(NPL: Teddington, England) -- Scientists at the National Physical Laboratory recently published findings on laser frequency stabilization, demonstrating an unprecedented level of performance using an optical reference cavity. This advancement features a beyond state-of-the-art optical storage time and a novel approach to actively cancel spurious stabilization noise.

Frequency stabilization of lasers to optical reference cavities is a well-established method for achieving superior stability. The recent work significantly reduces technical stabilization noise, enabling lasers with enhanced stability performance. The team developed an optical reference cavity measuring an extraordinary 68 cm in length, achieving a record optical storage time of 300 microseconds. To put this achievement in perspective, the light trapped between the high reflectivity mirrors at either end of the 68 cm cavity can travel approximately 100 km, equivalent to twice the length of the Eurotunnel.

The 68 cm long optical reference cavity developed at NPL. Photo by Andrew Brookes.

In addition to the advancements in cavity design, the researchers tackled the challenge of spurious stabilization noise. They successfully implemented a technique to actively cancel a source of technical noise known as residual amplitude modulation (RAM), which arises from the phase modulation technique required for stabilization.

This innovative work paves the way for the development of more stable lasers, which will enhance the performance of optical clocks—the next generation of atomic clocks based on optical transitions. The implications of this research extend across various fields, including national timekeeping, positioning, navigation, telecommunications, characterization of laser sources, and fundamental science.

The findings underscore the potential for improved measurement capabilities that could lead to significant advancements in technology and scientific research.

Marco Schioppo, principal scientist, says, “We are glad to share these results on improved laser frequency stabilization to optical cavities to enable the development of better and better lasers. Since cavity-stabilized lasers are ubiquitous tools in high precision time and frequency measurements, our work will have a broad positive impact on a variety of technological applications and science.”

Adam L. Parke, assistant scientist, says, “This has been an interesting challenge to work on, and I’m glad to have contributed to this improvement in control of residual amplitude modulation, an effect that can seriously limit frequency stabilization if not properly managed.”

The publication has been selected as “Editors’ Pick” by the journal Optics Letters, a recognition given to highlight articles with excellent scientific quality. It’s available here.

Adam Parke (front) and Marco Schioppo in their laboratory at NPL. Photo by David Severn.