Researchers Develop Fundamental Component of Photonics

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It follows one article published day (03/13) in the english website of the Agência FAPESP highlighting that an international group of researchers including three Brazilians has developed a fundamental Component of Photonics.

Duda Falcão

Researchers Develop Fundamental

Component of Photonics

By Elton Alisson

13/03/2013

A new device could be used

in the defense and aerospace

industries. The study was

featured on the cover of

Nature Materials

Agência FAPESP – An international group of researchers including three Brazilians has developed a device that could make it possible to produce a fundamental but as yet unavailable component of photonics (the field involving materials such as optical fibers that produce, transport, and detect light).

They showed in experiments how the device operates on a micrometer scale (equivalent to one millionth of a meter) that is compatible with the manufacturing process used in the semiconductor industry. It can reflect optical waves (in the form of light) unidirectionally and at the same frequencies used today in the fields of fiber optics and telecommunications. The study was featured on the cover of February’s edition of the journal Nature Materials.

“We have been trying to develop this component since the 1990s. It will allow for a new class of devices and make way for the construction of a number of systems inside one optical circuit,” said Coronel Airman Vilson Rosa de Almeida, director of the Institute for Advanced Studies (IEAv), professor at the Technological Institute of Aeronautics (ITA), and one of the authors of the study, to Agência FAPESP.

“Now, we have developed it, and it’s integrated into a single optical circuit and compatible with the semiconductor industry,” he affirmed. ITA professor José Edimar Barbosa Oliveira was a coauthor of the article and carried out a Thematic project on optical-electronic devices with FAPESP funding.

According to Almeida, photonic devices (which can transport information in the form of light) began to be used together with electronic devices in microchips over the last decade, leading to the field of silicon photonics.

Since then, many components essential to the construction of an optical circuit have been created, such as filters and light beam splitters, to connect optical fibers to microchips and enable the component to process information in the form of light.

The demonstration of the concept used in the newly developed device, however, could contribute to the creation of one of the building blocks still missing for the realization of optical computing: an optical isolator that controls the flow of light used to carry out unidirectional logical operations.

“The idea is to continue the experiments and develop a complete optical isolator and other basic devices that we still don’t have for building photonic circuits that are compatible and integrable with materials used in the semiconductor industry,” he explained.

Microchip-Compatible Material

Almeida said that devices similar to the newly developed one have been demonstrated before. However, the existing components are built on a centimeter scale and are not made of passive materials (meaning they do not allow optical gain). Therefore, they are neither compatible nor integrable with the CMOS fabrication process used in the semiconductor industry.

“This manufacturing process, which was adopted decades ago by the semiconductor industry, only allows for the use of materials such as silicon, silicon oxide, and some metals. So, to develop silicon photonics, new devices have to be compatible and integrable with the materials already used by microchip manufacturers,” explained Almeida.

The new device developed by the international groups of researchers is made of silicon, silicon dioxide, germanium, and chromium—all passive materials that are compatible with the CMOS process.

The component used is 20-30 microns wide. However, according to Almeida, it could be optimized by making it even smaller. “There are companies overseas specialized in developing devices for silicon photonics that could already use this component that we just developed,” he said.

Invisibility Cloak

In addition to microscopic applications in photonics, Almeida says the way the device is made and its ability to reflect light in one direction means it could also be useful on a macroscopic scale. These include the development of photonic sensor devices and systems and so-called invisibility cloaks, which have many uses, including defense and aerospace applications.

Because the component can reflect light in only one direction, it allows for “invisibility” in the opposite direction. Aside from this, it allows electromagnetic waves used for communication to pass in both directions.

This means new materials could be synthesized based on the principal demonstrated by the device. These new materials could be used to develop structures for vehicles that would be able to reduce or cancel out the reflection of radar waves emitted in a determined frequency range by an enemy vehicle, for example. At the same time, it would allow the vehicle’s occupants to communicate with the world outside.

“The fact that the device was developed with relatively common materials that are innocuous to human health and air safety, for example, makes these possible applications even more viable,” commented Almeida. “But the gamut of possible applications this device could have still hasn’t been fully investigated,” he noted.

International Collaboration

The study is the result of collaboration between researchers at IEAv and ITA together with a group from the California Institute of Technology (Caltech) in the United States and Nanjing University in China. Researchers at IEAv, where research in photonics has been underway for over 30 years, sent ITA Electronics and Computational Engineering doctoral candidate William dos Santos Fegadolli to Caltech for a study program in 2011. At the time, the photonics research team lead by Professor Axel Scherer at the North American institution was carrying out a similar study that had not achieved the results for which they hoped.

During Fegadolli’s stay at Caltech, IEAv and ITA researchers helped the team in California direct the experiments in such a way that they were able to achieve the results described in the Nature Materials article.

“The experimental part having to do with the manufacture and character of the new device was carried out by Fegadolli at Caltech. But his preparation, which enabled him to go to Caltech, was done at ITA and IEAv,” said Almeida, who is Fegadolli’s doctoral studies advisor. Fegadolli’s co-advisor is ITA Professor José Edimar Barbosa Oliveira.

Invitation to Stay in the USA

Fegadolli is expected to defend his thesis at ITA in March. He has been invited by Professor Scherer to be a permanent member of Caltech’s photonics research team because of the work he carried out during his stay there. The Brazilian researcher has received a number of other proposals in the photonics field aside from the prestigious Caltech invitation from renowned American universities and research centers.

“I have sought out other unidirectional characteristics in devices compatible with CMOS technology,” stated Fegadolli. “I’ve also researched the area of integrated sensors and systems based on silicon photonics used to aid medical diagnosis through microchip technology. This technology is very promising and promises to revolutionize the field of medical diagnosis in coming decades through a multidisciplinary approach,” he affirmed.

In Almeida’s opinion, Fegadolli still has much to contribute to the advance of research in photonics. “We will most likely hear his name in connection with the production of many photonics devices in the near future,” he predicted.

The article Experimental demonstration of a unidirectional reflectionless parity-time metamaterial at optical frequencies (doi: 10.1038/NMAT3495) by Fegadolli and others can be read by Nature Materials subscribers at: www.nature.com/naturematerials.

Source: English WebSite of the Agência FAPESP