Wavelength converting element

\u3cp\u3eA wavelength converting element (101, 102, 103, 110) comprising a polymeric carrier material comprising a first wavelength converting material adapted to convert light of a first wavelength to light of a second wavelength, wherein the oxygen diffusion coefficient (D) of the polymeric carrier material is 8 x 10-13 cm2/s or less at 25°C. A prolonged lifetime of the wavelength converting material is achieved by selecting a polymeric carrier material with an oxygen diffusion coefficient (D) at 8x10-13 cm2/s or less at 25°C.\u3c/p\u3