A dual-core fiber for tunable polarization splitters in the terahertz regime

We present a new scheme of dual-core THz fiber for tunable polarization splitter based on the mode coupling theory. Each elliptical polymer core is modified with two elliptical air holes, which is helpful for high modal birefringence and low transmission loss. Due to different coupling lengths for x and y polarizations, the two orthogonal polarizations can be easily separated in an appropriate transmission length. Characteristics of the proposed fiber are discussed numerically in detail, including modal birefringence, effective material absorption loss, coupling and splitting length, transmission loss, extinction ratio, tunability. For the THz polarization splitters, 0.865 cm splitting length is numerically demonstrated at the operation frequency of 1 THz. An efficient tuning method is provided that the operation frequency can be tuned by the applied pressure. This tuning method extends the operation frequency bandwidth from 0.9 to 1 THz in the fixed splitting length. This proposed pressure-tuning THz fiber polarization splitter has potential applications in the field of on-chip integrated THz polarization devices and in-fiber integrated optical devices.