A lighting device comprising: - one or more light sources configured to provide light source light ; - a luminescent element comprising an elongated light transmissive body having a first face and a second face defining a length (L) of the light transmissive body , the light transmissive body comprising one or more radiation input faces and a first radiation exit window , wherein the second face comprises the first radiation exit window ; the elongated light transmissive body comprising a luminescent material configured to convert at least part of light source light received at one or more radiation input faces into luminescent material light , and the luminescent element configured to couple at least part of the luminescent material light out at the first radiation exit window as converter light ; wherein the light transmissive body has a first index of refraction n1; - a beam shaping optical element optically coupled with the first radiation exit window , the beam shaping optical element comprising a radiation entrance window configured to receive at least part of the converter light ; wherein the beam shaping optical element has a second index of refraction n2; wherein: - 0.75≤n1/n2≤1.25; - an optical connector configured between the elongated light transmissive body and the beam shaping optical element , characterized by the optical connector comprising a glass material , wherein the glass material has acomposition selected from a range defined in the ternary B 2 O 3 -Bi 2 O 3 -ZnO diagram by the following compositions indicating the quadrilateral corner points of the range: mol% B 2 O 3 mol% Bi 2 O 3 mol% ZnO 25 mol% 7.5 mol% 67.5 mol% 80 mol% 20 mol% 0 mol% 65 mol% 35 mol% 0 mol% 22.5 mol% 20 mol% 57.5 mol% - wherein the beam shaping optical element comprises an optical element material different from the glass material , - and wherein the optical connector comprises a glass frit connection . - one or more light sources configured to provide light source light ; - a luminescent element comprising an elongated light transmissive body having a first face and a second face defining a length (L) of the light transmissive body , the light transmissive body comprising one or more radiation input faces and a first radiation exit window , wherein the second face comprises the first radiation exit window ; the elongated light transmissive body comprising a luminescent material configured to convert at least part of light source light received at one or more radiation input faces into luminescent material light , and the luminescent element configured to couple at least part of the luminescent material light out at the first radiation exit window as converter light ; wherein the light transmissive body has a first index of refraction n1; - a beam shaping optical element optically coupled with the first radiation exit window , the beam shaping optical element comprising a radiation entrance window configured to receive at least part of the converter light ; wherein the beam shaping optical element has a second index of refraction n2; - 0.75≤n1/n2≤1.25; - an optical connector configured between the elongated light transmissive body and the beam shaping optical element , characterized by the optical connector comprising a glass material , wherein the glass material has acomposition selected from a range defined in the ternary B 2 O 3 -Bi 2 O 3 -ZnO diagram by the following compositions indicating the quadrilateral corner points of the range: mol% B 2 O 3 mol% Bi 2 O 3 mol% ZnO 25 mol% 7.5 mol% 67.5 mol% 80 mol% 20 mol% 0 mol% 65 mol% 35 mol% 0 mol% 22.5 mol% 20 mol% 57.5 mol% - wherein the beam shaping optical element comprises an optical element material different from the glass material , - and wherein the optical connector comprises a glass frit connection . <EOS>