Femtosecond laser-induced periodic surface structures on lithium niobate crystal benefiting from sample heating

Periodic surface structures were fabricated by irradiating lithium niobate (LN) crystals with femtosecond laser pulses at sample temperatures ranging from 28°C to 800°C. Carrier density and conductivity of the samples were increased via heating LN, which inhibited coulomb explosion to obtain a uniform periodic surface structure. The periodic surface structures cover an area of 8  mm×8  mm and have an average spacing of 174±5  nm. Meanwhile, the absorption of the processed sample is about 70% in the spectral range of 400–1000 nm, which is one order of magnitude higher than that of pure LN. Fabrication of periodic surface structures on heating LN with femtosecond laser pulses provides a possibility to generate nanogratings or nanostructures on wide-bandgap transparent crystals.