An optical assembly comprises a combination of semiconductor optical gain elements, microlenses, and a wavelength-selective planar lightwave circuit (PLC) that routes light of different wavelengths from a different inputs to a single output. The microlenses couple light from the semiconductor optical gain elements into the PLC. The positions of the microlenses can be adjusted using micromechanical holders that are part of their carriers, and are free to move initially, and fixed in place after optimization of the optical coupling. In operation, the gain elements are activated simultaneously, with one wavelength of light lasing within each gain element. All output wavelengths of light exit from a single output of the PLC in a single spatial mode.