This article looks at two impressive breakthroughs from VTT MIKES in Helsinki that are shaking up precision timekeeping and optical sensing. First, there’s a record-setting strontium single-ion optical clock that’s redefining how accurately we can measure time and frequency—crucial for the SI second.
Then there’s the EPheS project, which is using metalenses and MEMS-based infrared filters to create small, ultra-sensitive tools for gas and material analysis. The potential here stretches across industries and environmental science.
Redefining the Second: Record-Breaking Optical Clock Performance
For decades, we’ve defined the second using microwave transitions in cesium atoms. But now, optical clocks—operating at much higher frequencies—are ready to take the lead, promising far better precision.
VTT MIKES has made a big leap in this direction. At the center of their work is a strontium single-ion clock. This device uses the quantum transition of a single trapped strontium ion as a remarkably stable reference “pendulum.”
The team in Helsinki recently set a new benchmark in absolute frequency measurements with this clock.
A new record in systematic uncertainty
The VTT MIKES group achieved a systematic uncertainty of 7.9×10⁻¹⁹ in their clock’s measurements. To put it simply, this means the clock would drift by less than one second over a span longer than the universe’s age.
Getting to this level of control takes painstaking attention to every possible influence on the ion: electromagnetic fields, blackbody radiation, relativistic effects, and even tiny shifts from trapping conditions.
Reliability and comparison with International Atomic Time
Precision isn’t enough—a reference clock has to be reliably available, too. Over 10 months, the strontium clock ran with an impressive 84% uptime, constantly measuring its frequency against International Atomic Time (TAI).
Keeping this kind of stability over months isn’t easy, and it really shows how mature the system is. The total uncertainty in comparing the optical clock to TAI was 9.8×10⁻¹⁷.
But here’s the twist: this limit didn’t come from the optical clock, but from the cesium clocks that currently define TAI. Optical clocks have now outperformed the cesium standards they’re measured against. Isn’t it time to redefine the second with optical tech?
EPheS: Compact Spectral Imaging and Gas Sensing for a Sustainable Future
While the optical clock project is about fundamental measurements, VTT is also pushing advanced photonics into real-world tech through the EPheS project.
Launched in early 2025 as a three-year effort, EPheS wants to shake up how we sense gases and analyze materials in real time. The main idea is to combine metalenses—ultra-thin, nanostructured lenses—with MEMS-based tunable infrared filters to build small, tough instruments that do high-performance spectral imaging and gas detection.
Metalenses and MEMS: Simplifying complex optics
Metalenses are flat optical components with tiny engineered structures that focus and shape light like traditional lenses. By replacing bulky lens stacks, they make devices:
Alongside metalenses, MEMS-based tunable infrared filters let you quickly pick out narrow wavelength bands. This tunability is key for infrared spectroscopy and photoacoustic detection, where the unique “fingerprints” of molecules in the infrared help identify and measure different gases and materials.
Real-time sensing and wide-ranging applications
EPheS wants to deliver instruments that do real-time, highly sensitive analysis with very little interference from background signals. By combining spectral imaging with photoacoustic techniques, these devices can spot trace gases or tiny material changes that would otherwise slip by unnoticed.
The possible uses are broad, cutting across several fields:
Collaborative Innovation and Industrial Readiness
EPheS is built on a strong partnership, blending research with industrial know-how. Besides VTT, the team includes Tampere University, Vaisala, Gasera, and Schott Primoceler. It’s also part of the Chip Zero ecosystem led by Applied Materials.
This setup helps make sure breakthroughs in science actually make it to the market. Soon, component fabrication will start in VTT’s cleanroom facilities, which are set up for 200 mm wafer processing.
That’s a big deal for scaling up: wafer-level production lets you combine complex optical and MEMS structures at costs and quantities that fit real-world industry needs.
Toward a More Precise and Sustainable Technological Landscape
The advances in optical clocks and compact spectral sensing at VTT share a common thread. They’re both about using cutting-edge photonics to reach unprecedented precision in measuring time and the world around us.
From redefining the second to enabling greener monitoring and diagnostics, these technologies open up high-end measurement for more people and industries. They make things more efficient and sustainable too—something we could really use right now.
As these systems move from lab prototypes to real products, they’re poised to shake up metrology and sensing. But it’s not just that—they could reshape science, industry, and how we care for the environment.
Here is the source article for this story: Finnish optical clock sets accuracy record and refines definition of second…