What is it about?

A device operating on an exceptional surface is very useful for various applications, such as in the field of sensors and lasers. Here, we have realized a new device integrated in an optical chip that operates on an exceptional surface: the infinity-loop microresonator, which consists of an infinity-shaped microresonator coupled at two points to a bus waveguide.

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Why is it important?

This particular type of microresonator has a high degree of tunability and increases the sensing performance of a backscattering perturbation (caused, for example, by a molecule/particle on the order of tens of nanometers) compared to a normal microresonator. This is due to several factors: since the infinity is a closed structure, it resonates at some specific frequencies, the double coupling with the bus waveguide causes the coupling between the two counter-propagating electromagnetic fields inside the infinity-shaped waveguide to be asymmetrical, increasing the sensitivity of the system, moreover, the unique interference established between the electromagnetic fields inside the bus waveguide reduces the detection limit of a perturbation.


The high tunability of the infinity-loop microresonator enables new and exciting applications. Indeed, it can improve the performance of common sensors.

Riccardo Franchi
Universita degli Studi di Trento

Read the Original

This page is a summary of: The infinity-loop microresonator: A new integrated photonic structure working on an exceptional surface, APL Photonics, May 2023, American Institute of Physics,
DOI: 10.1063/5.0146639.
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