PIN-PMN-PT Surface Planar Waveguides Realized via He⁺ Implantation

Owing to their outstanding electro-optic (EO) coefficients, relaxor ferroelectric crystals are promising candidates for next-generation integrated optoelectronic devices, particularly high-performance EO modulators. However, the realization of high-performance EO modulators relies on high-quality optical waveguides, which remains a critical challenge for relaxor ferroelectric crystals. Here, we report the fabrication of a planar waveguide in surface layer of the Pb(In_1/2Nb_2/3)O₃-Pb(Mg_1/2Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) relaxor ferroelectric single crystal using the He⁺ ion implantation technique. He⁺ implantation generates a subsurface damaged layer confined hundreds of nanometers below the crystal surface within the submicron range, whereas the overlying near-surface region retains a pristine single-crystal lattice. Moreover, the energy range of He ion implantation is 100-380 keV, and the damaged layer exhibits a reduced refractive index (maximum Δn ≈ 2.8%), which supports well-defined waveguide modes in the surface crystalline layer, as proved in the prism coupling measurement. The reconstructed refractive index profiles of the He⁺-implanted waveguide exhibit a characteristic optical barrier structure. This work not only clarifies the effects of He⁺ ion implantation on the structural properties of the PIN-PMN-PT single crystal but also provides an effective strategy for fabricating surface planar optical waveguides, thereby addressing a critical bottleneck for the application in integrated EO modulators.