Second harmonic generation capabilities of ion implanted LiNbO3 waveguides

Data are reported on the depth profile of the nonlinear optical capabilities (d(33)) of He+ ion-implanted LiNbO3 waveguides. Reflected second harmonic generated light has been measured for guides formed by implant doses ranging from 5 X 10(14) to 2 X 10(16) ions/cm(2). Directly after the irradiation the nonlinearity in the waveguide region is reduced to similar to 75% that of virgin LiNbO3 for doses higher than 3 x 10(15) ions/cm(2). At the optical barrier the nonlinearity becomes zero for doses above 1 x 10(16) ions/cm(2). Annealing at 200 degrees C completely recovers the nonlinearity of the waveguiding layer, as well as reducing absorption losses within the guide. For the highly disordered material in the barrier, the harmonic signal shows that only partial recovery of the structure occurs, even by annealing at higher temperatures. This difference in response allows the production of low loss waveguides with high nonlinearity. (C) 1998 American Institute of Physics. [S0021-8979(98)04421-1].