ITMO, SPbGETU and Australian National University: Microwave Superresonator

2020: Microwave Ultra Resonator Presentation

On November 13, 2020, ITMO announced that a Russian group of physicists from ITMO Universities, SPbGETU LETI and the Australian National University created a microwave superresonator. The development will make it possible to produce highly efficient compact elements for microwave technology and optical computers. The work of scientists is published in Advanced Materials.

Most modern household appliances operate on the principle of controlling various waves - radio, acoustic, optical. With them, we heat objects, record and transmit information. An important element in such systems are resonators - devices that "catch" the incident wave and repeatedly increase its intensity. The quality of the technique designed to control light, sound or microwave oscillations depends on the properties of the resonators.

A good resonator, capable of effectively capturing and holding electromagnetic radiation, is usually large (compared to the wavelength of oscillations), but at the same time most modern devices require compactness. Physics of ITMO University, St. Petersburg State Electrotechnical University "LETI" and Australian National University (group prof. Yuri Kivshar) found a solution to this contradiction by creating a sub-wave resonator, with dimensions much smaller than the wavelength, capable of concentrating electromagnetic energy as efficiently as possible.

One of the main characteristics of the resonator is its quality factor, that is, the ability to store incident electromagnetic energy. Usually, the quality of the resonator fades very quickly with a decrease in its size. Therefore, it becomes an important task to create a compact and at the same time high-approval resonator. To solve this problem, we decided to resort to the use of the so-called connected states in the continuum, known from quantum mechanics, - says Mikhail Odit, employee of the New Physicist of ITMO University, associate professor of St. Petersburg State Technical University "LETI"

This phenomenon consists in the interaction of radiation of two connected resonances existing in the same system. It can lead to both amplification and complete suppression of the resonator radiation.

In our work, it has been shown that we can provide the geometry of the resonator in which the oscillations emitted by it in the far zone suppress each other. This occurs when the resonator forms two types of oscillations having a similar field shape and occurring at the same frequency. If the oscillations are mutually subtracted, then the resonator ceases to emit energy, which actually means a significant increase in its efficiency. At the same time, the device itself remains compact, - says Mikhail Odit, employee of the New Physicist of ITMO University, associate professor of St. Petersburg State Technical University "LETI"

To observe the described effect, it is necessary to correctly select the shape, size and material of the resonator. The researchers settled on a cylindrical device made of microwave ceramics with a large dielectric constant. But in order to select the size of the desired cylinder with the necessary accuracy, dozens of resonators of different sizes would have to be made. Therefore, the idea was proposed to make a small set of cylinders, the height of which would change twice with respect to the previous one. Thus, the height of the smallest cylinder was only a quarter of a millimeter, and the largest - 15 mm. By combining a set of these resonators, it was possible to collect the final sample of the desired height, while maintaining the accuracy of selecting the height of only ¼ mm.

As a result, scientists managed to find the optimal dimensions of the cylinder and experimentally observe superresonance states. At the same time, it was shown that already a 5% change in the height of the resonator led to a hundred-fold increase in its quality. In fact, the authors of the study managed to achieve the highest possible quality of the resonator for this material. It can only be made more efficient by offering an even more advanced dielectric with a lower absorption level.