Tunable all-fiber polarization filter based on graphene-assisted metal gratings for the O- and C-bands

All-fiber polarization filters have important applications in optical communication, sensing, and fiber lasing. However, the incompatibility between high extinction ratio and short interaction length is a problem for miniaturization. In addition, current passive designs make polarization filters work in a fixed wavelength band, which limits the dynamic polarization control. Here, we integrate subwavelength metal gratings on graphene-covered D-shaped single-mode fibers to achieve tunable polarization filters, whose operating bandwidth has a significant improvement over previous works. In the simulation, the x-polarized mode couples effectively with the surface plasmon polariton mode and suffers extremely high transmission loss (up to ∼38 dB/mm). At the same time, the y-polarized mode remains low insertion loss of ∼0.58 dB/mm. By changing the chemical potential of graphene, the loss peak of the x-polarized mode can be adjusted in the range covering the wavelength bands from 1.272 to 1.353 µm or from 1.54 to 1.612 µm, which results in an adjustable broadband filter with a high extinction ratio over 20 dB. The proposed filter provides a promising polarization control scheme for integrated devices in the fields of communication, sensing, and lasing.