Generation of the First-Order OAM Modes in Ring Fibers by Exerting Pressure Technology

We have proposed an effective method of generating the first-order orbital angular momentum (OAM) modes in ring fibers. The first-order OAM modes (L = ±1) can be represented as the linear superposition of the HE
₂₁
^even
mode and the HE
₂₁
^odd
mode. Through exerting pressure on the ring fiber by a leverage device, the fundamental mode HE
₁₁
can be coupled into higher order mode HE
₂₁
in broadband wavelength ranging from 1530 to 1600 nm. By adjusting the fiber polarization controller and the pressure value exerted on the fiber, both the positive (L = +1) and negative (L = - 1) OAM modes can be generated separately. Moreover, we have demonstrated that the coupling efficiency from the fundamental mode to the first-order OAM modes at wavelength of 1550 nm can reach 67%.