Subwavelength direct laser writing by strong optical nonlinear absorption and melt-ablation threshold characteristics

In this work, we propose nonlinear absorption and melt-ablation threshold characteristics induced subwavelength direct laser writing. The writing materials need to have two features: one is strong nonlinear absorption, and the other is melt-ablation threshold characteristics. According to the strong nonlinear absorption and melt-ablation threshold characteristics of AgInSbTe thin films, the effective energy absorption spot is calculated. The results indicate that the full width at half maximum of the effective energy absorption spot is about 2/5 the original spot. If only the energy intensity above 80% maximum can induce the melt-ablation, the direct laser writing mark size or linewidth can be reduced to 0.14λ/NA (NA denotes numerical aperture), which is only about 0.115 times the original spot size. The calculated results are verified, where the mark size is reduced to about 1/8 the real spot.