Amplification of high-order azimuthal mode based on a ring-core Yb-doped fiber

Abstract

In order to increase the number of amplified azimuthal modes in Yb-doped fiber (YDF), a multiple azimuthal modes amplifier based on a ring-core Yb-doped fiber (RC-YDF) was proposed and demonstrated. A home-made RC-YDF which can support 6 azimuthal mode groups was employed to amplify the signal mode at 1 064 nm, using a core pump scheme. The amplification characteristics of 5 high-order azimuthal linear polarization (HA-LP) mode groups (LP₁₁, LP₂₁, LP₃₁, LP₄₁, LP₅₁) were studied comprehensively. A more than 8 dB gain is obtained for each signal mode with 5 dBm input power, and the associated differential modal gain between all modes is less than 1 dB. The intensity profiles of all modes are stable and well preserved during the process of amplification.