Energy efficient generation of white light has become an important issue in recent years. Technology of white-light emitting diodes (LEDs) is one of the promising directions. The main challenges in the LED production are understanding scattering, absorption and emission from ab-initio, and obtain chromaticity independent emission directions. Physical understanding of multiple light scattering in the LED can provide us with simple tools for extracting optical parameters of this system.
We have studied the transport of light through phosphor diffuser plates that are used in commercial solid-state lighting modules (Fortimo). These polymer plates contain YAG:Ce+3 phosphor particles that both elastically scatter light and Stokes shift light in the visible wavelength range (400-700 nm). We excite the phosphor with a narrowband light source, and measure spectra of the outgoing light. The Stokes shifted light is spectrally separated from the elastically scattered light in the measured spectra. Using this technique we isolate the elastic transmission of the plates. This result allows us to extract the transport mean free path ltr over the full wavelength range by employing diffusion theory. Simultaneously, we determine the absorption mean free path labs in the wavelength range 400 to 530 nm where YAG:Ce+3 absorbs. The diffuse absorption (µ_a=1/l_abs ) spectrum is qualitative similar to the absorption coefficient of YAG:Ce+3 in powder, with the diffuse spectrum being wider than the absorption coefficient. We propose a design rule for the solid-state lighting diffuser plates.
Maryna L. Meretska, Ad Lagendijk, Henri Thyrrestrup, Allard Mosk, Wilbert IJzerman, and Willem L. Vos, "Diffusion of light in white LEDs (Conference Presentation)," Proc. SPIE 10554, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XXII, 1055404 (Presented at SPIE OPTO: January 29, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2289161.5751488296001.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the conference proceedings. They include the speaker's narration along with a video recording of the presentation slides and animations. Many conference presentations also include full-text papers. Search and browse our growing collection of more than 14,000 conference presentations, including many plenary and keynote presentations.
Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon