High power LP11 mode supercontinuum generation from an all-fiber MOPA.

High power LP11 mode supercontinuum is generated from 25/250 large mode area (LMA) fiber. A mechanical long period grating (LPG) is utilized to control the transverse modes in the LMA fiber to realize the LP11 mode supercontinuum generation in a master oscillator power amplifier (MOPA) configuration. The generated LP11 mode supercontinuum covers the spectral range from ~900 nm to ~2100 nm with a -30-dB spectral width of ~1200 nm and 50% optical to optical conversion efficiency. The seed laser produces picosecond pulses with 1 MHz repetition rate at the wavelength of 1060 nm. After multi-stage amplification in ytterbium-doped fibers, the average output power is scaled to 54.51 W and 56.79 W respectively for LP11 and LP01 mode, accompanying supercontinuum generation. Obvious difference of supercontinuum generation between the LP01 and LP11 modes is experimentally observed due to the different dispersion characters.