Mopa laser source with wavelength control

The invention provides a wavelength-controlled pump MOPA laser and a method of operation thereof. A monolithic semiconductor MOPA laser chip (100) has a DFB-laser based master oscillator (120) and a power amplifier section (130) formed in a same monolithic waveguide, and separate MO and PA electrodes (111,112) for individual control of current injection into the MO and PA sections. The laser wavelength is defined by the DFB grating (150) and is kept fixed by suitably controlling the MO current to compensate for a thermal crosstalk from the PA section, or tuned by suitably changing the MO current or direct heating of the DFB region. Stabilisation may be performed with a photodetector at the output and a look-up table in order to control the currents provided to the MO and the PA section.