The Waterloo Institute for Nanotechnology (WIN) has launched a new seminar series, Quantum Nano Collision (QNC) Seminar Series, to deepen the engagement of the Waterloo researchers who work at the interface of quantum and nanotechnologies. This seminar series will also provide opportunities for senior graduate students, post-doctoral fellows, and research associates to present their innovative work along with the faculty members to bring together the excitement around these cutting-edge technologies that would shape our future.
The next talk for the QNC Seminar Series will be delivered by Professor Zbig Wasilewski.
Registration is required. If you have any questions or issues registering, please contact firstname.lastname@example.org
Towards room temperature, compact sources of coherent terahertz radiation
The so-called terahertz gap (~1–10 THz) has received much attention over the last two decades because of many potential applications waiting for compact, portable terahertz radiation sources. The report of the first  terahertz quantum cascade laser (QCL) in 2002 brought much hope to the community. However, the possibility of ever reaching room temperature operation was considered unlikely by many. Indeed, after a slow ascent of the maximum operating temperature to 200K in 2012,  the progress in the field stalled for close to a decade. However, the recent demonstration of GaAs/AlGaAs THz QCL lasing up to 250 K,  brought back the vigor to these pursuits. Indeed, with the current understanding, no hard physical obstacles would preclude achieving lasing action at still higher temperatures.
Nevertheless, the prolonged stagnation in terahertz QCL progress inspired many to look for alternatives. Our research group has embarked on a parallel pursuit of a coherent terahertz light source based on a very different principle, namely the polariton lasing mechanism – more analogous to Bose-Einstein condensation than conventional lasing, but with a similar end result – in arrays of AlGaAs parabolic quantum wells.  Albeit demonstration of coherent terahertz radiation at 300 K from such quantum systems may be still years away, the research has already produced important results furthering our understanding of plasmons and evidence of polariton formation up to 200 K in the dispersive cavities necessary for polariton scattering.
This presentation will outline the physics behind both types of terahertz sources, show the current status of research in these projects, and discuss the key challenges ahead.
 R. Kohler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, "Terahertz semiconductor-heterostructure laser," Nature 417, 156-159 (2002). https://www.nature.com/articles/417156a
 S. Fathololoumi, E. Dupont, C. W. I. Chan, Z. R. Wasilewski, S. R. Laframboise, D. Ban, A. Mátyás, C. Jirauschek, Q. Hu, and H. C. Liu, "Terahertz quantum cascade lasers operating up to ~ 200 K with optimized oscillator strength and improved injection tunnelling", Opt. Express 20, 3866-3876 (2012). http://www.opticsexpress.org/abstract.cfm?URI=oe-20-4-3866
 A. Khalatpour, A. K. Paulsen, C. Deimert, Z. R. Wasilewski, and Q. Hu, "High power portable terahertz laser systems," Nature Photonics 15, 16-20 (2021). https://www.nature.com/articles/s41566-020-00707-5
 C. Deimert, P. Goulain, J. M. Manceau, W. Pasek, T. Yoon, A. Bousseksou, N. Y. Kim, R. Colombelli, and Z. R. Wasilewski, "Realization of Harmonic Oscillator Arrays with Graded Semiconductor Quantum Wells," Phys. Rev. Lett. 125, 097403 (2020). https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.097403
Zbig Wasilewski is a Professor in the Electrical and Computer Engineering Department, cross-appointed to the Department of Physics and Astronomy at the University of Waterloo. Dr. Wasilewski is also a core member of the Waterloo Institute for Nanotechnology and has an Associate Faculty position at the Institute for Quantum Computing. He is internationally renowned for his contributions to the field of Molecular Beam Epitaxy, quantum-dot and quantum-well photonic devices, and quantum structures and devices based on high mobility 2D electron gases.
Dr. Wasilewski earned his doctoral degree from the Institute of Physics of the Polish Academy of Sciences in 1986, based on his pioneering research in low-temperature magneto-optical studies of semiconductors under high hydrostatic pressures. In 1988, after a post-doctoral appointment at the Imperial College, London, he joined the National Research Council of Canada (NRC), shifting his research focus to molecular beam epitaxial growth and characterization of quantum structures and devices based on III–V semiconductor compounds. In 2006, Dr. Wasilewski was promoted to Principal Research Officer – NRC’s top research rank. In July 2012, Dr. Wasilewski joined the University of Waterloo as a Full Professor and the University of Waterloo Endowed Chair in Nanotechnology, where he established the Quantum-Nano Centre MBE Facility (QNC-MBE). The same year, he was awarded the life title of Professor of Physics by the President of Poland in recognition of his role in developing the field of GaN-based optoelectronics in Poland. Dr. Wasilewski coauthored over 350 refereed journal papers with an h-index of 62 and more than 15,000 citations to his work.