Dye‐Initiated Chirped Cholesteric Polymer Networks Exhibiting Broadband Dissipative Chiral Photonic Bands

ABSTRACT Chiral photonic materials that selectively control circularly polarized light are of growing interest for optical filtering, sensing, and polarization‐dependent light management. Cholesteric liquid crystal polymers provide a versatile platform for chiral photonics due to their self‐organized helical structure, although their optical response is typically limited to narrow reflective stopbands determined by uniform pitch. Here we show that a dye‐based photoinitiator can act as a structure‐directing element, guiding the formation of a cholesteric polymer network with chirped helical pitch and dissipative chiral photonic coupling. Optical spectroscopy reveals a broadband low‐transmission region far exceeding the bandwidth of uniform‐pitch cholesteric, while preserving handedness‐dependent attenuation. This behavior originates from the interplay between a depth‐dependent helical pitch frozen during photopolymerization and the complex optical anisotropy introduced by aligned dye molecules embedded in the polymer network. The resulting pitch gradient distributes the Bragg condition along the film thickness, while isotropic absorption and linear dichroism render the Bragg interaction intrinsically dissipative. A coupled‐wave model incorporating pitch chirping and complex optical parameters consistently describes the observed broadband attenuation and polarization‐selective response. These findings demonstrate that photoinitiator dyes can actively shape supramolecular organization during polymerization, enabling programmable solid‐state chiral photonic materials with broadband dissipative and polarization‐selective functionalities.