Systems, devices, and methods for providing optical engines and laser projectors that are well-suited for use in wearable heads-up displays (WHUDs) are described. The optical engines of the present disclosure may integrate a plurality of laser diodes (e.g., 3 laser diodes, 4 laser diodes) within a single, hermetically or partially hermetically sealed, encapsulated package. Wavelength stabilization for the laser diodes is achieved by controlling the temperature of the lasers to always be in a particular range of operating specifications which provides wavelength stabilization that meets particular performance criteria. The lasers themselves may be used for temperature control by selectively switching them on to maintain their temperature within a specified range. Alternatively, compact resistive heaters may be positioned proximate the laser diodes to control the temperature of the laser diodes during operation. WHUDs that employ such optical engines and laser projectors are also described. Additionally, optical systems for collimating and shifting light beams are described.