High-Order Operating Mode Selection Using Second-Order Bandgap in THz Bragg Fiber

This paper demonstrates a novel design technique for single-TE01-mode Bragg fiber using a second-order bandgap achieving signal propagation loss less than 1.2 dB/m from 0.85 THz to 1.15 THz. The TE01 mode intrinsically has a null point in the electric field close to the interface region between the core and the cladding. This makes the TE01 mode preferable to other modes since it shows low signal propagation loss and low electromagnetic interference from cladding defects. Bragg fiber can exhibit a strong mode selectivity as a result of modal-filtering effects. A large loss discrimination between the desired TE01 mode and competing modes can be designed by appropriately tailoring the photonic bandgap.