Tri-band color transmission filter for white LED-based visible light communication

Visible light communication (VLC) based on light emitting diodes has been regarded as an effective complement to radio frequency signal transmission. The color filter in VLC system plays the pivotal role for boosting signal-noise-ratio. In this paper, a tri-band color transmission filter with bandwidths consisting with LED's 30nm is designed based on guided mode resonance, incorporating a sub-wavelength aluminum grating on slab dielectric waveguide made of titanium dioxide on silica substrate. Parameters of grating structure, including the grating period, duty cycle, grating thickness, and waveguide thickness, are optimized by employing particle swarm optimization toolbox. The far field spectrum is calculated by rigorous coupled-wave analysis to verify the effectiveness of the designed filter. Three center-wavelength of transmission bands are 440nm, 530 and 630 nm. The full-width-at-half-maximum (FWHM) bandwidths of three bands are about 30nm which consist with LED's bandwidth.