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

Abstract

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 m or from 1.54 to 1.612 m, 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.