Second harmonic generation capabilities of ion implanted LiNbO3 waveguides

Data are reported on the depth profile of the nonlinear optical capabilities ${\mathrm{(d}}_{33})$ of ${\mathrm{He}}^{+}$ ion-implanted ${\mathrm{LiNbO}}_3$ waveguides. Reflected second harmonic generated light has been measured for guides formed by implant doses ranging from ${\text{5×10}}^{14}$ to ${\text{2×10}}^{16}\hspace{0.17em}{\mathrm{ions/cm}}^2.$ Directly after the irradiation the nonlinearity in the waveguide region is reduced to ∼75% that of virgin ${\mathrm{LiNbO}}_3$ for doses higher than ${\text{3×10}}^{15}\hspace{0.17em}{\mathrm{ions/cm}}^2.$ At the optical barrier the nonlinearity becomes zero for doses above ${\text{1×10}}^{16}\hspace{0.17em}{\mathrm{ions/cm}}^2.$ Annealing at $\text{200\hspace{0.17em}°}\mathrm{C}$ 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.