Two-photon polymerization of defects in photonic crystals

Three dimensional (3D) photonic bandgap (PBG) materials have been proposed as the basis of many devices (e.g. low-threshold lasers, low-loss waveguides, and on-chip circuitry), the majority of which rely on the incorporation of defects to provide functionality. While, self-assembled photonic crystals are the most widely explored fabrication route to 3D PBG materials, a critical limitation to their utility for PBG-based applications was the lack of an inherent method to controllably incorporate defect structures. We successfully demonstrated the use of two-photon polymerization (TPP) to generate such embedded features within colloidal crystals.; TPP is a high-resolution, 3D free-form fabrication technique that has been used to define a variety of structures, including microchannels, cantilevers, and photonic crystals. Here, TPP was adapted for use within colloidal crystals to embed pre-defined, 3D, high resolution features. A modulated beam rastering approach was employed and TPP response diagrams were developed to enable the reliable definition of TPP features. Also, preliminary work writing TPP features in 3D holographic photonic crystals was presented.; For applications requiring a complete PBG, it is necessary to convert colloidal photonic crystals to higher refractive index structures that exhibit complete PBGs. To this end, self-assembled photonic crystals with embedded TPP features were replicated in silicon. The TPP features and colloidal crystal served as a template for the final structure---a silicon-air inverse opal (which may exhibit a complete PBG) with embedded air defects. Embedded planar defects in silicon colloidal photonic crystals were optically characterized and high resolution embedded air defects in silicon-air inverse opals were demonstrated, representing a major step forward in providing a platform for the utility of colloidal photonic crystals for PBG-based applications.