Mode-Locked All-Fiber Laser Emitting Two-Color High-Order Transverse Mode

We demonstrate that the mode-locked all-fiber laser can simultaneously emit two-color broadband LP 11 transverse mode in the near-infrared region by sharing a common mode-selective coupler (MSC). The MSC mode converter is designed to achieve simultaneous dual-channel mode conversion corresponding to the wavelength regions at 1.0 and 1.5μm, in which each channel possesses broadband mode conversion from LP 01 to LP 11 mode with high mode purity. As a proof of concept, we implement an all-fiber ytterbium (Yb)- and erbium (Er)-doped fiber lasers with a mode-locked two-color LP 11 modal output. The laser consists of two ring cavities combined with a common MSC mode converter. The generated LP 11 modal pulses have a full width at half maximum of 11 and 8.1 nm for Yb- and Er-doped fiber laser, respectively. The presented fiber laser would represent a promising light source in the field of structured light and ultrafast optics.