An optical apparatus comprising: a silicon [claim 14] semiconductor substrate (102, 402); a germanium-silicon layer (106, 406) coupled to the semiconductor substrate, the germanium-silicon layer including an optical sensor [p. 8, 1. 28-29] region [claim 1] configured to absorb photons (112, 412) and to generate photo-carriers from the absorbed photons, wherein a composition of the germanium-silicon layer differs from a composition of the semiconductor substrate; one or more first switches (108, 110, 408, 410) controlled by a first control signal (122, 132, 422, 432), 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 (108, 110, 408, 410) controlled by a second control signal (122, 132, 422, 432), 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, wherein the one or more first switches comprise: a first p-doped region (128, 138, 428, 438) in the germanium-silicon layer, wherein the first p-doped region is controlled by the first control signal; and a first n-doped region (126, 136, 426, 436) in either the germanium-silicon layer or the semiconductor substrate, wherein the first n-doped region is coupled to a first readout integrated circuit (124, 134, 424, 434); wherein the one or more second switches comprise: a second p-doped region (128, 138, 428, 438) in the germanium-silicon layer, wherein the second p-doped region is controlled by the second control signal; and a second n-doped region (126, 133, 426, 436) in either the germanium-silicon layer or the semiconductor substrate, wherein the second n-doped region is coupled to a second readout integrated circuit (124, 134, 424, 434). a silicon [claim 14] semiconductor substrate (102, 402); a germanium-silicon layer (106, 406) coupled to the semiconductor substrate, the germanium-silicon layer including an optical sensor [p. 8, 1. 28-29] region [claim 1] configured to absorb photons (112, 412) and to generate photo-carriers from the absorbed photons, wherein a composition of the germanium-silicon layer differs from a composition of the semiconductor substrate; one or more first switches (108, 110, 408, 410) controlled by a first control signal (122, 132, 422, 432), 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 (108, 110, 408, 410) controlled by a second control signal (122, 132, 422, 432), 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, wherein the one or more first switches comprise: a first p-doped region (128, 138, 428, 438) in the germanium-silicon layer, wherein the first p-doped region is controlled by the first control signal; and a first n-doped region (126, 136, 426, 436) in either the germanium-silicon layer or the semiconductor substrate, wherein the first n-doped region is coupled to a first readout integrated circuit (124, 134, 424, 434); a first p-doped region (128, 138, 428, 438) in the germanium-silicon layer, wherein the first p-doped region is controlled by the first control signal; and a first n-doped region (126, 136, 426, 436) in either the germanium-silicon layer or the semiconductor substrate, wherein the first n-doped region is coupled to a first readout integrated circuit (124, 134, 424, 434); wherein the one or more second switches comprise: a second p-doped region (128, 138, 428, 438) in the germanium-silicon layer, wherein the second p-doped region is controlled by the second control signal; and a second n-doped region (126, 133, 426, 436) in either the germanium-silicon layer or the semiconductor substrate, wherein the second n-doped region is coupled to a second readout integrated circuit (124, 134, 424, 434). a second p-doped region (128, 138, 428, 438) in the germanium-silicon layer, wherein the second p-doped region is controlled by the second control signal; and a second n-doped region (126, 133, 426, 436) in either the germanium-silicon layer or the semiconductor substrate, wherein the second n-doped region is coupled to a second readout integrated circuit (124, 134, 424, 434).