An example device in accordance with an aspect of the present disclosure includes a ring waveguide and bus waveguide. The ring waveguide has a first coupled portion associated with a first modal index, and the bus waveguide includes a second coupled portion associated with a second modal index. The second coupled portion is evanescently coupleable to the first coupled portion. A laser outcoupling and associated lasing output of the device is variable based on varying a difference between the first modal index and the second modal index to vary coupling between the first coupled portion and the second coupled portion, without varying modal indices of non-coupled portions of the ring waveguide and bus waveguide.