New Device to Focus Light
The common photon is an amazing quantum of electromagnetic energy as it not only carries information such as color but also exists as both a particle and a wave, all while traveling at the speed of light. These properties make it of keen interest to researchers everywhere who are trying to push past the boundaries of traditional electronics. Recently researchers at the California Institute of Technology have created a device that pushes past one of light's own boundaries; the diffraction limit.
Just as a guitar string's length determines the pitch it produces, the wavelength of light determines how small a space it can fit in, and that limit is known as the diffraction limit. For visible light it is in the hundreds of nanometers, which is too large to work with many examples of modern electronics. To reach even smaller sizes researchers, including those at Caltech, are turning to plasmonics, which couple photons and electrons so the information of the light signal can fit within the much smaller size of an electron. To that end the Caltech researchers designed a device that looks like a rectangle of silicon dioxide that tapers down to a point, all coated in gold. When light enters the larger end it couples with electrons and focuses down through the taper, where it is emitted.
Similar nanofocusing devices have been made before, but none have achieved the efficiency of this design which preserves half the light's original energy, when it is focused to a point just a few nanometers wide. Making the point larger increases the efficiency. Potentially this technology could be used not only to increase the data throughput of a fiber optic cable but also increase the density of hard drives from 1 terabyte per square inch to 50 TB/in2.