  Lighting is a crucial technology that is used every day. The introduction of
the white light emitting diode (LED) that consists of a blue LED combined with
a phosphor layer, greatly reduces the energy consumption for lighting. Despite
the fast-growing market white LED's are still designed using slow, numerical,
trial-and-error algorithms. Here we introduce a radically new design principle
that is based on an analytical model instead of a numerical approach. Our
design model predicts the color point for any combination of design parameters.
In addition the model provides the reflection and transmission coefficients -
as well as the energy density distribution inside the LED - of the scattered
and re-emitted light intensities. To validate our model we performed extensive
experiments on an emblematic white LED and found excellent agreement. Our model
provides for a fast and efficient design, resulting in reduction of both design
and production costs.
