Photonic crystal devices

The research undertaken by Francisco Falcone in his PhD involved analysing the application of metamaterial structures in conventional high-frequency planar technology.

For his thesis Francisco Falcone analysed two types of structure. One with photonic crystals which have good control of the signal but are not greatly efficient with respect to size. These are known as Electromagnetic Bandgap (EBG) structures.

Taking these as a basis, Francisco Falcone put forward a number of microstrip technology devices, etching a periodic pattern on their planar surfaces. This is the most significant difference in these proposed, smaller and more compact unidimensional structures, compared to the previous, bidimensional ones. Moreover, they have experimented with the introduction of a resonator in planar technology.

First worldwide

It is, nevertheless, it is with the second type of structure where the results of the research team at the Public University of Navarre are more spectacular. What are known as left-handed metamaterials involve materials which have curious electromagnetic properties and which are not found naturally, i.e. they are artificially generated media.

In this part of the research Francisco Falcone synthesised left-handed materials in planar technology by using Split Ring Resonators (SRR) together with a medium of fine metallic wires. In this respect we can say that we have achieved the very first implementation worldwide of a low loss LHM metamaterial. An evolution of this device was the use of a new particle therein - which we call complementary SSR - in which the role of paper and metal is interchanged.

In this way and applying classical metamaterial concepts, we obtained devices with extremely low losses. Our proposal was based on the introduction of particles in planar technology, i.e. their integration into the circuit. In fact, we have managed to obtain the devices with the lowest losses ever obtained worldwide. We were the first to propose this phenomenon and the discovery received recognition on being published in the prestigious scientific magazine, Physical Review Letters.

The advantage of its use is that it enables the making of a series of circuits that otherwise would be impossible and, moreover, these give quite an optimal response in that they have few and very low losses.

This PhD puts forward the potential use of these kinds of structures for devices such as filters, couplings and aerials for 2nd, 3rd and 4th generations mobile communications systems such as satellite systems and WLAN. But, above all, they are low cost structures and very easy to manufacture.

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