In the past two decades, photonics has gained significant momentum in research on subwavelength light control for the design of optical materials with desired electromagnetic properties. Standard methods for fabricating materials with tailored light-matter interaction focus on specific two-dimensional geometrical shapes through nanopatterning, deposition, and lithography. In the case of fully three-dimensional structures, current fabrication techniques are not easily scalable, and they operate mainly with polymer-based materials of relatively low refractive index, limiting the device's performance. This dissertation investigates how suitable materials engineering in three dimensions at the nanoscale can enhance photonic devices, focusing on refractive index sensing and structural coloration applications.  

Here, we demonstrate a simulation framework for the design of optical materials with a user-defined refractive index profile using the geometrical deformation of a reflective substrate. With this framework, we design a nanoresontor with an effective refractive index of n≈100, which we utilize to model an optical sensor with the highest reported sensitivity for a given footprint. We then investigate a low-cost method for fabricating three-dimensional dielectric nanostructures displaying wide-gamut structural colors in high resolution. In the final part, we present a metamaterial exhibiting structural colors tunable by laser exposure. With this metamaterial, we introduce an experimental technique for structural color laser printing with a laser diode at 10 mW of average power.