High power UV pulsed laser with LMA tapered fiber

A short-pulse Yb-doped fiber laser is reported to yield more than 50 W of UV light after single-pass second- and thirdharmonic generation using LBO crystals. The NIR laser generates ns-mJ pulses with average power exceeding 200 W after multipart fiber amplifier stages. The polarization-maintaining LMA tapered fiber used as the last amplifier stage features near diffraction-limited output, narrow linewidth and high polarization extinction ratio. Conversion efficiency from NIR to UV is found near 30%, with output pulse energy as high as 260 μJ for an oscillator pulse repetition frequency of 200 kHz. Generated UV light is seen close to diffraction limit, with M² factor measured < 1.3 both along and perpendicular to walk-off axis.