An optical resonator is provided, and methods for making the same, as well as devices and sub-assemblies including the same. For example, such an electronic device (FIG. 4) may include a first electronic component (172) designed to be photoactive to radiation having a first wavelength and a second electronic component (174) designed to be photoactive to radiation having a second wavelength. The device may also include a cavity that defines an optical resonator having a cavity length such that the optical resonator resonates in successive resonant modes that locate at the first and second wavelengths.