Steering Light with Chips
Most lights utilize a shroud of one kind or another to direct the emitted photons in one way or another, but that is not the only way to aim light. One can take advantage of the wave nature of light and use interference to cancel out the light in all but the desired direction. Researchers at MIT have recently created two of these phase arrays on chips that could lead to advanced photonic devices including holographic TVs.
Phase is a property of all light and concerns how the peaks and troughs in its waveform align. When the phases align, light waves amplify each other, but when their phases are reversed, they may cancel each other out. This is what the researchers are taking advantage of on the chips by tuning on-chip antennas to emit light with specific phases. For one chip with 4096 antennas in a 64x64 grid, the antennas are fixed to generate the MIT logo from laser light. The other chip only has 64 antennae on it in an 8x8 grid, but these antennae are tunable so they may light emit long-distance light in any direction. Within a certain range of the chips the light waves have not yet interfered and one can see every antenna is emitting light.
Potentially this ability to direct light by tuning antennas on a chip could be used to create holographic televisions, advanced medical-imaging devices, and more. The true potential of this technology will be realized though when it has been integrated into a silicon chip, instead of requiring discrete wires for each tunable antenna.