System Bits: Sept. 16

Increasing optical storage capacity with holograms
Researchers from the University of Cambridge have developed a new method for making multi-colored holograms from a thin film of silver nanoparticles, which they say could greatly increase the storage capabilities of typical optical storage devices.

The interference produced by the interaction of light with the nanoparticles allows the holograms to go beyond the normal limits of diffraction, or the way in which waves spread or bend when they encounter an opening or obstacle.

When metallic particles have dimensions on the nanoscale, they display iridescent colours. A noted example of this phenomenon is the Lycurgus cup, which was made in the 4th century during the Roman Empire, and changes color when held up to the light. An optical phenomenon, known as dichroism, occurs when the color of the cup changes from green to red according to the position of the light source.

Roman artisans made the cup by incorporating nanoparticles into glass, although they would have been unaware of the specific physical characteristics responsible for the colors observed in the cup. Only in the last 20 years have scientists begun to understand this phenomenon, but they have not been able to utilize its effects in currently-available technology.

To apply this phenomenon in modern optics, an interdisciplinary team of researchers have created nanoscale metallic nanoparticle arrays that mimic the color effects of the Lycurgus cup, to form multi-color holograms. This breakthrough could lead to the shrinkage of standard bulky optical devices.

Preventing glare, improving vision
A smart headlight developed at Carnegie Mellon University’s Robotics Institute enables drivers to take full advantage of their high beams without fear of blinding oncoming drivers or suffering from the glare that can occur when driving in snow or rain at night.

The programmable headlight senses and tracks virtually any number of oncoming drivers, blacking out only the small parts of the headlight beam that would otherwise shine into their eyes. During snow or rain showers, the headlight improves driver vision by tracking individual flakes and drops in the immediate vicinity of the car and blocking the narrow slivers of headlight beam that would otherwise illuminate the precipitation and reflect back into the driver’s eyes.

The programmable headlight senses and tracks virtually any number of oncoming drivers, blacking out only the small parts of the headlight beam that would otherwise shine into their eyes. (Source: Carnegie Mellon University)

The research team assembled their experimental system from off-the-shelf parts and mounted the system atop the hood of a pickup truck, serving as the equivalent of a third headlight during street tests. (Source: Carnegie Mellon University)