Abstract: Systems, devices, and methods of manufacturing optical engines and laser projectors that are well-suited for use in wearable heads-up displays (WHUDs) are described. Generally, the optical engines of the present disclosure integrate a plurality of laser diodes (e.g., 3 laser diodes, 4 laser diodes) within a single, hermetically or partially hermetically sealed, encapsulated package. Photonic integrated circuits having grating or edge couplers thereon may be used to wavelength multiplex beams of light emitted by the plurality of laser diodes into a coaxially superimposed aggregate beam. A waveguide medium having one or more directly written waveguides may couple light from laser diodes to a photonic integrated circuit, and may optionally hermetically or partially hermetically seal the laser diodes, eliminating the need for a separate seal. Such optical engines may have advantages over existing designs including, for example, smaller volumes, better manufacturability, faster modulation speed, etc.