Bragg reflection and conversion between helical Bloch modes in chiral three-core photonic crystal fiber

Abstract

Optical fiber modes carrying orbital angular momentum (OAM) have many applications, for example in modedivision-multiplexing for optical communications. The natural guided modes of N-fold rotationally symmetric optical fibers, such as most photonic crystal fibers, are helical Bloch modes (HBMs). HBMs consist of a superposition of azimuthal harmonics (order m) of order A (m) = A (0) + mN. When such fibers are twisted, these modes become circularly and azimuthally birefringent, that is to say HBMs with equal and opposite values of A (0) and spin s are non-degenerate. In this paper we report the use of Bragg mirrors to reflect and convert HBMs in a twisted three-core photonic crystal fiber, and show that by writing a tilted fiber Bragg grating (FBG), reflection between HBMs of different orders becomes possible, with high wavelength-selectivity. We measure the nearfield phase and amplitude distribution of the reflected HBMs interferometrically, and demonstrate good agreement with theory. This new type of FBG has potential applications in fiber lasers, sensing, quantum optics and in any situation where creation, conversion and reflection of OAM-carrying modes is required.

Erratum to “Bragg Reflection and Conversion Between Helical Bloch Modes in Chiral Three-Core Photonic Crystal Fiber”

“…ubsequent analysis has revealed that the dispersion relation in Eq. (3) in this paper [1] is incorrect, because it does not take proper account of the transformation from the helicoidal to the cartesian frame. The correct analysis has been reported in detail in a recent paper [2].…”