Integrated waveguide-type red-green-blue beam combiners for compact projection-type displays

We propose and analyze a new integrated waveguide-type red-green-blue (RGB) beam combiner that can contribute to a miniaturization of the compact projection-type displays such as an eyewear projector. The essential point of this beam combiner is that it is composed of three individual waveguides for RGB light inputs, and three directional couplers. The combined output light can be obtained from the single waveguide. The waveguide supports the single mode transmission. The efficiency for output light is as high as 96%, and the size is as small as 0.06×7.8 mm. In addition, the small dependence of the output efficiency on the wavelength and the relatively large fabrication tolerance are obtained.