Abstract: A waveguide to waveguide coupled hybrid master oscillator power amplifier (MOPA) includes a wavelength locked laser master oscillator (MO) first chip including a semiconductor substrate, a waveguide region having a gain section, one side of the MO including an integrated wavelength selective feedback element and the other side of the MO including an integrated reflective or coupling element on one side the waveguide and an emitting surface opposite the integrated reflective or coupling element for emitting light. A power amplifier (PA) second chip is stacked above or below the MO. The PA includes a semiconductor substrate including a waveguide region having a gain section, an integrated reflective or coupling element on a side of the PA aligned with light emitted from the emitting surface of the MO and a coupling grating or turning mirror and integrated lens on an opposite side of the PA for emitting an output beam.