Microstructure in lithium niobate by use of focused femtosecond laser pulses

Using a tightly focused femtosecond laser of microjoule energy per pulse, we produced optical waveguide inside the pure Lithium Niobate (LN) substrate. This technique has the potential to generate not only channel waveguide but three-dimensional photonic devices. In this letter, a Y splitter has been fabricated in LN. The output optical fields through the channel waveguide and Y splitter were measured and compared with theoretical simulation results. The refractive index change of ∼6×10^-4 was obtained with the transmitted-beam near-field method. The properties of channel waveguide and Y splitter were discussed for further study.