Optical waveguide in stoichiometric lithium niobate by multi-low-energy helium ion implantation

In this letter, we report on the fabrication of planar optical waveguide in stoichiometric lithium niobate by four-low-energy Helium ion implantation with relative low doses. The simulated refractive index profile reveals that the index-raised well exists in the near-surface ion implanted region. There are dark modes with positive changes of effective refractive indices measured by the prism coupling technique both at 633 and 1539 nm after annealing. Further, the small and homogenous damage depth profile proves that there should be the refractive index with positive change. Large energy of the modes is confined in the guiding region. The light was confined well in the waveguide by broad and homogenous index-raised region. Propagation loss for extraordinary refractive index is estimated to be ∼1.2 dB/cm.