Generation of 250 mW narrowband pulsed ultraviolet light by frequency quadrupling of an amplified erbium-doped fiber laser

We demonstrate a high-power, narrowband pulsed source at 390 nm by two stages of frequency doubling in periodically poled MgO:LiNbO(3) and periodically poled KTiOPO(4) of an amplified, passively mode-locked fiber laser. With a frequency quadrupling efficiency of 5.5% and a 0.1 nm bandwidth, the 250 mW ultraviolet source is a suitable compact pump source for many entanglement-based quantum information processing tasks.