Some implementations of the disclosure relate to an optical system, including: a first light source; a secondary light source that is optically coupled to the first light source; a reflective element that is transparent with respect to the first light source but reflective with respect to the secondary light source, the reflective element being disposed between the first light source and the secondary light source; and a semi-reflective layer disposed on the secondary light source, such that reflection of light from the secondary light source by the reflective element and back through the semi-reflective element results in greater than 25% of the light from first light source exiting the optical system.