An optical switch includes a saturable absorber. Coupled to the saturable absorber is an input waveguide, an output waveguide, and a control beam waveguide. In the absence of light input to the control beam waveguide, the saturable absorber prevents an input signal on the input waveguide from passing through and being output on the output waveguide, thus placing the switch in an “off” state. In the presence of light input to the control beam waveguide and incident of the saturable absorber, the saturable absorber allows the input signal to pass through and be output on the output waveguide, thus placing the switch in an “on” state.