2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/113077This letter describes the design and operation of a polymer-based third order distributed feed-back (DFB) microfluidic dye laser. The device relies on light-confinement in a nano-structured polymer film where an array of nanofluidic channels is filled by capillary action with a liquid dye solution which has a refractive index lower than that of the polymer. In combination with a third order DFB grating, formed by the array of nanofluidic channels, this yields a low threshold for lasing. The laser is straight-forward to integrate on Lab-on-a-Chip micro-systems where coherent, tunable light in the visible range is desired.4 pages, 3 figuresOpticstext