Increasing Semiconductors' Optical Range
Right now there is considerably more photons passing through us than we can see, because the receptors in our eyes only respond to a small portion of the electromagnetic spectrum. Semiconductors likewise only react to light of certain frequencies, which can be frustrating when you want to detect more light than is in that range. Researchers at Georgia State University have found a way to tune those frequencies though, which could open up many possibilities.
Electrons, like many objects, need so much energy to start moving. In a conductor the required energy is very, very low while in an insulator it is very high. Semiconductors are somewhere in the middle, so when a photon strikes a semiconductor, it has to impart enough energy to get an electron moving to create a detectible current. This means detecting photons of lower frequencies and energy typically requires special semiconductors, but the Georgia researchers have found a way around this. Instead of changing the semiconductor, the researchers have added another light source. This extra light primes the semiconductor with enough energy so that even a lower energy photon can kick an electron, and create a current.
The device the researchers built was able to detect photons with wavelengths as great as 55 micrometers, which is significantly longer than the 4 micrometers the device would normally detect. Potentially this technique could be used for advanced sensors that can detect certain gases as well as building solar panels that absorb more of the spectrum.
Source: Georgia State University