Improved fabrication of circular-grating microstructured devices using partially spatially incoherent ultraviolet laser light

We report an effective and practical method for improving the fabrication quality of microstructures by reducing the optical coherence when a dye-doped photoresist thin film is exposed to an ultraviolet laser light source through a transparency photomask with a circular-grating pattern. By using a rotating diffuser to transform the coherent ultraviolet laser light into a low coherence light source instead, the laser light-induced defects of the fabricated microstructured device can be reduced substantially. Besides, we have also demonstrated that as the coherence level of the partially spatially incoherent ultraviolet laser light is lowered successively, the quality of the ring-shaped microstructures can be improved gradually.