  We demonstrate a diode laser system which is suitable for high-resolution
spectroscopy in the 1200 nm and yellow spectral ranges. It is based on a
two-facet quantum dot chip in a Littrow-type external cavity configuration. The
laser is tunable in the range 1125 -1280 nm, with an output power of more than
200 mW and exhibits a free-running linewidth of 200 kHz. Amplitude and
frequency noise were characterized, including the dependence of frequency noise
on the cavity length. Frequency stabilization to a high-finesse reference
cavity is demonstrated reducing the linewidth to about 20 - 30 kHz. Yellow
light (> 3 mW) at 578 nm was generated by frequency doubling in an enhancement
cavity containing a PPLN crystal. The source has potential application for
precision spectroscopy of ultra-cold Yb atoms and molecular hydrogen ions.
