In one form or another, we are likely familiar with projectors. These devices deliver images on a screen by passing light through an image and lenses, which requires a somewhat large system. Researchers at Caltech though have created a single, millimeter-square chip that could one day be used to project images inexpensively.
This chip works by shifting the phase of light waves. Waves in phase will amplify each other, while those exactly out of phase will cancel out. Between those extremes though, the waves can be made to turn in one direction or another, and that is what the chip is taking advantage of to direct the light anywhere on a screen very rapidly. In fact the light beam is being moved so quickly that the human eye will see an image, instead of a beam tracing out the image.
So far the researchers have been working with silicon, which operates best with infrared light, but could move to other semiconductors that operate on visible light. With such technology it may be possible to build very small projectors into smartphones at very low cost, but at such a low cost and small size, these projectors could see many, many more applications.