Laser-line-driven phosphor-converted extended white light source with uniform illumination.

Abstract

We report the development of laser-driven extended white light source designed as a light sheet for general illumination. This light sheet is made of two large diffused glass plates. A Ce:YAG phosphor layer was coated and sandwiched between the two diffusing sheets. The blue laser beam was first converted into a uniform laser line using a cylindrical lens, and a laser line was made incident parallel to the edges of the designed light sheet. The blue photons are waveguided inside the glass sheet via total internal reflection and scattered from the diffused surface. Some of the blue photons are absorbed by the Ce:YAG phosphor and down-converted into yellow light of longer wavelength. The white light emanating from the diffuse surface is the combined effect of yellow light with original blue light. The developed light sheet with the combination of laser line generation and total internal reflection is a unique and low-cost method for generating white light with uniform illumination. The details of the development of the light sheet and laser line generation are described. The experimental parameters, such as correlated color temperature and color coordinates, are reported.