  We present a resonantly frequency-doubled tapered amplified semiconductor
laser system emitting up to 2.6 W blue light at 400 nm. The output power is
stable on both short and long timescales with 0.12% RMS relative intensity
noise, and less than 0.15%/h relative power loss over 16 hours of free running
continuous operation. Furthermore, the output power can be actively stabilized,
and the alignment of the input beams of the tapered amplifier chip, the
frequency doubling cavity and-in case of fiber output-the fiber can be
optimized automatically using computer-controlled mirrors.
