Over the past decade or more, there has been a great deal of interest in the mechanical, electronic and optical properties of graphene. The interest in the optical properties of graphene stems largely from two key features of the electronic band structure: it is gapless and the dispersion is linear near the Dirac points where the two bands touch. Both features can be uniquely accessed using terahertz radiation, because, under the right conditions, it can strongly drive both interband and intraband transitions. In this talk, I will describe the formalism and computational results of our density-matrix approach to modelling the nonlinear terahertz response of graphene, including various scattering mechanisms. As I will show, in undoped graphene, a very large nonlinearity can arise due to the interplay between the intraband and interband transitions. I will finish by showing how a parallel-plate waveguide configuration containing graphene can be used to generate the third harmonic of a 2.0 terahertz incident field with a power conversion efficiency of up to 20%. If time allows, I will also discuss density functional results for the effects of impurities and strain on third harmonic generation in graphene.
Biography: Marc Dignam received his PhD in theoretical condensed matter physics from the University of Toronto in 1991 and held a postdoctoral fellowship at AT&T Bell Labs in Murray Hill (1991–1993), working under Nobel laureate Horst Störmer. In 1994, he joined MPB Technologies as an NSERC Industrial Research Fellow, modelling and designing fibre optic communication devices and systems. He was a professor in the Department of Physics, Engineering Physics & Astronomy at Queen’s University from 2000 to 2026 and is now a Professor Emeritus at Queen’s. Dr. Dignam’s research is in theoretical and computational condensed matter physics and optics. He has worked on the linear and nonlinear optical and terahertz response of semiconductor superlattices, quantum wells, and nanorods; the nonlinear terahertz response of monolayer and bilayer graphene; and nonlinear quantum optics in ring resonator and photonic crystal systems.
Add to Calendar
2026-09-10T10:00:002026-09-10T11:00:00The Nonlinear Terahertz Response of GrapheneEvent Information:
Over the past decade or more, there has been a great deal of interest in the mechanical, electronic and optical properties of graphene. The interest in the optical properties of graphene stems largely from two key features of the electronic band structure: it is gapless and the dispersion is linear near the Dirac points where the two bands touch. Both features can be uniquely accessed using terahertz radiation, because, under the right conditions, it can strongly drive both interband and intraband transitions. In this talk, I will describe the formalism and computational results of our density-matrix approach to modelling the nonlinear terahertz response of graphene, including various scattering mechanisms. As I will show, in undoped graphene, a very large nonlinearity can arise due to the interplay between the intraband and interband transitions. I will finish by showing how a parallel-plate waveguide configuration containing graphene can be used to generate the third harmonic of a 2.0 terahertz incident field with a power conversion efficiency of up to 20%. If time allows, I will also discuss density functional results for the effects of impurities and strain on third harmonic generation in graphene.
Biography: Marc Dignam received his PhD in theoretical condensed matter physics from the University of Toronto in 1991 and held a postdoctoral fellowship at AT&T Bell Labs in Murray Hill (1991–1993), working under Nobel laureate Horst Störmer. In 1994, he joined MPB Technologies as an NSERC Industrial Research Fellow, modelling and designing fibre optic communication devices and systems. He was a professor in the Department of Physics, Engineering Physics & Astronomy at Queen’s University from 2000 to 2026 and is now a Professor Emeritus at Queen’s. Dr. Dignam’s research is in theoretical and computational condensed matter physics and optics. He has worked on the linear and nonlinear optical and terahertz response of semiconductor superlattices, quantum wells, and nanorods; the nonlinear terahertz response of monolayer and bilayer graphene; and nonlinear quantum optics in ring resonator and photonic crystal systems. Event Location:
BRIM 311