Abstract

Subject of study. We investigate the effect of alkaline etching on three types of laser-induced modification within a nanoporous silicate matrix: birefringent structures, densification, and decompaction of the material. Purpose. We study the influence of alkaline etching on the optical and morphological properties of three types of porous glass laser-induced modification: birefringent structures, densification, and decompaction of the material formed by ultrashort laser pulses. Methodology. The technology is implemented in three stages: (i) direct laser writing in the nanoporous silicate matrix using focused (20×, NA=0.4) femtosecond laser pulses (v=25−50kHz, υ=1, 5, 45 mm/s, P=15−60mW, τ=500 and 2000 fs, λ=515nm); (ii) alkaline etching in potassium hydroxide, which cleans up the fabricated tracks, and, in addition, the average pore size increases to 17 nm at this stage; and (iii) purification of the sample in distilled water followed by drying in a furnace. Main results. Conditions are obtained for fabricating hollow microchannels with length and width of 5 mm and 5–7 µm, respectively. The microchannels were also filled with a liquid (volume of 3 µl), that completely evaporated after 10–12 s. The microchannels feature a selective reflection in a narrow visible spectral range. Practical significance. What we believe to be a novel methodology for microchannel fabrication in nanoporous silicate matrix plates is presented. The channel is surrounded by a waveguiding shell that provides further possible applications in optofluidics. The study opens up new possibilities in the development of volumetric microfluidic systems, which is crucial for the study of biochemical reactions or the diagnosis of environmental changes. In the future, such optofluidic elements in a nanoporous silicate matrix can become the focus of important research for novel chip-scale sensor devices or laboratories on a chip (lab on a chip).

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