The invention relates to an illuminating device (1) comprising a substrate (2), a non-transparent spacer (4) which is connected to the substrate (2) so as to be hermetically sealed, an opening in the spacer (4), opposite said substrate (2), and an illumination element (3) positioned beneath the spacer (4) and beneath the opening, which element is connected to the substrate (2) so as to be hermetically sealed, characterized in that the opening in the spacer (4) is closed, so as to be hermetically sealed, by an optical element (5) consisting of a glass material the volume of which comprises at least one luminophore and thus constitutes a luminescent composite glass material.