Performance of phosphor coated LED optics in ray trace simulations

In commercial high brightness phosphor coated (PC) LED packages the phosphor is put down on the die in the center of the hemispherical encapsulation, representing a quasi-point source that provides convenient optical control in lighting fixture design. However, specific applications may benefit from other package geometries and beam shapes regarding efficiency, color uniformity and thermal management. In order to examine optical arrangements the solid model of an InGaN LED die and the optical system including the phosphor were simulated using Monte-Carlo forward ray tracing technique. Photoluminescence was implemented as two separate processes: short wavelength LED emission and phosphor absorbtion was traced first, followed by re-emission of the down-converted radiation by the phosphor layer, optical properties of existing phosphors were used. Output parameters of the two ray traces were combined and evaluated for the geometries examined.