"(ScienceDaily May 21, 2012) - It may not be intuitive, but a coating of reflective metal can actually make something less visible, engineers at Stanford and UPenn have shown. They have created an invisible, light-detecting device that can "see without being seen."At the heart of the device are silicon nanowires covered by a thin cap of gold. By adjusting the ratio of metal to silicon -- a technique the engineers refer to as tuning the geometries -- they capitalize on favorable nanoscale physics in which the reflected light from the two materials cancel each other to make the device invisible.Pengyu Fan is the lead author of a paper demonstrating the new device published online May 20th in the journal Nature Photonics. He is a doctoral candidate in materials science and engineering at Stanford University working in Professor Mark Brongersma's group. Brongersma is senior author of the study.Cloak of invisiblityLight detection is well known and relatively simple. Silicon generates electrical current when illuminated and is common in solar panels and light sensors today. The Stanford device, however, is a departure in that for the first time it uses a relatively new concept known as plasmonic cloaking to render the device invisible. . ." |
