3D Holographic Photonic Crystals Containing Embedded Functional Features

Lack of good ways to incorporate functional features and materials into 3D architectures has impeded progress in 3D photonic crystals (PhCs). Utilizing a modified transfer printing strategy, this study demonstrates the introduction of functional external materials of a diversity of form‐factors into the interior of holographically defined 3D PhCs. PhCs containing solid SU‐8 features, layers of porous silicon (PSi) or emissive LaF₃:Nd³⁺ nanocrystals, and silica colloids are formed. For the LaF₃:Nd³⁺ layer, both enhancement (≈50%) and suppression (≈25%) of the spontaneous emission (λ ≈ 1.32 μm) could be realized by modifying the position of the photonic crystal stop band relative to the rare earth emission. Finite‐difference time‐domain simulations suggest the observed spontaneous emission modification is a result of Bragg mirror‐like reflection, while the measured enhancement is likely caused by the spontaneous emission coupling to a defect mode. Via electrodeposition, this study demonstrates structural inversion of a low refractive index photonic crystal (photoresist‐based) to a high (Cu₂O) refractive index contrast photonic crystal in the presence of an embedded defect, providing an opportunity to enhance the light‐matter interactions using a materials system with transparency in the visible.