Lasers are useful across a vast range of disciplines, from the optical characterization of materials for solar panels or LEDs, all the way up to inertial confinement fusion experiments. For decades, laser physicists and materials scientists have been grappling with how to improve their systems. Lasers have to balance a great many different requirements. They need to be powerful, ultimately focusable, stable, efficient and ideally tuneable to precise frequencies. In addition to this, for arrays of lasers, the array still needs to function even if parts or sub-elements of it fail.
The answer to this problem came from developments in fundamental theoretical physics. Recently, an area of great interest for condensed-matter theorists has been the study of topological insulators. The Nobel Prize was awarded two years ago to David J Thouless of the University of Washington, Duncan M Haldane of Princeton and J Michael Kosterlitz of Brown University for their research into how topology influences these exotic forms of matter.
New research hopes to establish topological lasers as the next big field of inquiry. The experimental aspects of the research were led by Professors Mercedeh Khajavikhan and Demetrios Christodoulides of the College of Optics and Photonics (CREOL) and their graduate students Steffen Wittek, Midya Parto and Jinhan Ren. A team from Technion in Israel that includes Moti Segev, Miguel Bandres, and Gal Harari initiated some of the theoretical aspects of the research; they have collaborated ever since.
These topological insulators carry ‘supercurrents’ on the surface, while the interior of the substance is an insulator. This surface current continues unidirectionally without being scattered by defects on the surface of the material. Understanding new processes of electron transport and their properties – characterizing them with both theoretical models and experiments – is key to a broad number of technological applications. Superconductivity is a classic example of exotic electron transport phenomena, with all of its theoretical and practical applications.
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