A colour conversion resonator system (400, 500, 600, 700, 1000, 1100), comprising: a first partially reflective region configured to transmit light of a first primary peak wavelength and to reflect light of a second primary peak wavelength; a second partially reflective region configured to at least partially transmit light of the first and second primary peak wavelengths and to reflect light of a third primary peak wavelength; a third partially reflective region configured to at least partially reflect light with the third primary peak wavelength; a first colour conversion resonator cavity arranged to receive input light with the first primary peak wavelength through the first partially reflective region and to convert at least some of the light of the first primary peak wavelength to provide light of the second primary peak wavelength, wherein the first colour conversion resonator cavity is arranged such that the second primary peak wavelength resonates in the first colour conversion resonator cavity and resonant light with the second primary peak wavelength is output through the second partially reflective region; and a second colour conversion resonator cavity arranged to receive input light comprising the second primary peak wavelength through the second partially reflective region and to convert at least some of the second primary peak wavelength to provide light of the third primary peak wavelength, wherein the second colour conversion resonator cavity is arranged such that the third primary peak wavelength resonates in the second colour conversion resonator cavity and resonant light with the third primary peak wavelength is output through the third partially reflective region, wherein the first colour conversion resonator cavity and the second resonator cavity are arranged partially to overlap to provide a non-overlapping portion and an overlapping portion thereby to define a first light emitting surface and a second light emitting surface respectively, wherein the first light emitting surface is arranged to provide resonant light of the second primary peak wavelength and the second light emitting surface is arranged to provide resonant light of the third primary peak wavelength. a first partially reflective region configured to transmit light of a first primary peak wavelength and to reflect light of a second primary peak wavelength; a second partially reflective region configured to at least partially transmit light of the first and second primary peak wavelengths and to reflect light of a third primary peak wavelength; a third partially reflective region configured to at least partially reflect light with the third primary peak wavelength; a first colour conversion resonator cavity arranged to receive input light with the first primary peak wavelength through the first partially reflective region and to convert at least some of the light of the first primary peak wavelength to provide light of the second primary peak wavelength, wherein the first colour conversion resonator cavity is arranged such that the second primary peak wavelength resonates in the first colour conversion resonator cavity and resonant light with the second primary peak wavelength is output through the second partially reflective region; and a second colour conversion resonator cavity arranged to receive input light comprising the second primary peak wavelength through the second partially reflective region and to convert at least some of the second primary peak wavelength to provide light of the third primary peak wavelength, wherein the second colour conversion resonator cavity is arranged such that the third primary peak wavelength resonates in the second colour conversion resonator cavity and resonant light with the third primary peak wavelength is output through the third partially reflective region, wherein the first colour conversion resonator cavity and the second resonator cavity are arranged partially to overlap to provide a non-overlapping portion and an overlapping portion thereby to define a first light emitting surface and a second light emitting surface respectively, wherein the first light emitting surface is arranged to provide resonant light of the second primary peak wavelength and the second light emitting surface is arranged to provide resonant light of the third primary peak wavelength.