Engineering 101

Nano-antennas and Photoluminescence

Will white LEDs lose their light source superiority? Seems so. A 2D photonic crystal or nano-antenna is a structure in which nano-sized particles are arranged periodically on a substrate. With irradiation, combining a nano-antenna with a phosphor plate provides a compelling mix of blue and yellow light.

With white laser diodes, or LD, the blue LDs are highly directional, and the yellow phosphors radiate in all directions for an undesired mixing of colors. Researchers developed phosphor plates combined with nano-antennas using metallic aluminum, enabling increased photoluminescence. Aluminum nanoparticles scatter light and improve light intensity and directionality, but it also absorbs light, reducing the output. This was a significant bottleneck, especially in high-intensity lighting applications. Researchers at Kyoto University just achieved a ten-fold enhancement of forward-directed photoluminescence by replacing aluminum with a better material.

Titanium dioxide is best for its high refractive index and low-light absorption. Although the light-scattering intensity of titanium oxide first appeared inferior to metallic aluminum, the team used computer simulations to devise the optimal nano-antenna design.

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