Interplay between multiple scattering, emission, and absorption of light in the phosphor of a white light-emitting diode.

We study light transport in phosphor plates of white light-emitting diodes (LEDs). We measure the broadband diffuse transmission through phosphor plates of varying YAG:Ce(3+) density. We distinguish the spectral ranges where absorption, scattering, and re-emission dominate. Using diffusion theory, we derive the transport and absorption mean free paths from first principles. We find that both transport and absorption mean free paths are on the order of the plate thickness. This means that phosphors in commercial LEDs operate well within an intriguing albedo range around 0.7. We discuss how salient parameters that can be derived from first principles control the optical properties of a white LED.

Stimulated Raman gain scattering in planar dielectric waveguides.

We have measured the vibrational Raman spectrum of a 1.2-microm-thick polystyrene film by using this film as an optical waveguide in a waveguide-stimulated Raman gain experiment. A gain factor of 1.3% was measured for the strong benzene mode at 1002 cm(-1). This value is in reasonable agreement with theoretical predictions.