Photodetector Created for Polarized Light
Much of the light we see is made up of unaligned waves that impact our eyes at every angle, but some light is polarized, so all of the waves are aligned in one direction. Human eyes cannot distinguish polarized light, nor can most devices, so when an application calls for it, a grating will be placed in front of a detector. Researchers at Rice University and Sandia National Laboratories though have created a broadband photodetector with the intrinsic ability to discern polarized light using carpets of nanotubes.
Carbon nanotubes are tubes just nanometers wide, but can be quite long and semiconducting, causing them to interact with only specific frequencies of light. Normally when they are produced, the nanotubes will be of different lengths and aligned in different directions, but the researchers found a way to use Teflon film to flatten them into carpets aligned in one direction. This alignment causes the nanotubes to only detect light polarized in the same direction, and the variety of lengths allows them to interact with a range of frequencies.
To actually turn the nanotube-carpet into a photodetector, the researchers had to dope the carpets to be positively and negatively charged. By overlapping the different carpets, a p-n junction is formed, like those found throughout microelectronics.
Source: Rice University