Electronic paramagnetic resonance study of Cu2+ ions in copper ion-exchanged layers of lithium niobate crystals

Copper-doped LiNbO3 layers prepared by an Cu\u2013Li ion-exchange process are characterized by electronic paramagnetic resonance. It is found that the majority of Cu2+ ions are coupled by strong exchange interactions which is characteristic of short distances between paramagnetic ions. Such ions are accumulated in a thin layer near the crystal surface and can enter in new crystalline phases formed as a result of the Cu\u2013Li ion exchange. A small amount of Cu2+ ions is incorporated into weakly distorted LiNbO3 crystal lattice inside the diffusion layer

Copper-lithium ion exchange in LiNbO3

Copper-doped LiNbO3 waveguides were prepared by Cu\u2013Li ion-exchange process. Compositional, structural, and optical analyses were performed by secondary ion mass spectrometry, x-ray diffraction, and m-line spectroscopy, respectively. The chemical state of Cu2+ ions was studied by electron paramagnetic resonance, and the results were correlated with structural modification of the LiNbO3 matrix. Copper incorporation in the crystal took place under different regimes, and it induced a lattice rearrangement with the formation of new crystalline phases. Cu2+ ions were surrounded by tetragonally compressed octahedra with rhombic distortions. Cu:LiNbO3 optical waveguides were formed supporting two optical modes