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

ABSTRACT 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 1/2 Nb 2/3 )O 3 –Pb(Mg 1/2 Nb 2/3 )O 3 –PbTiO 3 (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 Δ n ≈ 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.