Nearly all electronics require oscillators that create precise frequencies, which have, until now, relied upon quartz crystals to provide a frequency reference, like a tuning fork used to tune a piano. However, future high-end electronics will require references beyond the performance of quartz, say scientists at California Institute of Technology, Pasadena.

The new laser frequency reference (left) is a small 6 mm disk; the quartz “tuning fork” (middle) is the frequency reference commonly used today in wristwatches to set the second. The dime (right) is for scale. (Credit: Jiang Li/Caltech)

They have developed a method to stabilize microwave signals in the range of gigahertz using a pair of laser beams as the reference, instead of a crystal.

Quartz crystals “tune” oscillators by vibrating at relatively low frequencies. The new technique, called electro-optical frequency division, reverses the architecture used in standard crystal-stabilized microwave oscillators by using optical signals with much higher frequency than the microwave signal to be stabilized, they say.

Electrical frequency dividers used widely in electronics can work at frequencies no higher than 50 to 100 GHz. Their new architecture, they say, stabilizes a common microwave electrical oscillator with optical references in the range of terahertz or trillions of cycles per second.

The optical reference used by the researchers is a laser that appears as a tiny disk. At only 6 mm in diameter, the device is very small, making it particularly useful in compact photonics devices, electronic-like devices powered by photons instead of electrons.