Photonic crystals in proton-exchanged LiNbO3 waveguides for photonic applications

Photonic crystals realized in LiNbO₃ have a great potential to reduce the size and increase the functionality of integrated optical devices. In order to accomplish these aims, fabrication know-how must be mastered yet it remains relatively uncharted. In this work we report the fabrication and optical characterization of photonic crystal structures in annealed proton exchanged (APE) LiNbO₃ waveguides. In our work, channel waveguides were fabricated by photolithography patterning followed by immersing LiNbO₃ wafers in molten benzoic acid at 235°C for 5 h. The thickness and the composition profiles of the APE waveguides were measured using the secondary ion mass spectroscopy (SIMS) method. The experimental characterization of the photonic crystal waveguides was performed and a photonic stop band with good sharpness can be observed from the transmission spectra.