Concepts of the present disclosure may be employed to optimize optical pumping and ensure high modal gain in the active region of an optically pumped laser source by establishing an optical coupling gap such that the pump waveguide mode field overlaps the active gain region associated with the signal waveguide. The optical coupling gap is tailored to be sufficiently large to ensure that a significant active gain region length is required for absorption and sufficiently small to ensure that the pump waveguide mode field P overlaps the active gain region. In accordance with one embodiment of the present disclosure, the pump waveguide core is displaced from the signal waveguide core by an optical coupling gap g in a lateral direction that is approximately perpendicular to the optical pumping axis. A decayed intensity portion of the pump waveguide mode field extends into the active gain region to optically pump the active gain region and form an optical signal propagating along the longitudinal optical signal axis of the signal waveguide core.