Structural colour of porous dielectrics processed by direct laser write technique

Abstract

We report realisation of structural colour in dielectrics using direct laser write technique. 3D porous dielectric structures with woodpile photonic crystal architecture were fabricated by femtosecond direct laser write lithography in photoresist and characterised structurally and optically. The fabricated samples were found to exhibit resonant high-reflectance bands at visible wavelengths depending on the lattice parameters, and correspondingly, led to coloration of the structure without light absorption or emission. Structural colour was found to originate from slow-light spectral regions occurring in some higher photonic bands at visible wavelengths. Visible coloration in samples with relatively large lattice period, a > 1μm can be achieved due to this peculiarity, which helps alleviate the requirement for high resolution of the fabrication, shortened the fabrication time. In the future, similar structures may be useful for preparation of photonic crystal-based environmental and imaging sensors.