Integrated outstanding precision and mechanical performance of transparent 3D photonic crystal devices employing cross-linked nanospheres via thermoforming in a rubbery state

Photonic crystals act as an advanced quantum and nonlinear optics tool for multi-crystal photonic devices, and they show excellent potential for micro- and nanophotonic systems. Although exciting progress has been witnessed in recent decades, the excessive dependence on visible light reflection and poor mechanical properties make it challenging to directly implement these materials in transparent precision optical equipment. Here, we report a convenient monolithic approach whereby transparent 3D photonic devices with outstanding mechanical properties were assembled from monodisperse nanosphere powder in a high elastic state. Based on Bragg's law, we regulate the optical band gap beyond visible light by controlling the size of the photonic crystal nanospheres. These polymer transparent optical devices exhibit some excellent performance characteristics including high transparency (89%), visible light selective transmission (400-800 nm) and excellent mechanical properties (hardness reaches 0.32 GPa). These properties enable 3D photonic crystal devices to be applied in transparent precision optical components such as the lenses of spectacles, microscopes, telescopes and endoscopes, industrial cameras and astronaut helmets. The work provides an exciting new fabrication route for 3D highly transparent polymer photonic crystal devices, which are difficult to access by simply using traditional methods.