Light emitting device

Abstract

A light emitting device () comprising a luminescent element () comprising a first face () and a second face (), the first face comprising a light input surface and one of the first face and the second face comprising a light exit surface, the luminescent element () being adapted for receiving first light () with a first spectral distribution emitted by at least one laser light source () at the light input surface, converting at least a part of the first light with the first spectral distribution to second light () with a second spectral distribution, guiding the second light with the second spectral distribution to the light exit surface and coupling at least a part of the second light with the second spectral distribution out of the light exit surface, and a heat sink element () arranged to be in thermal contact with at least a part of the luminescent element () extending between the first face () and the second face (), wherein the first face () comprises a cross-sectional area A and the luminescent element () further comprises a length L being defined as the shortest distance between the first face and the second face and a characteristic length B of the cross sectional area A, the characteristic length B being defined as the square root of the cross sectional area A, and wherein, and wherein the length L and the characteristic length B of the cross sectional area A are chosen such that they satisfy any one of the relations L/B≥2*E/44(W/mm) for λ<6 W/mK, L/B≥1.3*E/44(W/mm) for 6 W/mK≤λ≤8 W/mK, and L/B≥0.85*E/44(W/mm) for 8 W/mK<λ, where Eis the irradiance of the at least one laser light sources measured in W/mmand λis the thermal heat coefficient of the luminescent element at room temperature.