Method of Generating Femtosecond Cylindrical Vector Beams Using Broadband Mode Converter

We experimentally obtain femtosecond cylindrical vector beams based on a mode-locked fiber laser (MLFL) by using a fused few-mode coupler. Pulses of 300 fs duration with radially and azimuthally polarized modes are directly delivered at the central wavelength of 1566 nm. The fused few-mode fiber coupler inserted inside the cavity acts as a mode converter from LP01 mode to LP11 mode with a wide bandwidth over 100 nm. The proof-of-concept generation of femtosecond cylindrical vector beams is efficient and useful in MLFLs.