“What we did is going against the odds, going against common knowledge,” says Distinguished Prof. Mordechai (Moti) Segev of the Faculty of Physics. Prof. Segev was referring to the most recent papers, two groundbreaking back-to-back works on Photonic Topological Insulator Lasers published in the prestigious journal Science. This work, says the trailblazing professor, is: “possibly the most important thing I ever did.” This is no small statement by the award-winning Robert J. Shillman Distinguished Professor of Physics.
Topological insulators are one of the most innovative and promising areas of physics in recent years, providing new insight into the basic understanding of protected transport. These are special materials that are insulators in their interior but conduct a “super-current” on their surface: the current on their surface is not affected by defects, sharp corners or disorder; it continues unidirectionally without being scattered.
The researchers found a way to use the properties of photonic topological insulators to build a new type of laser which shows a unique fundamental behavior and greatly improves the robustness and the performance of laser arrays, opening the door for a vast number of future applications.
“Our research opens the door to many fundamental questions in science but also for exciting applications,” says graduate student Gal Harari. “One of these applications is a long standing problem in laser science and it is how to take many single emitters and coherently combine them together.”
“This new laser system went against all common knowledge about topological insulators” said Segev. “In a nutshell, the unique robustness properties of topological insulators were believed to fail when the system contains gain, as all lasers must have. But we have shown that this special robustness survives in laser systems that have a special (“topological”) design, and is able to make the lasers much more efficient, more coherent, and at the same time immune to all kinds of fabrication imperfections, defects and alike. This seems to be an exciting avenue to make arrays of miniature lasers work together as one: a single highly coherent high power laser.”
In their research, the scientists built a special array of micro ring resonators whose lasing mode exhibits topologically-protected transport – light propagates in one direction along the edges of the laser array, immune to defects and disorder and unaffected by the shape of the edges. This in turn, as they experimentally demonstrated, leads to highly efficient single-mode lasing that lasts high above the laser threshold.
The studies were conducted by Dist. Prof. Moti Segev and his team: Dr. Miguel A. Bandres and Dr. Gal Harari; in collaboration with Profs. Demetrios N. Christodoulides and Mercedeh Khajavikhan and their students Steffen Wittek, Midya Parto and Jinhan Ren at CREOL, College of Optics and Photonics, University of Central Florida, together with scientists from the US and Singapore.
The researchers demonstrated that not only are topological insulator lasers theoretically possible and experimentally feasible but that integrating these properties creates more highly efficient lasers. As such, the results of the study pave the way towards a novel class of active topological photonic devices that may be integrated with sensors, antennas and other photonic devices.