Abstract

To obtain high reflectivity over a broad range of green, yellow, and red light as well as blue light incidents from a particular angular range and further increase the luminous efficiency of a phosphor-converted white LED packaging module, a novel back hybrid reflector including a ${\mathrm{SiO}}_2$ total internal reflection layer (TIR), five-pair ${\mathrm{SiO}}_2/{\mathrm{TiO}}_2$ double distributed Bragg reflector (DBR) stacks, and a gold (Au) metallic mirror was designed and fabricated. The double DBR stacks have layers configured to reflect green, yellow, and red light as well as blue light, which includes a first portion where the thickness of the layers are relatively larger, and also includes a second portion where the thickness of the layers is relatively smaller. Light that is passing toward the hybrid reflector at angles greater than the critical angle (56°) is reflected by the ${\mathrm{SiO}}_2$ TIR layer at the $\text{sapphire}/{\mathrm{SiO}}_2$ interface, whereas the light that passes through the ${\mathrm{SiO}}_2$ TIR layer with incident angles between 0° and 56° is reflected by the double DBR stacks. The overall hybrid reflector can ensure a reflectivity of more than 95% in both the blue light wavelength region and the yellow light wavelength region. The obtained higher reflectivity in the yellow light wavelength region will benefit the phosphor-converted LEDs because yellow light backscattered by phosphor particles is reflected upward.

© 2014 Optical Society of America

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