A coupling structure for joining (i) a light guide plate and (ii) a lighting element comprising a mount and a light emitting diode , the coupling structure comprising: - a first reflective region ; - a second reflective region , parallel to and spaced apart from the first reflective region ; - a phosphor region joining the first reflective region and the second reflective region , wherein the phosphor region is positioned between the first reflective region and the second reflective region such that a section of each of first reflective region and the second reflective region extends beyond edges of the phosphor region ; - a first open-ended cavity defined by an inner side of the first reflective region , an inner side of the second reflective region , and a first side of the phosphor region , and configured to be closed by the lighting element , wherein (i) the first reflective region is on a first surface of the lighting element , (ii) the second reflective region is on a second surface of the lighting element , and (iii) the light emitting diode faces the first side of the phosphor region and is separated from it by a space; - a second open-ended cavity located on an opposite side of the phosphor region from the first open-ended cavity, and defined by the inner side of the first reflective region , the inner side of the second reflective region , and a second side of the phosphor region and configured to be closed by a light in-coupling edge of the light guide plate , wherein (i) the first reflective region is on a first surface of the light guide plate and (ii) the second reflective region is on a second surface of the light guide plate ; characterised in that the first reflective region , the second reflective region , and the phosphor region are integrally formed so that the coupling structure is a single piece. - a first reflective region ; - a second reflective region , parallel to and spaced apart from the first reflective region ; - a phosphor region joining the first reflective region and the second reflective region , wherein the phosphor region is positioned between the first reflective region and the second reflective region such that a section of each of first reflective region and the second reflective region extends beyond edges of the phosphor region ; - a first open-ended cavity defined by an inner side of the first reflective region , an inner side of the second reflective region , and a first side of the phosphor region , and configured to be closed by the lighting element , wherein (i) the first reflective region is on a first surface of the lighting element , (ii) the second reflective region is on a second surface of the lighting element , and (iii) the light emitting diode faces the first side of the phosphor region and is separated from it by a space; - a second open-ended cavity located on an opposite side of the phosphor region from the first open-ended cavity, and defined by the inner side of the first reflective region , the inner side of the second reflective region , and a second side of the phosphor region and configured to be closed by a light in-coupling edge of the light guide plate , wherein (i) the first reflective region is on a first surface of the light guide plate and (ii) the second reflective region is on a second surface of the light guide plate ; <EOS>