Researchers in the United States have developed a technique that uses lasers – which produce more precise oscillators than those based on quartz crystals – capable of boosting the performance of electronic equipment.
Quartz crystals, which are components of all our everyday electronic devices, ‘tune’ oscillators by vibrating at relatively low frequencies in response to electrical stimulation. Oscillator frequency precision is essential both for digital electronics and analogue devices such as clocks and meters. Ever since quartz was first used for this purpose, it has always seemed the most reliable material for oscillators. However, this view looks set to change following the development by US-based researchers of a method to stabilise microwave signals in the range of gigahertz, i.e. billions of cycles per second, using a pair of laser beams as the reference in lieu of a crystal. Theoretically the lasers, using optical signals much higher in frequency than the microwave signal to be stabilised, will produce a better reference than quartz.
Lasers provide greater precision
The research is being carried out by a team led by Kerry Vahala, Professor of Information Science and Technology and Applied Physics at the California Institute of Technology (Caltech). “Our new method reverses the architecture used in standard crystal-stabilised microwave oscillators; the 'quartz' reference is replaced by optical signals much higher in frequency than the microwave signal to be stabilised,” explains Vahala. According to the Caltech research team, the new technique uses a hybrid architecture, which Vahala and his colleagues have dubbed ‘electro-optical frequency division’ – a combination of electronics and fibre optics – which enables references at much higher frequencies, in the range of terahertz, i.e. trillions of cycles per second. The technique involves using a pair of laser beams very close together to generate what is known as a ‘comb’ of regular and equidistant frequencies which allows the formation of stable micro-waves.
Potential impact on many sectors
The newly-developed technique could be applied in many areas, in the field of fibre-optics, for measuring distances and time and for GPS location, and more generally for enhancing performance across the entire field of electromagnetics – including X-rays, radio waves and infrared. Whereas quartz suffers from aging and the consequent degradation of its resonance over time, laser beams are not susceptible to such unwanted variations. It can therefore be argued that the performance of the whole range of electronic information and communications devices in our digital society, which rely on the properties of quartz, will soon be enhanced by using a photon-based reference. Photon devices not only hold out the promise of savings in energy, materials, and therefore cost, but also have the capability of sending telecommunications signals over greater distances and with better data transmission quality.