An optical device includes a light source with at least two radiation sources, and at least two layers of wavelength-modifying materials excited by the radiation sources that emit radiation in at least two predetermined wavelengths. Embodiments include a first plurality of n radiation sources configured to emit radiation at a first wavelength. The first plurality of radiation sources are in proximity to a second plurality of m of radiation sources configured to emit radiation at a second wavelength, the second wavelength being shorter than the first wavelength. The ratio between m and n is predetermined. The disclosed optical device also comprises at least two wavelength converting layers such that a first wavelength converting layer is configured to absorb a portion of radiation emitted by the second radiation sources, and a second wavelength converting layer configured to absorb a portion of radiation emitted by the second radiation sources.