Light converting device having a wavelength converting layer with a hydrophobic nanostructure

A light converting device comprising:

• a solid state light source;
• a wavelength converting layer arranged to at least partly wavelength convert the light emitted by the solid state light source, the wavelength converting layer having a back side facing the solid state light source and a front side opposite the backside, wherein the front side of the wavelength converting layer defines an exit window of the light converting device;
• wherein the light converting device further comprises a hydrophobic nanostructure having spaced apart protrusions, the protrusions being provided on the front side of the wavelength converting layer, and having a height (D) above the front side of the wavelength converting layer,
• wherein an air layer is positioned above the front side of the wavelength converting layer, extending along the height of the protrusions,
• wherein the height (D) of the spaced apart protrusions is selected to be larger than the penetration (dp) into the hydrophobic nanostructure of an evanescent wave of light being totally internally reflected at a junction of the front side of the wavelength converting layer and the air layer, and
• wherein the light converting device further comprising a protective coating applied on top of the hydrophobic nanostructure.