Light generating system comprising an elongated luminescent body

Abstract

The invention provides an elongated luminescent body () comprising an elongated support () and a coating layer (), wherein the elongated luminescent body () further comprises a body axis (BA), and a length parameter P of a body dimension perpendicular to the body axis (BA), wherein the length parameter P is selected from height (H), width (W) and diameter (D), wherein: —the elongated support () comprises a support material (), a support material index of refraction n1, wherein the support material index of refraction n1 is at least 1.4, a support surface (), and a support length (L); —the coating layer () is configured on at least part of the support surface () over at least part of the support length (L), wherein the coating layer () comprises a coating layer material (), a coating layer index of refraction n2, wherein coating layer index of refraction n2 is at least 1.4, and a coating layer thickness (d), wherein the coating layer material () has a composition different from the support material (), wherein the coating layer material () comprises a luminescent material () configured to absorb one or more of UV radiation and visible light, and to convert into luminescent material light () having one or more wavelengths in one or more of the visible and the infrared; and —the support material () is transmissive for the luminescent material light (), and (i) −0.2≤n1−n2≤0.2 and (ii) d/P≤0.25 apply.