Ultra‐Broadband Terahertz Polarization Conversion Enabled by All‐Dielectric Grating Structures

Polarization control of electromagnetic waves has attracted broad interest for years. Despite meaningful efforts in the past decade, how to realize broadband transmissive polarization conversion for terahertz waves is a problem remaining unresolved. Herein, an innovative strategy of designing an all‐silicon grating is proposed, and it is experimentally demonstrated that the designed structure is capable of realizing ultra‐broadband cross‐linear and linear‐to‐circular polarization conversions in the terahertz regime. Moreover, active control of arbitrary polarization states can be accomplished by mechanically tilting the grating structure. In brief, this work promises a new approach to realizing ultra‐broadband conversion in arbitrary polarization state at terahertz frequencies, and is of great significance for terahertz wireless communication technology, polarization imaging, and emergent biochemistry research requiring dichroism light.