One such project is called NewsFlash, and uses high-frequency red and green light to transmit data to the built-in camera on a receiving device -- in this case Samsung's Epic 4G.
The other, which faces a specialised type of solar cell made of a material called indium gallium arsenide, is sculpted into a structure called a photonic crystal that causes it to emit infra-red radiation selectively at the frequency best absorbed by the cell.