University of Twente physicists have have shown how to find open channels for light in opaque material by using constructive interference to control the shape of incoming light waves.

They focused a laser beam onto an opaque layer of granular zinc oxide and used a digital camera to measure the light emerging from the other side. The researchers then used signals from the camera to control the shape of the incoming wave through a computerized feedback loop. A liquid crystal display shaped the wave by delaying single segments of the laser beam independently. By optimizing these delays, the researchers boosted the light reaching the camera by as much as 44% over the initial unshaped case. They calculated that a maximum transmission of two-thirds of the incoming light is possible.

Being able to enhance the light transmission through scattering materials could have potential applications in biological imaging and therapy, as well as improving cellular phone reception among tall buildings.