Abstract

There has been much interest in second harmonic generation (SHG) in optical fibres ^1-13 since Osterberg and Margulis ¹ reported a conversion efficiency of 0.5% and demonstrated dye laser pumping. Further work has achieved conversion efficiencies in excess of 10%. The phenomenon has stimulated particular interest in view of the classical theory that there is no second order nonlinearity in an isotropic medium such as fused silica. The results reported clearly indicate the generation of non-inversion symmetry in the fibre as a result of optical excitation. There have been earlier observations ¹⁴ of SHG in fibres but it is not clear if these arise from quadrupole nonlinearities, Raman related 4 wave mixing or optically written gratings. In this paper we review SHG due to optical modification of the fibre.

© 1989 Optical Society of America