An optical apparatus including a semiconductor substrate; a first light absorption region supported by the semiconductor substrate, the first light absorption region including germanium and configured to absorb photons and to generate photo-carriers from the absorbed photons; a first layer supported by at least a portion of the semiconductor substrate and the first light absorption region, the first layer being different from the first light absorption region; one or more first switches controlled by a first control signal, the one or more first switches configured to collect at least a portion of the photo-carriers based on the first control signal; and one or more second switches controlled by a second control signal, the one or more second switches configured to collect at least a portion of the photo-carriers based on the second control signal, wherein the second control signal is different from the first control signal.