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Bending Light with a Tiny Chip

Imagine that you are in a meeting with coworkers or at a gathering of friends. You pull out your cell phone to show a presentation or a video on YouTube. But you don't use the tiny screen; your phone projects a bright, clear image onto a wall or a big screen. Such a technology may be on its way, thanks to a new light-bending silicon chip developed by researchers at Caltech.

The chip eliminates the need for bulky and expensive lenses and bulbs and instead uses an integrated optical phased array to project the image electronically with only a single laser diode as light source and no mechanically moving parts. The technique bypasses traditional optics by manipulating the coherence of light — a property that allows the researchers to "bend" the light waves on the surface of the chip without lenses or the use of any mechanical movement.

As an electronic signal rapidly steers the light beam left, right, up, and down, the light acts as a very fast pen, drawing an image made of light on the projection surface. Because the direction of the light beam is controlled electronically — not mechanically — it can create a sort of line very quickly. Since the light draws many times per second, the eye sees the process as a single image instead of a moving light beam.

Although the chip could easily be incorporated into a cellphone, a tiny projection device can have many applications, including LIDAR used in positioning, robotics, geographical measurements, and mapmaking. Such equipment already exists, but current LIDAR technology requires complex, bulky, and expensive equipment that could be streamlined and simplified to a single chip at a much lower cost.

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