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Fiber optics gurus perfect highly precise microresonators

July 27, 13:35 UTC+3 MOSCOW
It is a step towards a new level of transmission quality and data processing
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©  Dmitry Rogulin /TASS, archive

MOSCOW, June 22. /TASS/ Two fiber optics specialists, Professor Michael Sumetsky from Aston University (UK) and Nikita Toropov, a researcher at the Center of Information Optical Technologies (CIOT) of ITMO University, have refined a new method in producing optical microresonators, unprecedented in precision. The microresonators will form a basis for maintaining quantum computers, as reported the press service of ITMO.

The study has been published in the journal, Optics Letters. "This technology does not require vacuum and is almost free from "wet" stages associated with circuit processing by corrosive solutions that considerably lowers the cost. Nevertheless, the main advantage is that this is a step towards a new level of transmission quality and data processing, needed for creating highly sensitive measuring devices and quantum computers," - clarified in the press release.

An optical (bottle) microresonator is a light trap structured as a tiny thickening of the optical fiber. As photons cannot be stopped, one has to invent a proper way to delay the photon current in order to use them for information storage. For that purpose, a series of bottle microresonators can be applied. The delay of the signal in such microresonators is due to the effect of a "whispering gallery": once inside the microresonator, a light wave is reflected from the walls and starts circulating. Due to the microresonator’s spherical shape, the light can circulate for quite a long time, which significantly slows down the proliferation of photons from one microresonator to another along the fiber.

The trajectory of light can be varied by changing the microresonator’s shape and size. Taking into account the typical size of a microresonator (smaller than a tenth of a millimeter), any change in these parameters must be very subtle and exact, since even the slightest defect on its surface can send the beam astray. "When light has been circulating for a long time it starts to interfere with itself," says Michael Sumetsky. "If an error crawls in during the fabrication of the microresonator, we lose control of the system. That is why there are two requirements that must always be met: a minimum deviation in dimensions of the microresonator and low light loss. Our microresonators comply with both."

The microresonators created by scientists from Russia and UK are produced in such a manner that the difference between their size does not exceed 0.17 angstrom. This variation in size is 10 times smaller than the diameter of a hydrogen atom and 100 times smaller than a nanometer. For comparison, microresonators’ current manufacturing precision is still measured on a nanoscale level.

To fabricate microresonators, several years ago, Michael Sumetsky introduced a new technology called SNAP (Surface Nanoscale Axial Photonics). The essence of the SNAP method lies in its controlled introduction of non-uniformities onto the fiber surface by a laser. It is crucial that the laser does not melt the fiber, but anneals it removing the strains frozen inside. When these strains disappear, the fiber swells a little and a microresonator forms. The researchers plan to fine-tune the SNAP technology and to broaden its application range.

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