The system includes a light-transmitting medium positioned on a base. The light-transmitting medium included a ridge and a slab region. The ridge extends upward from the slab region and defines a portion of a waveguide on the base. The waveguide is configured to guide a light signal through the device. The device also includes an avalanche effect light sensor positioned on the base and configured to detect the presence of the light signal. The light sensor includes a light-absorbing medium positioned on the ridge of the light-transmitting medium such that the light signal is coupled from the light-transmitting medium into the light-absorbing medium. The light-transmitting includes a charge layer located at an interface of the light-transmitting medium and the light-absorbing medium. A multiplication region is formed in the slab regions of the light-transmitting medium such that the multiplication region receives charge carriers from the charge layer during the operation of the light sensor.