Phase manipulation in reflective phase gradient photonic crystals.

Phase gradient photonic crystals (PGPCs) are proposed as promising candidates for phase manipulation and can enable arbitrary electromagnetic functions, such as deflection and focusing. In stark contrast to the proposed metasurfaces, the phase variation in PGPCs arises from simple edge-configuration rather than structure resonance. Moreover, the reflection magnitude maintains a constant of 1 for the reflective case in the Bragg gap, which affords significant convenience in design. Both theoretical and experimental results demonstrate that the deflector based on reflective PGPCs possesses strong angular stability and is applicable across a broadband frequency range. Our work provides a promising avenue for the implementation of phase manipulation on novel optical platforms, facilitating the development of innovative optical devices with distinctive features in the future.