Nanochannels with a 18-nm feature size and ultrahigh aspect ratio on silica through surface assisting material ejection

.Nanochannel structures with a feature size deeply under the diffraction limit and a high aspect ratio hold huge biomedical significance,which is especially challenging to be realized on hard and brittle materials,such as silica,diamond,and sapphire.By simultaneously depositing the pulse energy on the surface and inside the sample,nanochannels with the smallest feature size of 18 nm(∼1∕30λ)and more than 200 aspect ratios are achieved inside silica,the mechanism of which can be concluded as the surface assisting material ejection effect.Both the experimental and theoretical results prove that the coaction of the superficial“hot domain”and internal hot domain dominates the generation of the nanochannels,which gives new insights into the laser-material interacting mechanisms and potentially promotes the corresponding application fields.