Evrim Yazgin
Cosmos science journalist
A new device combines circuit designs to efficiently measure light. The compact “frequency comb” could lead to new technologies used in telecommunications, environmental monitoring and astrophysics.
Frequency combs are like rulers – for measuring light. They can take a light source – like radio waves or microwaves – and measure the frequency of the light. The frequency of light is how much the light wave oscillates in space.
Frequency is measured in Hertz (Hz). For example, AM radio waves usually lie in the frequency range 535–1605 (kHz, or thousand hertz). FM radio waves are about 88–108 megahertz (MHz, or million hertz).
Being able to measure the frequency of light has lots of benefits.
Frequency combs could be used for ultra-precise spectroscopy to determine the kind of light coming from distant stars and galaxies. High-precision spectroscopy can also be used in analysing molecules and atoms and determining the make up of different compounds, gases or other mixtures.
They could also be used to make extremely accurate clocks and act as a bridge between lower radio frequencies of light and much higher frequency light waves, enhancing the power of systems like GPS.
Electro-optic frequency combs were first introduced in 1993. The fell out of favour, however, due to their high power demands and limited bandwidth. In their place, engineers have relied on lasers and other kinds of optical combs. These devices are effective but also need a lot of power and require complex tuning.
A new device described in a paper published in Nature might see the electro-optic frequency comb leapfrog other tools in innovating optical technology.
The device uses a lithium tantalate platform. Using this material, the researchers were able to produce a frequency comb covering a 450nm spectrum of optical wavelengths – the widest range to date. It also operates stably across 90% of its range, reducing the need for complex tuning.
Further, the team was able to achieve this while also using 20 times less power than previous
The researchers say their device is a step forward in electro-optic frequency combs being used in applications which require precise laser ranging, like robotics, and accurate gas sensing, like environmental monitoring.
