Carlo Sirtori's team at the Laboratoire Matériaux et Phénomènes Quantiques (MPQ, materials and quantum phenomena laboratory) working with Thales R&T and Cambridge University (UK) have developed a technology that now makes it possible to inject terahertz (1012 hertz) waves into optic fibers and transfer them over hundreds of kilometers. These waves are in the far infrared range, between medium infrared and microwaves. For a long time, they were largely unknown. They have the characteristic of penetrating a large range of nonconductive materials. They can go through skin, clothing, paper, wood, cardboard or plastic, heralding numerous applications in the medium to long term (medical imaging, security and the environment).
Although the development of quantum cascade lasers (QCL) in the nineties made the continuous generation of terahertz waves possible, the waves had the drawback of being strongly absorbed by water vapor molecules once they were transmitted through the air. So the MPQ laboratory researchers and their colleagues at Thales R&T and across the Channel came up with the idea of bringing together cutting-edge telecommunications and QCL technologies. They figured out how to inscribe terahertz waves on the invisible electromagnetic waves of telecommunications. Thus, a telecommunication beam injected into a terahertz laser cavity propagates inside the cavity, mixes with the terahertz waves and memorizes their properties (phase and amplitude). As a result, the researchers obtained a telecommunication beam that transfers terahertz waves and then injects them into an optic fiber that protects the waves from water vapor molecules and carries them through the air over hundreds of kilometers. The research should also lead to improved QCL technologies.
