A reflector chamber, used to couple a light source to a downstream
light-transport medium, includes a forward reflector which folds the
light impinging upon it forward and a backward reflector that folds
backwards the light received from the light source or the forward
reflector. The two reflectors are judiciously shaped so as to maximize
the energy density at the output aperture with an angle of emission
within the numerical aperture of the downstream medium. The forward
reflector is preferably shaped substantially flat and coplanar with the
light source. The backward reflector is preferably a concave section. A
diverging light reflector may be added to the output aperture of the
coupler in order to increase its efficiency.