Tuning forks are a classic tool in science classrooms, as a simple strike causes them to produce a pure frequency for a long period of time. This also makes them useful as a reference when sound frequencies are involved, such as when tuning an instrument. Recently researchers at the California Institute of Technology have developed an optical equivalent to a tuning fork, and it is about the size of a quarter.
Optical resonators are not a new technology, but building them with a high quality factor is not very easy. Energy surges in a resonator will cause the frequency of light to fluctuate, and some of these surges are unavoidable due to thermodynamics. However, by creating the longest possible path for the light to travel within the resonator, the surges are dampened. By using an Archimedean spiral, the path, which covers the area of a quarter, is over one meter long; one hundred times longer than previous designs.
This ability to create a stable, pure frequency of light could see use in electronics which have to process optical signals. Given the ever-increasing use of fiber-optic communication, this technology could become very useful as it enables high-performance systems.