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Microstructural modification of lithium niobate crystal induced by femtosecond laser ablation

The morphology and mechanism of lithium niobate (LiNbO3) crystal ablated by a femtosecond laser pulse have been investigated. The ablated spots have been examined by means of scanning electron microscopy (SEM) and atom force microscopy (AFM). Sub-diffraction limit spots in LiNbO3 crystal ablated by femtosecond laser have been obtained. The diameter of ablation spot is 400 nm and 800 nm when 170 nJ single pulse and 100 nJ, 17 pulses were used, respectively. There were about 200nm periodic ripples on the bottom surfaces of the spots at low laser energy. The result shows that the sub-diffraction limit structures may be formed by the multi-photon excitation, and the femtosecond laser ablation is an innovative tool for manufacturing LiNbO3-based optical devices.