Caltech researchers develop light-bending silicon chip
13 Mar 2014
A new light-bending, silicon chip developed by researchers at California Institute of Technology (Caltech) acts as a lens-free projector and could one day end up in your cell phone. Thanks to the new chip, the need for bulky and expensive lenses and bulbs as used in traditional projectors is eliminated.
According to Ali Hajimiri, Thomas G Myers professor of electrical engineering at Caltech, the chip used a so-called integrated optical phased array (OPA) to project the image electronically using only a single laser diode as light source without any mechanical moving parts, IANS reported.
The advantage of the technology was that the chips being small can be made at a very low cost, while opening up lots of interesting possibilities. Hajimiri and his assistants bypassed traditional optics by manipulating the coherence of light – a property that allowed researchers to 'bend' the light waves on the surface of the chip without the use of lenses or any mechanical movement.
In traditional projectors-like those used to project a film or classroom lecture notes, a beam of light is passed through a tiny image, using lenses to map each point of the small picture to corresponding, yet expanded, points on a large screen.
If two waves are coherent in the direction of propagation-meaning that the peaks and troughs of one wave aligned exactly with those of the second wave-the waves combined, resulting in a single wave, a beam having twice the amplitude and four times the energy of the initial wave, moving in the direction of the coherent waves.
Hajimiri said, by changing the relative timing of the waves, one could change the direction of the light beam.
He added, if 10 people kneeling in line by a swimming pool were to dive into the water at the exact same instant, they would make one big wave that travelled directly away from them. However, if 10 separate slaps were staggered-each person hitting the water a half a second after the last-there would still be one big, combined wave, but with the wave bending to travel at an angle, he said, according to www.caltech.edu.
Using a series of pipes for the light-called phase shifters-the OPA chip similarly slowed down or speeded up the timing of the waves, to control the direction of the light beam.
