How to distinguish elastically scattered light from Stokes shifted light for solid-state lighting?
| Abstract | We have studied the transport of light through phosphor diff user platesthat are used in commercial solid-state lighting modules (Fortimo).These polymer plates contain YAG:Ce+3 phosphor particles that bothelastically scatter and Stokes shift light in the visible wavelengthrange (400-700 nm). We excite the phosphor with a narrowband lightsource, and measure spectra of the outgoing light. The Stokes shiftedlight is spectrally separated from the elastically scattered light inthe measured spectra and using this technique we isolate the elastictransmission of the plates. This result allows us to extract thetransport mean free path ltr over the full wavelength range by employingdi ffusion theory. Simultaneously, we determine the absorption mean freepath labs in the wavelength range 400 to 530 nm where YAG:Ce+3 absorbs.The diff use absorption 1/labs spectrum is qualitatively similar to theabsorption coefficient of YAG:Ce+3 in powder, with the diff usespectrum being wider than the absorption coefficient. We propose adesign rule for the solid-state lighting di ffuser plates. |
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| Authors | M. L. Meretska, A. Lagendijk, H. Thyrrestrup, A. P. Mosk, W. L. IJzerman, and W. L. Vos, |
| Year of publication | 2016 |
| Date published | 01/2016 |
| Journal | J. Appl. Phys. |
| Volume | 119 |
| Pages | 093102: 1-9 |
| Keywords | diffusion theory, diffusion with absorption, multiple light scattering, wave propagation in random media |