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Time and frequency


Studying chip-integrated photonic systems for precision metrology, photonics and sensor technologies

We work on sensor technologies and optical frequency combs for optical metrology applications. We have a range of university and industry partners within the UK and Europe to accelerate the development of novel microresonator technologies for out-of-the-lab use.

Microresonator technology

NPL's infrastructure and cleanroom facilities enable us to fabricate ultra-high-Q optical microresonators. These resonators are micrometer-scale glass rings with diameters smaller than a human hair. Our microresonators can be integrated into silicon chips and store light for up to one million round-trips. The strong confinement of extremely high optical intensities in our ring resonators makes them an ideal platform to investigate interaction between photons. There are a large number of potential applications ranging from optical frequency comb generation to novel sensor technologies and precision metrology.


The Nobel Prize in Physics was awarded to Theodor Haensch and John Hall in 2005 for their work on optical frequency combs. These can be used to measure optical frequencies with unprecedented precision. A frequency comb consists of 1,000 to 100,000 individual laser frequencies that are evenly spaced and can be used as a ruler for measuring unknown optical frequencies. Conventional frequency combs consist of bulky pulsed lasers. An entirely novel means of generating optical frequency combs in microresonators was pioneered by Pascal Del'Haye by directly converting a continuous wave laser into a frequency comb using nonlinear frequency conversion. These microcombs paved the way to realise extremely compact frequency references for spectroscopy, telecommunication systems and read-out of optical clocks. NPL is working on applications of microcombs and on improving the fundamental understanding of the physics behind the comb generation process.

Symmetry breaking and interaction of counterpropagating light

NPL realised spontaneous symmetry breaking of counterpropagating light in ring resonators for the first time. In our proof-of-principle experiments we demonstrated that light above a certain threshold power can only circulate in one direction in our microresonators and not in both directions simultaneously. This effect can be used to realise chip-integrated optical diodes and novel sensor technologies that read-out the amount of clockwise and counterclockwise circulating light in ring resonators. In particular, our work enables enhanced near-field sensors and miniaturised optical gyroscopes.

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