Two-laser design could shrink ultra-precise "light rulers" down to chip size
Researchers in New Zealand and the US have shown a chip-based optical frequency comb, built from two lasers, that performs the key jobs needed for portable atomic clocks and GPS-free navigation.
Physicists at the University of Auckland and the University of Maryland have built a chip-scale optical frequency comb using two lasers instead of one, a design that could help move the ultra-precise measuring tool out of the lab, the University of Auckland said. The work is reported in the journal Nature.
A frequency comb measures light the way a ruler measures distance
An optical frequency comb produces millions of evenly spaced, precisely known colours of light. Like the marks on a ruler, those colours can be used to measure time, distance and chemical signals with extreme accuracy. The technology underpins optical atomic clocks, the most precise clocks in the world, and earned John Hall and Theodor Hänsch the 2005 Nobel Prize in Physics.
The problem is that most combs are large and expensive, so they rarely leave the laboratory. Smaller versions on chips exist, but controlling and stabilising them has been difficult.
Two lasers an octave apart fill in the colours between them
Conventional designs start with one laser whose light cascades outward across the spectrum. The new approach reverses that. Two lasers are placed an octave apart, meaning one has double the frequency of the other, and the comb forms automatically by filling in the frequencies between them, as the team describes in its preprint.
Professor Miro Erkintalo, head of physics at Auckland, first predicted the effect in 2021. The team demonstrated it in 2024 with Grégory Moille and Kartik Srinivasan of the University of Maryland and the US National Institute of Standards and Technology. In the new paper, the chip performed the three core comb tasks: generating precise optical frequencies, producing low-noise millimetre-wave signals and reading out an optical clock.
“With this new approach, we finally see a viable path for their use in deployable atomic timekeeping, which is one of their most demanding and important applications.” — Grégory Moille, University of Maryland
Portable clocks could enable navigation without GPS
The university said portable optical atomic clocks could help map underground mineral deposits and support navigation systems that do not rely on GPS satellites. Other possible uses include timing in telecommunications networks and highly sensitive sensors.
Those uses are still some way off. In the paper, the authors write that cutting the size, weight, power and cost of combs could lead to mass production. Erkintalo, Moille and Srinivasan have filed a provisional patent application on parts of the work.
Good News Daily recently covered other precision optics work in new mirror coatings for the LIGO gravitational-wave detectors.
Like what you're reading?
Related stories
Australian Team Builds Ultra-Precise Optics to Help LIGO Detect Fainter Gravitational Waves
Researchers at the Australian National University spent three years making two specialized beamsplitters for LIGO, coated to within a nanometre or two across almost half a metre, for an upgrade that will make the detectors more sensitive.
Japanese Scientists Make DNA Strands Grow, Move and Link Into Networks Like Living Cells
Researchers at Institute of Science Tokyo and Kyoto University grew long DNA strands on protein tubes and used motor proteins to move them, forming networks within minutes, a step toward materials that can build and reshape themselves.
Researchers Used Quantum Vacuum Fluctuations to Raise a Superconductor's Critical Temperature by Up to 5.4%
Placing a thin superconductor inside a specially built terahertz cavity strengthened the quantum fluctuations of empty space around it and raised its critical temperature by up to 5.4%, a team at the University of Science and Technology of China reports.
