Light scattering on dusty plasmas: How to improve the quality of white LEDs?

The market share of Light Emitting Diodes (LEDs) in the lighting world is growing quickly (4% in 2013 to an expected 74% in 2030), mainly due to the high energy efficiency compared with traditional lamps. However, the white light which is produced by LEDs does not have the same color temperature as is produced by (for example) incandescent lamps which are perfect black body radiators. Blue light from the LED propagates through a slab of scattering material, where phosphor particles convert the light to different wavelengths, composing white light. To study the extremely complex scatter process inside this phosphor layer, a cloud of dust particles being confined inside a plasma is used as a dynamic scatter sample. When macroscopic dust particles are immersed in a discharge, they acquire a negative charge due to the significant difference in mobility between electrons and ions. Due to this negative charge, dust particles are being confined by the electrostatic field in the plasma sheath at the border of the discharge. By changing the plasma parameters, particle cloud properties like density and configuration can be controlled carefully. Light scattering on dust particles is commonly used to study the behavior of dusty plasmas. In this research however, a dusty plasma is used as a tool to study scattering of light. The unique advantage of this technique is that properties of the sample can be changed I) in-situ and II) by just “turning a knob”. A sophisticated setup is designed and developed, allowing spectroscopic measurements at 360° around the dust cloud. Presented will be the first obtained results from this setup concerning the energy density of the.