Suppression of Higher Order Modes in a Few-Transverse-Mode Er-Yb Co-Doped Fiber Laser Oscillator

We propose and experimentally demonstrate a novel approach for the suppression of higher-order-mode oscillation in a few-transverse mode laser oscillator by decreasing the cavity length. This approach works without any cladding mode filtering. When used in forward pumping configuration, it allowed us to create a master oscillator – power amplifier system with 7 W of output power limited by the onset of Yb self-pulsing, without additional components.