The development of wafer-scale (3'' diameter) smart-cut lithium niobate (LN) single-crystal films of sub-micrometer
thickness is reported. Z-cut LN wafers, implanted by high energy He-ions, are crystal-bonded to a SiO2 layer on another
Z-cut LN handle sample. The bonded pair of samples splits along the He-implanted layer by appropriate annealing. As
this fabrication method is similar to the process widely used for silicon-on-insulator (SOI) fabrication, the resulting
material is called LNOI.
Two different routes to develop periodically poled LNOI photonic wires are discussed. The first one starts with poling of
planar LNOI samples; the photonic wires are fabricated afterwards by ICP-etching. The second one starts with the
fabrication of LNOI photonic wires; they are "locally" poled afterwards. As both approaches were not yet successful, a
PPLN-substrate was ion beam sliced to generate a planar periodically poled LNOI sample directly.
Using planar LNOI samples as starting material, high-quality photonic wires have been developed. The smallest
structure has a cross-section of ~ 1 x 0.7 μm2 only. Its optical properties with mode distributions, waveguide propagation
losses, and group index were investigated. Moreover, the first periodically poled LNOI photonic wires were successfully
fabricated, but not yet investigated optically. They are of great potential for second order nonlinear integrated optics.