Unconventional beam amplification with photovoltaic and diffusion effects in a He+-implanted LiNbO3 : Fe waveguide

Two-wave mixing at 514.5 nm is investigated in an x-cut LiNbO3:Fe waveguide twice implanted with helium ions. The energy transfer is studied in four c onfigurations characterized by the orientation of the optical axis and the polarization of the input waves. It is shown that, in one arrangement, the kinetics of the wave mixing consists of two parts: a transient peak attribu ted to the photovoltaic effect followed by a slower decay toward the statio nary state for which the classic diffusion mechanism is predominant. The ap pearance of the photovoltaic effect is unexpected in comparison with the re sults found for the bulk. (C) 1999 Optical Society of America [S0740-3224(9 9)00102-2].