New Ways to Twist and Shift Light

Researchers from the National Physical Labora­tory NPL have revealed unusual qualities in light that could lead the way to entirely new elec­tronic devices and appli­cations. Light is used extensively in electronics for tele­communi­cations and computing. Optical fibres are just one common example of how light is used to faci­litate telephone calls and internet connec­tions across the globe. Now, NPL researchers inves­tigated how light can be controlled in an optical ring resonator, a tiny device that can store extremely high light inten­sities. Just as certain whispers can travel around a whispering gallery and be heard the other side, in an optical ring resonator wave­lengths of light resonate around the device.

For the first time researchers analyze the interplay of two types of spontaneous symmetry breaking that can occur simultaneously in optical ring resonators. (Source: NPL)

The first-of-its-kind study uses optical ring reso­nators to identify the interplay of two types of spon­taneous symmetry breaking. By analysing how the time between pulses of light varied and how the light is polarised, the team has been able reveal new ways to manipulate light. For instance, usually light will obey what is known as “time reversal symmetry”, meaning that if time is reversed, light should travel back to its origin. However, as this research shows, at high light inten­sities this symmetry is broken within optical ring reso­nators.

Francois Copie, scientist on the project, explains: “When seeding the ring reso­nator with short pulses, the circulating pulses within the resonator will either arrive before or after the seed pulse but never at the same time.” As a potential appli­cation, this could be used to combine and rearrange optical pulses, for example in telecommu­nication networks. The research also showed that light can spon­taneously change its polarisation in ring reso­nators. This is as if a guitar string was initially plucked in the vertical direction but suddenly starts to vibrate either in a clockwise or an anti­clockwise circular motion.

This has not only improved our under­standing of nonlinear dynamics in photonics, helping to guide the develop­ment of better optical ring resonators for future appli­cations such as in atomic clocks for precise time-keeping, but will help scientists to better understand how we can mani­pulate light in photonic circuits in sensors and quantum tech­nologies.

Senior Research Scientist Pascal Del’Haye said: “Optics have become an important part of our telecoms networks and com­puting systems. Under­standing how we can mani­pulate light in photonic circuits will help to unlock a whole host of new tech­nologies, including better sensors and new quantum capa­bilities, which will become ever more impor­tant in our everyday lives.” (Source: NPL)

Reference: F. Copie et al.: Interplay of Polarization and Time-Reversal Symmetry Breaking in Synchronously Pumped Ring Resonators, Phys. Rev. Lett. 122, 013905 (2019); DOI: 10.1103/PhysRevLett.122.013905

Link: Microphotonics Research Lab, National Physical Laboratory NPL, Teddington, United Kingdom

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