There is provided a light source arranged to output light at a first wavelength. The light source comprises a luminescent concentrator having a slab-shaped geometry. The luminescent concentrator comprises: an input port arranged to receive light and define a first area an output port arranged to transmit light and define a second area which is smaller than the first area and surfaces arranged to direct light inside the luminescent concentrator to the output port. The luminescent concentrator further comprises lumophores arranged to receive light at a second wavelength and emit light at the first wavelength and a pump light supply coupled to the input port and arranged to illuminate the input port with light at the second wavelength.
