Group delay modulation based on multimode electromagnetically induced transparency

The group delay of passband window plays an important role in the wireless system. Here we propose a controllable group delay structure based on the multimode electromagnetically induced transparency in a closed waveguide system, which is realized by trapping three “dark” modes with high Q‐factors into one “bright” mode with low Q‐factor. Three transparent windows with three discrete peaks of group delay are obtained, whose bandwidth can be adjusted by changing the Q‐factor of each “dark” mode, and then the controllable group delay can be further achieved. Three samples with different distributions of group delay are fabricated and tested. Good agreement between simulated and measured results are presented. The proposed method and structures contribute to the design of passive radio frequency identification (RFID) tags, sensors, multimode filters, slow light components, and novel group‐delay modulator.