Uniform deep-subwavelength ripples produced on temperature controlled LiNbO_3:Fe crystal surface via femtosecond laser ablation

摘要

In this paper, we studied the femtosecond laser induced periodic surface structures (fs-LIPSS) formation on LiNbO3:Fe crystal with the assistance of elevated temperature. Uniform deep-subwavelength fs-LIPSS with the period of 190 +/- 10 nm was successfully fabricated on crystal surface as the sample temperature was at 1000 degrees C. And the measurement of Transmission Electron Microscopy showed that fs-laser treated samples remained crystalline. We believed that thermal excitation plays a critical role in the formation of fs-LIPSS. The initial carrier density of LiNbO3:Fe are effectively increased during this process, and high concentration surface carriers are effectively excited by femtosecond laser irradiation, which make great contribution to formation of fs-LIPSS. Moreover, we also found that the doped Fe2+ ions are conducive to the fs-LIPSS formation. The iron doped LiNbO3 crystal with uniform surface structure has great application prospects in related fields, such as on-chip photonic-integrated platforms, nanophotonics, and nanostructures for micro-fluidics.