum generated second-harmonic signal was 1.6 mW, thus corresponding to an overall conversion efficiency of 0.016%.