Over 55W of frequency doubled light at 530 nm pumped by an all-fiber diffraction limited picosecond fibre MOPA

We report the realisation of a high power, picosecond pulse source at 530 nm pumped by an all-fiber, single mode, single polarisation, Yb-doped MOPA. The pump MOPA comprised of a gain switched seed source generating 20 ps pulse source at a repetition frequency of 910 MHz followed by three amplification stages. Output power in excess of 100 W was obtained at 85% slope efficiency with respect to launched pump power at 975 nm. A 15mm long LBO crystal was used to frequency double the single mode, single polarisation output of the fiber MOPA. To satisfy the phase matching condition, the internal temperature of the LBO crystal was maintained at 1550C. Frequency doubled power in excess of 55 W was obtained at 56% optical-to-optical conversion efficiency. Output power at 530 nm started to roll-off after 50 W due to self-phase modulation (SPM) assisted spectral broadening of the fundamental light within the final stage amplifier. Measured spectral bandwidth of the frequency doubled signal remained at ~0.4 nm with the increase in fundamental power even though that of the fundamental increased steadily with output power and reached to a value of 0.9 nm at 100 W output power. © 2010 Copyright SPIE - The International Society for Optical Engineering.