Wavelength Dependent Light Trapping in a Chirped 3D Photonic Crystal

Photonic crystals (PC) constitute materials of high interest in photonics providing a unique ability to tailor the light propagation and light-matter interaction. Different technological approaches allow for precise fabrication of perfectly periodic PC implementing different materials and geometries. When the periodicity is chirped (gradually varied) along the propagation direction, the PC achieves chromatically resolved light localization at different positions inside the structure [1], [2]. Although this phenomenon has been studied in 1D and 2D PCs [1], [3], research is more complex for 3D structures due to fabrication challenges. Spectral-dependent light localization and field enhancement has been numerically demonstrated in 3D woodpile PC with an adiabatic period chirp along the propagation direction, and it has been experimentally demonstrated in the microwave regime [4]. However, the observation of this effect in the visible or infrared regime requires downsizing the structure to the micron scale, which presents a challenge both in fabrication and experimental measurement.