Optical Orbital Angular Momentum Amplifier Based on an Air-Hole Erbium-Doped Fiber

We present for the first time broadband operation of an optical orbital angular momentum (OAM) erbium-doped fiber amplifier for lower order OAM modes based on an air-hole erbium-doped fiber designed and fabricated to provide significant mode splitting between the OAM |l| = 1 modes and the adjacent vector modes. Up to 15.7 dB gain is obtained using a cladding pumped amplifier configuration for OAM modes with topological charge |l| = 1 in the operational wavelength range 1545-1600 nm.