An eye-tracking system includes an at least partially transparent visible light waveguide having a visible light display region configured to emit visible light to an eye of a user. A light source is configured to emit at least infrared (IR) light that travels along an IR light path to the eye of the user. A microelectromechanical system (MEMS) projector positioned in the IR light path directs the IR light. At least one diffractive input coupler on an input end of the IR light path downstream of the MEMS projector diffracts at least a portion of the IR light. At least one diffractive output coupler positioned in the IR light path downstream of the diffractive input coupler receives the IR light and directs the IR light toward the eye. At least one sensor is configured to receive the IR light after being reflected by the eye.