Realization of a broadband terahertz wavelength-selective coupling based on five-core fibers

We propose a novel kind of wavelength-selective coupling for the terahertz range based on solid five-core fiber (FCF). The performances of coupling, propagation characteristics, and confinement loss properties are numerically investigated by using a full vector beam propagation method (BPM). Simulation results show that it is possible to realize a broadband wavelength-selective coupling. The coupling length can reach 1.913 cm, and the confinement loss is better than 1.965× 10^-4 cm^-1. Furthermore, a parameter, the power difference, is defined, and it numerically demonstrates the working performance of the wavelength-selective coupler; that is, when the power difference is better than -15 dB, the frequency located in the range of 0.76 THz-1.00 THz is separated relatively well from the frequency of 0.3 THz. Finally, the effect of the structural parameter on the working performance of the coupler is also investigated. We show that the performance optimization is possible by appropriately tuning the core diameter, and the tunabilities of frequency and bandwidth are possible by appropriately tuning the pitch. The wavelength-selective coupler is of potential application for optical fiber sensing and communication in terahertz wavelength division multiplexer fields.